What makes you think the bearings are failing due to axial load rather than radial? I think their resonse to different weapon hits doesn't tell the full story. From the geometry (two closely spaced bearings in a large diameter weapon), I'd guess that when your weapon initiates an impact, the bearings will roughly share the load, so each bearing will see about half the impact force. Its probably worse than that, because they're not on the centre line, but its roughly the case. When the blade gets hit by a vertical spinner, maybe each bearing will see half that axial load. But they'll also see a radial load of about 10x the impact force. That's because the bearings need to resist both the blade bending and the axial force. Since the bearing spacing is on the order of 10mm and the weapon radius is on the order of 100mm, there's a 10:1 leverage going on. So the majority of the load is probably still radial; I'd expect them to fail by radial overload. If your specific bearings are 1/10th as strong axially as radially, you may be correct about the failure mode, but I think the axial:radial strength of deep groove ball bearings is typically ~1:2. If my above assessment is true, your proposed solution may still be the only option, but doing what you can to seperate the bearings may yield bigger gains. Like a thin section bearing below the magnet ring, and a single typical section bearing above? I'm sure you can think of other ways to package something like that within your height constraints, though I'm not sure if they would be within weight.
I think you're right, and I've given this a LOT of thought, but I keep coming back to the same thing. I'll try it this way, and if that doesn't work, I might go a different route.
Angular contact for the win and make it as large as you can also reduce weight on weapon by drilling holes. It does plenty of damage already. Reducing centrifigul mass would reduce stress on the bearing as well and keep you from having to replace them so often
One simple solution to small bearings in small spaces is to split the bearing into a basic setup, kinda like bicycle hub bearings. Top part holds the upper race, bottom part, bottom race, and the balls ride in a cage. That way you don't have to deal with encasing bearings into parts, you can have them be part of the design. Plus, you only need this to last a few fights, not eons, so as long as the races meet spec, you could have a very small bearings, take a lot of abuse. I mean, think about it, BMX cage bearings take up a metric frakkton of abuse and they're what ... less than 10 balls. I've seen jumps that have dented the rims to the point where they touched the hub, and the kid would just swap the rim and spokes and reuse the hub (since it almost always was, the most expