I 100% agree with the beginning! My team is extremely new, and this channel has helped me and my partner heavily on how to build and to understand Science Olympiad Bridges. Thank you!
Thank you for the kind feedback! Teams like yours are exactly why I started this channel. Feel free to reach out if you have any specific questions and good luck this season!
What did the Daniel Wright MS bridge of 2015 look like? Was it a similar design? Was it shorter than the 15cm min height of this year? Did it actually hold full load or was it even lighter than 3.06g? their 4906 seems astounding and unreal.
Hi Bruce, I got your email, so I'll answer in more detail there. The short version is that I wasn't at 2015 Nationals, so I never got to see Daniel Wright's bridge. I would be shocked if it weren't shorter than what we had to do here as there was no height requirement. A 4900+ actual efficiency bridge is very, very impressive. I have only ever built one that was better and that was at much more than 15kg.
Absolutely amazing build! You inspired me and my partner so much! We think we have our final design at at weight of 3.36 scoring 6013 (assuming 15.1kgs of sand). We completely agree with you about the strategy aspect of this competition this year. Our bridge currently has a success rate of about 55% but we were looking at a design with a weight of 3.51 which works about 85% of the time. Me and my partner are still torn up about which bridge we should take to our state competition. Thank you again for your amazing deisign (it was a great starting point for us). And also we wish your team good luck in your state contest!
Thanks for the great feedback! Congrats on being able to replicate and improve on the build. Yeah, choosing the proper strategy is a critical part this year. Good luck at your state competition. BTW, I don't really have a home team anymore as my daughter is now in college. I'm rooting for everyone equally now!
Thank you! Your videos have been crucial to me and my partner, especially the density vs efficiency video! We wouldn’t be able to do it without you, we’re leaning on using the lighter design and going for it.
@@EmmettFerguson-rs9dw Thanks! I'm really glad you and your partner find my videos helpful. If your bridge is 3.36g, even if it fails early, it could still score > 4300, so not terrible by any means. It's a tough choice though. Let me know how it goes! Good luck!
Just wrapped up our season. Although we could not break 5900, we broke 5800. Maybe we could get there if we qualified for Nationals. We saw lots of Balsa Engineering copies.
Hi! I'm new to build in Sci Oly and was wondering if our bridge could hang off the end of the test support? Thank you so much, this channel is already helping me immensly.
Thanks for the kind words! I'm pretty sure that would be OK, but you want to try and make your bridge smaller to just fit otherwise you are using too much material which makes it heavier without any benefit. Good luck this season!
Hi, First of all, Thanks you so much for creating this helpful video. Your demonstration really have made our life easier to build bridge. we made a 7.05g bridge with following your design and guideline. After putting 3kg weight it broke. Only we didn’t use the specialized balsa. Can you please help me understanding what went wrong? We are planning to make again one for state. It’s for division B.
Hi! Most likely it was an issue with your gluing technique or perhaps it not being level. It's pretty much impossible for me to help without seeing some pictures of your bridge. Feel free to reach out to: mklinger at comcast dot net and I'd be glad to take a more close look at your bridge and offer some suggestions.
Can you shine light on the reasoning behind the tapered legs vs a square build. My son built 3 bridges of similar design to yours differing construction methods and material thicknesses slightly in each but not tapered and they’ve performed terrible. Barely holding 9000. Im assuming a jig helps hold these tapered angles true? Do you have any recommendations in jig building? Thank you for putting together a channel that is so helpful to teams. I’ve learned a lot and in turn that allows me to help my son with his builds.
Hi! The main reason to use a tapered design is for added lateral stability and less mass as the cross member pieces are much smaller as it tapers at the top. It does really help to have an assembly jig if you are attempting a tapered design or even a squared design for that matter. 3D printing is the best way. Think of it in 3 parts, the middle piece and then the 2 bottom pieces which get glued on. It would be better to print it all as a single piece, but not many printers can handle pieces that big (mine can't). If you check out the 3:05 point of this video, it shows several assembly jigs which can give you an idea on how to design and build them. th-cam.com/video/0tzcp99kzdk/w-d-xo.html If you don't have access to a 3D printer, even building something simple with wood or Lego would be better than nothing at all. Good luck!
Hi! Thanks for the positive feedback! I made an entire video on how to create a balsa library. I show a lot of cutting techniques as well. Give this a watch when you get a chance: th-cam.com/video/bLsTOpmozGI/w-d-xo.html Good luck at States!
Hey there, how can you make it this bridge so light because 1 stick of the leg (thick light balsa) is averagely 5 grams. Also what type of wood and dimensions did you use for the legs. Thank you and nice video!
Thanks for the positive feedback! The short answer is to use lighter wood. Balsa comes in a huge range of densities. For this build, I used 3/32" thick by 8mm and each of the 4 normalized pieces I used to make the legs were 30.5 cm and they weighed around 0.8g each. Each final leg piece was about 0.61g. You might like this video I made on density vs efficiency for some more insight: th-cam.com/video/mzMFhd4SqP8/w-d-xo.html
God damn, 3.39 and over 15kg of weight???, my first bridge was unmeasured, and I put like 6 braces + 2 verticals of tension, making it weigh 6.52 g and hold 15 kg, giving it efficiency of 3067. But holy 5900 efficiency? thats almost double the standard for the bridges that had to carry moving weights.
p.s tbh, my coach told me to do 3-5 braces (not counting verticals), I think I can get my bridge designs down to 5gms and still hold the 15kg. My first bridge broke cuz my leg accidentally hit the bucket T-T ~ I know not to do that anymore-
Yep, this build was pretty insane! This is probably very close to the upper limit of what is possible. It's always nice to see what can be done to have something to compare with. Good luck with your builds, your 3067 is a very good start!
3-5 cross braces is a good suggestion. This bridge has 5, so that is obviously what I found to be the best. Vertical trussing to the tension members isn't necessary with this type of design for most leg choices. Good luck as you build more, definitely let me know how it goes!
This particular build used all C-grain balsa. While that might be the best possible choice, especially for the legs, it's definitely not required for great results. I have built several 4500+ actual efficiency bridges that didn't use any C-grain in previous years. Equally important is having a well balanced bridge (all legs nearly identical mass) and built as perfectly level in both directions as possible.
Hello I have a question! Our team is fairly new and we were wondering where you buy your wood and what density of balsa wood you would recommend using. Thank you! :)
I like to use Specialized Balsa for my balsa: specializedbalsa.com/products/balsa_sheets.php and Fnabco for bass: fnabco.com/collections/basswood-sticks In general, start with "Light" or "Medium" density balsa
Do you think a single laser-cut sheet of 1/16 or laminated 1/32 basswood on both sides would weigh less and support equal weight? Do you think it would be enough improvement in efficiency to warrant the trouble?
They definitely wouldn't weigh less, especially the laminated option. The glue layer adds a lot of weight. For this bridge, I was using very light, highly optimized pieces of C-grain balsa. Regarding laser cutting in general, while it'd be really fun to play around with a nice one, I don't think it would help in most cases. I see a couple big problems. If you managed to cut a side from a single sheet, first it would be really expensive as you'd be wasting most of the entire sheet. Next, the grain alignment would be totally different which might cause problems, and most importantly, the density and thus strength is not consistent throughout an entire sheet, so a side cut from a single sheet wouldn't have balanced legs. That is a big key to getting the bridge fully optimized, especially at this level of mass. Laser cutting might be very useful for smaller, more intricate pieces, like the platform pieces I'm using for the Div C design this year, but even then, it probably wouldn't justifying buying a nice $5000 CO2 laser cutter.
I like to use 50 cps CA glue. This is the exact bottle, but you definitely wouldn't want to buy that much for a single person building: www.amazon.com/gp/product/B07DK19W6M/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 I also have an entire video on glue and gluing techniques that might be interesting for your daughter to watch: th-cam.com/video/55lb2KzSiwg/w-d-xo.html
Hi! Probably the best example of seeing how this jig gets assembled is from one of my other videos where I use very similar jigs. Check out this spot in the Part 3 of my optimization video. The jig for this season is put together exactly like this. Basically just glue the 3d printed parts together. I like to use PL3 construction adhesive for that. th-cam.com/video/0tzcp99kzdk/w-d-xo.html
Hi it's me again. I noticed you have 1/20 by 1/20 bass for your cross member, where do you source the wood? I've searched fnabco, but can't seem to find them.
Hi! I am looking st this build and wondering at the very top what was the width from each side of the bridge. basically i was wondering what the width was at the top.😂
@@balsaengineering6686 thanks for the quick reply i just need it to be atleast 500 efficiency to pass 😅also is the height 24.6cm right? and how long are the legs
@@rk741 I would recommend drawing out your requirements on a sheet of graph paper to figure that out. That is basically what I did with this design. The Div B rules for 2022-2023 specified that the loading block height needed to be at least 15cm spanning 35cm. If you want the duplicate this design, you can download the side STL jig files linked in the description of this video as well as the assembly jig.
@@rk741 You could bring them into a 3d viewer and examine them to try and come up with something to use as a jig. It really helps to have some kind of assembly jig for these types of devices. If you don't have or know someone with a 3d printer, you can get them printed as a service, but I have not done that myself.
@@balsaengineering6686 all bass wood? THANK YOU for making these videos! Our team last year consisted of 9 and 10-year old girls who were able to watch your videos and build some pretty amazing bridges! They walked away with medals and lots of high fives from the test proctors! I questioned giving blades and Sharpies to young kids, but they were responsible and did AMAZING... thank you!!
@@_JusticeBruv_ Hi! Thank you so much for the positive feedback! Hearing stories like yours makes all the hard work worth it and is exactly why I started this channel in the first place! Regarding this build, it's all balsa except for the primary tension members which were bass wood. Good luck this season!
@@balsaengineering6686 You're a lifesaver. We made a 10 gram bridge with a similar design and we got 3rd place in regionals. When we really pushed it, it held 55kg! We're now going with the 4 gram bridge now since our team made it to state!
@@indigo9971 The primary tension members are the bottom parts of the triangle sides. I would highly recommend you start with watching my Getting Started video carefully. In that video, I create an entire Div B bridge from a single sheet of balsa which can be very competitive. I go through all the details of each piece during the build: th-cam.com/video/7MwflLa5kCg/w-d-xo.html
Hi! When you assemble the jigs, is there a gap between the two triangular prices (the ones that make up one side?) Also, what would you recommend for cutting balsa? We were using an x-acto knife and balsa cutter, but noticed while cutting perpendicular to the grain it was showing a lot of resistance, causing our wood to splinter, bend, etc.
No, there shouldn't be a gap between the triangular jig pieces, try to glue them as tightly together as possible. I like to use the miter cutter from fourmost products for most of my balsa piece cutting (not stripping from sheets, but for cutting the pieces after that). Here is a link to their product if you can get one, it helps a lot: www.fourmostproducts.com/our-products/construction-tools/ If you mean stripping the balsa sheets, one trick is to snip off the end of the x-acto blade which makes it more stuff. You can see that in my balsa library video around the 3:45 mark: th-cam.com/video/bLsTOpmozGI/w-d-xo.html
@@balsaengineering6686 Hi! Thank you so much for replying. This actually helped us construct our very first bridge today, which ended up weighing around 6.2 grams. We were wondering how to tone down the weight even further. We used epoxy glue. While stripping the balsa, we noticed that the strips tended to vary in weight quite a lot (ranging from 0.6gto 1.2g) even though they were from the same sheet of balsa. Is this normal? Would baking help decrease this weight? What are the conditions you used for baking your bridge? Also, we used basswood for our primary tension member, so to decrease the weight would you recommend making the whole thing out of balsa?
@@avnigupta3393 Hi! Congratulations on building your first bridge! 6.2g is not bad. I would highly recommend using CA glue over epoxy. Stick with bass for your primary tension members, especially if you have 1/32x1/16 available. To answer your other questions, yes, the density variation in the sheets is normal. It's so common I made an entire video on it: th-cam.com/video/bLsTOpmozGI/w-d-xo.html and for baking the bridge, I made an entire video that goes over that and more for competition prep: th-cam.com/video/6zOvHMZLaNE/w-d-xo.html you might also benefit from my gluing video: th-cam.com/video/55lb2KzSiwg/w-d-xo.html Good luck!
@@balsaengineering6686 hi! Thanks so much for responding again. Do you know where we can acquire testing apparatus for the bridge (specifically the loading block) Also, there is a slight bend when you glue the cross members. The top cross member causes the bottom cross member to bend. Does this affect our build? Will it affect how the build performs?
@@avnigupta3393 Hi! I know you can buy the professional testing rig here if you want: www.balsawoodhoppers.com/ It's pretty expensive and I think there is a pretty long lead time. Most teams just build something that works by putting a piece of wood between two tables and hand-loading the sand. For the loading block, just cut a 5cm x 5cm x 2cm block of wood and drill a hole in the middle. Or if you have access to a 3D printer, it's pretty trivial to print a loading block that size. Good luck!!
Hi! The primary tension members of this bridge (there are 2 of them), and all bridges of this triangular type design, is the bottom part of the side that spans the entire 35cm. Those pieces, when the bridge is under load, are in almost pure tension, meaning you can think about them as being pulled apart from the ends and nothing else like being bent or pushed.
Does the pattern in the side crosses matter? I see on the #001 bridge it starts being zigzag over for 3 of crosses and then switches to under for the last two zigzags. Thanks so much
I try to remember to alternate them, but it's not super critical. The reasoning to not have them all in the same direction is that those pieces get bent a tiny bit while gluing one over the other which induces a small torque to the rest of the bridge as they act like tiny springs. If you alternate, it will balance those forces out and help keep the entre bridge as square as possible
Hi its me again 😂! I was wondering what the dimensions were for each part of the bridge. For example, the bottom 2 pieces of wood, what were the dimensions of it? If you could get back to me i would really appreciate it!
It's impossible to say without seeing some pictures of your build and more details. Feel free to reach out to me at the email listed in my About tab on this channel. I did create a 6 part optimization series of videos that is all about how to optimized a design in general, so that would be a good place to start as well. Here is Part 1: th-cam.com/video/nv1ME17wME8/w-d-xo.html
I have always had a hard time stripping thin pieces of bass. Can you give any tips? Also, what thickness bass sheets are you using for the tension pieces? Thanks!!!
I have never tried stripping bass sticks from sheets. For me, it's just not worth the headache. I have recently found a nice source for them here: fnabco.com/collections/basswood-sticks For this build, I used 1/16 x 1/32 thick which should be fairly conservative at most densities. If you want to push the limit, you can try 1/32 x 1/32, but you have to be careful and choose higher density pieces and make sure they have been cut well if you want it to hold 15kg+. For the most part, I'd stick with 1/16 x 1/32. Good luck!!
Hi there, my student has been building this style of bridge. His last two bridges were 6.5 g and 5.5 g, and they held 12.5 kg and 10.5 kg respectively. None of the members broke on either of these bridges. The glue just broke loose on the top connector piece. As far as I can tell, he's using enough glue and using decent technique, although I will watch him do it next time to make sure it's absolutely correct. Is there anything else to consider to make this connection point stronger?
Hi Ryan, it's hard for me to tell exactly what is going on without seeing it. If you can send me a couple pictures to mklinger at comcast dot net, I might be able to provide some more detailed feedback. In general, the glue itself doesn't usually fail, so if his joints are popping apart, he's probably not using enough glue or pressing the pieces together long enough or both. More typically, the glue holds and it rips the balsa itself which means one of the pieces is too low a density. If you have time, have your student build a very overdesigned bridge, say 10-11g and see if that holds everything. That should really show if there are build issues. Also double check how level his build is. If it's too uneven, it will induce loads on one side that can easily rip the joint apart. Good luck!
The pieces are indeed low density, and I thought that might be an issue. On your bridge here, is the connector piece a higher density than the compression members? I might send you a picture later, thanks!
@@Ryan-qf3kz I can't remember if this bridge used exactly the same density as the legs, but it'd be very close. In general, with this design, if the top piece is the same or similar as the legs it should be balanced. While your case is low density, at 5.5g, it still should be much stronger than what I used here unless your bridge is very unbalanced between the legs and everything else. Shoot me an email and we can chat some more about it
@@balsaengineering6686 Update: He used higher density balsa on the connector pieces for his next two bridges and it worked like a dream. Got a score of 3773 at Regionals! Thanks for the pointers
Hi! What is the length of the bridge? Also, on the rules I noticed that it had a thing that said the clear span was 35 cm so I was just wondering if this bridge follows this rule. Thank you!
I'm not sure it has an official name, but in general, I like to call these just triangular bridges. They work extremely well when you have a load in the middle and the sides can be 30+ degrees.
Hi Bindu, I have been purposefully not sharing the assembly jigs for this build yet. I haven't decided one way or another if I should. Because this bridge performed so well, basically at a top National level, I'm not sure if I want to remove this challenge from the team's task. Keep checking back... if enough people ask for it I will. Thanks!
@@meeraradhakrishnan8416 Think about creating the assembly jig in 3 parts. It's probably too big to print all at once, it was for me. The middle is really just triangle with the top chopped off. Actually, you could even leave the top not chopped off and it'd work. You just need to decide exactly how wide you want your bridge to be at the bottom and top, create a triangle in a CAD program and extrude it about 45mm. The 2 end pieces are just the same width about 7-10mm tall with the same taper as your triangle from before. I made them each 180mm, but that length isn't critical. Then you need to glue the parts together. I like to use PL3 construction adhesive for that task. If you check out Part 3 of my optimization series that used the 2015 rules, at the 1:08 mark of the video you can see several examples of what I'm talking about. The 2023 version is very similar to the narrow version shown here: th-cam.com/video/0tzcp99kzdk/w-d-xo.html
Hi Bindu, enough people have asked me now, I have decided to share the jigs I used. You can download them here if you still need them! Assembly jig parts: klingerphotography.com/BalsaEngineering/2023/DivB_middle.STL klingerphotography.com/BalsaEngineering/2023/DivB_edge.STL Sides: klingerphotography.com/BalsaEngineering/2023/DivB_side_LEFT.STL klingerphotography.com/BalsaEngineering/2023/DivB_side_RIGHT.STL
I 100% agree with the beginning! My team is extremely new, and this channel has helped me and my partner heavily on how to build and to understand Science Olympiad Bridges. Thank you!
Thank you for the kind feedback! Teams like yours are exactly why I started this channel. Feel free to reach out if you have any specific questions and good luck this season!
Thank you so much! We’ve already got a head start using inspiration from this build and scored 2012. Thank you for the help!
That is a fantastic start! Keep up the great work and good luck this season!
What did the Daniel Wright MS bridge of 2015 look like? Was it a similar design? Was it shorter than the 15cm min height of this year? Did it actually hold full load or was it even lighter than 3.06g? their 4906 seems astounding and unreal.
Hi Bruce, I got your email, so I'll answer in more detail there. The short version is that I wasn't at 2015 Nationals, so I never got to see Daniel Wright's bridge. I would be shocked if it weren't shorter than what we had to do here as there was no height requirement. A 4900+ actual efficiency bridge is very, very impressive. I have only ever built one that was better and that was at much more than 15kg.
Absolutely amazing build! You inspired me and my partner so much! We think we have our final design at at weight of 3.36 scoring 6013 (assuming 15.1kgs of sand). We completely agree with you about the strategy aspect of this competition this year. Our bridge currently has a success rate of about 55% but we were looking at a design with a weight of 3.51 which works about 85% of the time. Me and my partner are still torn up about which bridge we should take to our state competition. Thank you again for your amazing deisign (it was a great starting point for us). And also we wish your team good luck in your state contest!
Thanks for the great feedback! Congrats on being able to replicate and improve on the build. Yeah, choosing the proper strategy is a critical part this year. Good luck at your state competition. BTW, I don't really have a home team anymore as my daughter is now in college. I'm rooting for everyone equally now!
Thank you! Your videos have been crucial to me and my partner, especially the density vs efficiency video! We wouldn’t be able to do it without you, we’re leaning on using the lighter design and going for it.
@@EmmettFerguson-rs9dw Thanks! I'm really glad you and your partner find my videos helpful. If your bridge is 3.36g, even if it fails early, it could still score > 4300, so not terrible by any means. It's a tough choice though. Let me know how it goes! Good luck!
@@balsaengineering6686 thanks! Well let you know on April 14th!
Me and my partner agree with you we’re going to go with the 3.36 and see how it goes.
Just wrapped up our season. Although we could not break 5900, we broke 5800. Maybe we could get there if we qualified for Nationals. We saw lots of Balsa Engineering copies.
Congratulations!! 5800 is an exceptional result! I'm looking forward to next season with Towers!
Thanks!
Hi! I'm new to build in Sci Oly and was wondering if our bridge could hang off the end of the test support? Thank you so much, this channel is already helping me immensly.
Thanks for the kind words! I'm pretty sure that would be OK, but you want to try and make your bridge smaller to just fit otherwise you are using too much material which makes it heavier without any benefit. Good luck this season!
very cool. so interesting!
Hi, First of all, Thanks you so much for creating this helpful video. Your demonstration really have made our life easier to build bridge. we made a 7.05g bridge with following your design and guideline. After putting 3kg weight it broke. Only we didn’t use the specialized balsa. Can you please help me understanding what went wrong? We are planning to make again one for state. It’s for division B.
Hi! Most likely it was an issue with your gluing technique or perhaps it not being level. It's pretty much impossible for me to help without seeing some pictures of your bridge. Feel free to reach out to: mklinger at comcast dot net and I'd be glad to take a more close look at your bridge and offer some suggestions.
Thanks a lot! We will email you shortly.
Can you shine light on the reasoning behind the tapered legs vs a square build. My son built 3 bridges of similar design to yours differing construction methods and material thicknesses slightly in each but not tapered and they’ve performed terrible. Barely holding 9000. Im assuming a jig helps hold these tapered angles true? Do you have any recommendations in jig building? Thank you for putting together a channel that is so helpful to teams. I’ve learned a lot and in turn that allows me to help my son with his builds.
Hi! The main reason to use a tapered design is for added lateral stability and less mass as the cross member pieces are much smaller as it tapers at the top. It does really help to have an assembly jig if you are attempting a tapered design or even a squared design for that matter. 3D printing is the best way. Think of it in 3 parts, the middle piece and then the 2 bottom pieces which get glued on. It would be better to print it all as a single piece, but not many printers can handle pieces that big (mine can't). If you check out the 3:05 point of this video, it shows several assembly jigs which can give you an idea on how to design and build them. th-cam.com/video/0tzcp99kzdk/w-d-xo.html If you don't have access to a 3D printer, even building something simple with wood or Lego would be better than nothing at all. Good luck!
also, dont be diss encouraged as most of my bridge team has only held 7kg - 10 kg, only me and this other guy has held 14kg-15kg
Hi! Thanks for the amazing build idea! My team is going into States soon, so I was wondering how do you cut your balsa wood?
Hi! Thanks for the positive feedback! I made an entire video on how to create a balsa library. I show a lot of cutting techniques as well. Give this a watch when you get a chance: th-cam.com/video/bLsTOpmozGI/w-d-xo.html Good luck at States!
Hi. What parts of the bridge do you recommend basswood for? Thanks.
Hi! For this build, I only recommend using basswood for the primary tension pieces.
Thanks
Hey there, how can you make it this bridge so light because 1 stick of the leg (thick light balsa) is averagely 5 grams. Also what type of wood and dimensions did you use for the legs. Thank you and nice video!
Thanks for the positive feedback! The short answer is to use lighter wood. Balsa comes in a huge range of densities. For this build, I used 3/32" thick by 8mm and each of the 4 normalized pieces I used to make the legs were 30.5 cm and they weighed around 0.8g each. Each final leg piece was about 0.61g. You might like this video I made on density vs efficiency for some more insight: th-cam.com/video/mzMFhd4SqP8/w-d-xo.html
God damn, 3.39 and over 15kg of weight???, my first bridge was unmeasured, and I put like 6 braces + 2 verticals of tension, making it weigh 6.52 g and hold 15 kg, giving it efficiency of 3067. But holy 5900 efficiency? thats almost double the standard for the bridges that had to carry moving weights.
p.s tbh, my coach told me to do 3-5 braces (not counting verticals), I think I can get my bridge designs down to 5gms and still hold the 15kg. My first bridge broke cuz my leg accidentally hit the bucket T-T ~ I know not to do that anymore-
Yep, this build was pretty insane! This is probably very close to the upper limit of what is possible. It's always nice to see what can be done to have something to compare with. Good luck with your builds, your 3067 is a very good start!
3-5 cross braces is a good suggestion. This bridge has 5, so that is obviously what I found to be the best. Vertical trussing to the tension members isn't necessary with this type of design for most leg choices. Good luck as you build more, definitely let me know how it goes!
@@balsaengineering6686 alright, thanks! good job on your videos!
Please can you share the grain that you are using for building this bridge. I have A, B and C and need help with which one is best!
This particular build used all C-grain balsa. While that might be the best possible choice, especially for the legs, it's definitely not required for great results. I have built several 4500+ actual efficiency bridges that didn't use any C-grain in previous years. Equally important is having a well balanced bridge (all legs nearly identical mass) and built as perfectly level in both directions as possible.
Hello I have a question! Our team is fairly new and we were wondering where you buy your wood and what density of balsa wood you would recommend using. Thank you! :)
I like to use Specialized Balsa for my balsa: specializedbalsa.com/products/balsa_sheets.php and Fnabco for bass: fnabco.com/collections/basswood-sticks In general, start with "Light" or "Medium" density balsa
Do you think a single laser-cut sheet of 1/16 or laminated 1/32 basswood on both sides would weigh less and support equal weight? Do you think it would be enough improvement in efficiency to warrant the trouble?
They definitely wouldn't weigh less, especially the laminated option. The glue layer adds a lot of weight. For this bridge, I was using very light, highly optimized pieces of C-grain balsa. Regarding laser cutting in general, while it'd be really fun to play around with a nice one, I don't think it would help in most cases. I see a couple big problems. If you managed to cut a side from a single sheet, first it would be really expensive as you'd be wasting most of the entire sheet. Next, the grain alignment would be totally different which might cause problems, and most importantly, the density and thus strength is not consistent throughout an entire sheet, so a side cut from a single sheet wouldn't have balanced legs. That is a big key to getting the bridge fully optimized, especially at this level of mass. Laser cutting might be very useful for smaller, more intricate pieces, like the platform pieces I'm using for the Div C design this year, but even then, it probably wouldn't justifying buying a nice $5000 CO2 laser cutter.
Hello, my daughter is a part of bridge event and i was wondering is there any specific “Glue” you use. Thanks
I like to use 50 cps CA glue. This is the exact bottle, but you definitely wouldn't want to buy that much for a single person building: www.amazon.com/gp/product/B07DK19W6M/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 I also have an entire video on glue and gluing techniques that might be interesting for your daughter to watch: th-cam.com/video/55lb2KzSiwg/w-d-xo.html
do you have a picture of how the assembly jig gets put together?
Hi! Probably the best example of seeing how this jig gets assembled is from one of my other videos where I use very similar jigs. Check out this spot in the Part 3 of my optimization video. The jig for this season is put together exactly like this. Basically just glue the 3d printed parts together. I like to use PL3 construction adhesive for that. th-cam.com/video/0tzcp99kzdk/w-d-xo.html
Hi it's me again. I noticed you have 1/20 by 1/20 bass for your cross member, where do you source the wood? I've searched fnabco, but can't seem to find them.
@@rylanchau3645 Hi! The cross members are 1/20 x 1/20 balsa, not bass. That is made by cutting sheets of 1/20" thick balsa
@@balsaengineering6686 oh, are the tension members also balsa?
@@rylanchau3645 No, the primary tension members were 1/16 x 1/32 bass
Hi! I am looking st this build and wondering at the very top what was the width from each side of the bridge. basically i was wondering what the width was at the top.😂
Hi! The inside gap at the top is exactly 1cm for this build.
What are dimensions for the little crossbar at the top?
Are you asking about the top of the side? At its widest part, it's 4.5cm
kinda late but is it fine if i use basswood for the legs and just glue two of them together?
Basswood would work fine, but you'll find that it is much heavier than balsa, so the efficiency won't be nearly as high
@@balsaengineering6686 thanks for the quick reply i just need it to be atleast 500 efficiency to pass 😅also is the height 24.6cm right? and how long are the legs
@@rk741 I would recommend drawing out your requirements on a sheet of graph paper to figure that out. That is basically what I did with this design. The Div B rules for 2022-2023 specified that the loading block height needed to be at least 15cm spanning 35cm. If you want the duplicate this design, you can download the side STL jig files linked in the description of this video as well as the assembly jig.
How would I use the stl files if I can’t 3d print
@@rk741 You could bring them into a 3d viewer and examine them to try and come up with something to use as a jig. It really helps to have some kind of assembly jig for these types of devices. If you don't have or know someone with a 3d printer, you can get them printed as a service, but I have not done that myself.
Hi I have a question! What wood did you use and what were the dimensions? The wood seems pretty thin!
The legs were 3/32" thick by 8mm and all the cross members were 1/20" x 1/20", and the primary tension members were 1/16 x 1/32" bass
@@balsaengineering6686 all bass wood? THANK YOU for making these videos! Our team last year consisted of 9 and 10-year old girls who were able to watch your videos and build some pretty amazing bridges! They walked away with medals and lots of high fives from the test proctors! I questioned giving blades and Sharpies to young kids, but they were responsible and did AMAZING... thank you!!
@@_JusticeBruv_ Hi! Thank you so much for the positive feedback! Hearing stories like yours makes all the hard work worth it and is exactly why I started this channel in the first place! Regarding this build, it's all balsa except for the primary tension members which were bass wood. Good luck this season!
Thank you!!
@@balsaengineering6686 You're a lifesaver. We made a 10 gram bridge with a similar design and we got 3rd place in regionals. When we really pushed it, it held 55kg! We're now going with the 4 gram bridge now since our team made it to state!
what type of wood was used for the side to hold the thinner pieces, bottom to hold the thicker area and what wood was used for the top part?
This bridge is all made from balsa except the primary tension members are bass wood
@@balsaengineering6686 what part of the bridge is the tension members? and what are the specific measurements?
@@indigo9971 The primary tension members are the bottom parts of the triangle sides. I would highly recommend you start with watching my Getting Started video carefully. In that video, I create an entire Div B bridge from a single sheet of balsa which can be very competitive. I go through all the details of each piece during the build: th-cam.com/video/7MwflLa5kCg/w-d-xo.html
Hi! When you assemble the jigs, is there a gap between the two triangular prices (the ones that make up one side?)
Also, what would you recommend for cutting balsa? We were using an x-acto knife and balsa cutter, but noticed while cutting perpendicular to the grain it was showing a lot of resistance, causing our wood to splinter, bend, etc.
No, there shouldn't be a gap between the triangular jig pieces, try to glue them as tightly together as possible. I like to use the miter cutter from fourmost products for most of my balsa piece cutting (not stripping from sheets, but for cutting the pieces after that). Here is a link to their product if you can get one, it helps a lot: www.fourmostproducts.com/our-products/construction-tools/ If you mean stripping the balsa sheets, one trick is to snip off the end of the x-acto blade which makes it more stuff. You can see that in my balsa library video around the 3:45 mark: th-cam.com/video/bLsTOpmozGI/w-d-xo.html
@@balsaengineering6686 Hi! Thank you so much for replying. This actually helped us construct our very first bridge today, which ended up weighing around 6.2 grams. We were wondering how to tone down the weight even further. We used epoxy glue. While stripping the balsa, we noticed that the strips tended to vary in weight quite a lot (ranging from 0.6gto 1.2g) even though they were from the same sheet of balsa. Is this normal?
Would baking help decrease this weight? What are the conditions you used for baking your bridge? Also, we used basswood for our primary tension member, so to decrease the weight would you recommend making the whole thing out of balsa?
@@avnigupta3393 Hi! Congratulations on building your first bridge! 6.2g is not bad. I would highly recommend using CA glue over epoxy. Stick with bass for your primary tension members, especially if you have 1/32x1/16 available. To answer your other questions, yes, the density variation in the sheets is normal. It's so common I made an entire video on it: th-cam.com/video/bLsTOpmozGI/w-d-xo.html and for baking the bridge, I made an entire video that goes over that and more for competition prep: th-cam.com/video/6zOvHMZLaNE/w-d-xo.html you might also benefit from my gluing video: th-cam.com/video/55lb2KzSiwg/w-d-xo.html Good luck!
@@balsaengineering6686 hi! Thanks so much for responding again. Do you know where we can acquire testing apparatus for the bridge (specifically the loading block)
Also, there is a slight bend when you glue the cross members. The top cross member causes the bottom cross member to bend. Does this affect our build? Will it affect how the build performs?
@@avnigupta3393 Hi! I know you can buy the professional testing rig here if you want: www.balsawoodhoppers.com/ It's pretty expensive and I think there is a pretty long lead time. Most teams just build something that works by putting a piece of wood between two tables and hand-loading the sand. For the loading block, just cut a 5cm x 5cm x 2cm block of wood and drill a hole in the middle. Or if you have access to a 3D printer, it's pretty trivial to print a loading block that size. Good luck!!
Hello, may I know what is considered a primary tension member in this bridge?
Hi! The primary tension members of this bridge (there are 2 of them), and all bridges of this triangular type design, is the bottom part of the side that spans the entire 35cm. Those pieces, when the bridge is under load, are in almost pure tension, meaning you can think about them as being pulled apart from the ends and nothing else like being bent or pushed.
@@balsaengineering6686 Thank you!
Does the pattern in the side crosses matter? I see on the #001 bridge it starts being zigzag over for 3 of crosses and then switches to under for the last two zigzags. Thanks so much
I try to remember to alternate them, but it's not super critical. The reasoning to not have them all in the same direction is that those pieces get bent a tiny bit while gluing one over the other which induces a small torque to the rest of the bridge as they act like tiny springs. If you alternate, it will balance those forces out and help keep the entre bridge as square as possible
Hi its me again 😂! I was wondering what the dimensions were for each part of the bridge. For example, the bottom 2 pieces of wood, what were the dimensions of it? If you could get back to me i would really appreciate it!
Also, the lateral bracing wood pieces, what dimensions were those?
Thanks!
The bottom primary tension pieces were 1/16 x 1/32 basswood for this build
The cross members were 1/20 x 1/20 balsa and the legs were 3/32 thick by 8mm. Good luck with your builds!
How do I make my bridge lighter got a score of 1700 12000 grams weight 8.65
It's impossible to say without seeing some pictures of your build and more details. Feel free to reach out to me at the email listed in my About tab on this channel. I did create a 6 part optimization series of videos that is all about how to optimized a design in general, so that would be a good place to start as well. Here is Part 1: th-cam.com/video/nv1ME17wME8/w-d-xo.html
I have always had a hard time stripping thin pieces of bass. Can you give any tips? Also, what thickness bass sheets are you using for the tension pieces? Thanks!!!
I have never tried stripping bass sticks from sheets. For me, it's just not worth the headache. I have recently found a nice source for them here: fnabco.com/collections/basswood-sticks
For this build, I used 1/16 x 1/32 thick which should be fairly conservative at most densities. If you want to push the limit, you can try 1/32 x 1/32, but you have to be careful and choose higher density pieces and make sure they have been cut well if you want it to hold 15kg+. For the most part, I'd stick with 1/16 x 1/32. Good luck!!
@@balsaengineering6686 Thank you!!
Hi! Does the bridge adhere to the pass-through block rules? Can you get it through? Is it not required this year?
Hi! There is no pass-through block this year. Definitely check out the new rules to see all the changes.
i have a question!! did you get the rules early? you said the first build of the season was on july 19th but rules only came out today.
Probably from the summer institute
Yes, this year I was fortunate enough to see the draft rules early in mid-July.
Hi there, my student has been building this style of bridge. His last two bridges were 6.5 g and 5.5 g, and they held 12.5 kg and 10.5 kg respectively. None of the members broke on either of these bridges. The glue just broke loose on the top connector piece. As far as I can tell, he's using enough glue and using decent technique, although I will watch him do it next time to make sure it's absolutely correct. Is there anything else to consider to make this connection point stronger?
Hi Ryan, it's hard for me to tell exactly what is going on without seeing it. If you can send me a couple pictures to mklinger at comcast dot net, I might be able to provide some more detailed feedback. In general, the glue itself doesn't usually fail, so if his joints are popping apart, he's probably not using enough glue or pressing the pieces together long enough or both. More typically, the glue holds and it rips the balsa itself which means one of the pieces is too low a density. If you have time, have your student build a very overdesigned bridge, say 10-11g and see if that holds everything. That should really show if there are build issues. Also double check how level his build is. If it's too uneven, it will induce loads on one side that can easily rip the joint apart. Good luck!
The pieces are indeed low density, and I thought that might be an issue. On your bridge here, is the connector piece a higher density than the compression members? I might send you a picture later, thanks!
@@Ryan-qf3kz I can't remember if this bridge used exactly the same density as the legs, but it'd be very close. In general, with this design, if the top piece is the same or similar as the legs it should be balanced. While your case is low density, at 5.5g, it still should be much stronger than what I used here unless your bridge is very unbalanced between the legs and everything else. Shoot me an email and we can chat some more about it
@@balsaengineering6686 Update: He used higher density balsa on the connector pieces for his next two bridges and it worked like a dream. Got a score of 3773 at Regionals! Thanks for the pointers
@@Ryan-qf3kz That is great news, glad to help! A 3773 score is a very well built bridge!
Hi! What is the length of the bridge? Also, on the rules I noticed that it had a thing that said the clear span was 35 cm so I was just wondering if this bridge follows this rule. Thank you!
Hi! Yes, this bridge fully followed the rules for this year. The clear span was 35 cm and the total length was about 37.5 cm
Thank you so much❤
Hello! What is the length of the legs?
At their longest point, just over 24cm
what is the name of this bridge design?
I'm not sure it has an official name, but in general, I like to call these just triangular bridges. They work extremely well when you have a load in the middle and the sides can be 30+ degrees.
Could you please share the files for the building jig that you used for this bridge?
Hi Bindu, I have been purposefully not sharing the assembly jigs for this build yet. I haven't decided one way or another if I should. Because this bridge performed so well, basically at a top National level, I'm not sure if I want to remove this challenge from the team's task. Keep checking back... if enough people ask for it I will. Thanks!
@@balsaengineering6686 Thanks!
I would also like it if you could share the files for the assembly jigs but if not I was wondering how to go about designing the jigs. Thank you!
@@meeraradhakrishnan8416 Think about creating the assembly jig in 3 parts. It's probably too big to print all at once, it was for me. The middle is really just triangle with the top chopped off. Actually, you could even leave the top not chopped off and it'd work. You just need to decide exactly how wide you want your bridge to be at the bottom and top, create a triangle in a CAD program and extrude it about 45mm. The 2 end pieces are just the same width about 7-10mm tall with the same taper as your triangle from before. I made them each 180mm, but that length isn't critical. Then you need to glue the parts together. I like to use PL3 construction adhesive for that task. If you check out Part 3 of my optimization series that used the 2015 rules, at the 1:08 mark of the video you can see several examples of what I'm talking about. The 2023 version is very similar to the narrow version shown here: th-cam.com/video/0tzcp99kzdk/w-d-xo.html
Hi Bindu, enough people have asked me now, I have decided to share the jigs I used. You can download them here if you still need them!
Assembly jig parts:
klingerphotography.com/BalsaEngineering/2023/DivB_middle.STL
klingerphotography.com/BalsaEngineering/2023/DivB_edge.STL
Sides:
klingerphotography.com/BalsaEngineering/2023/DivB_side_LEFT.STL
klingerphotography.com/BalsaEngineering/2023/DivB_side_RIGHT.STL
12000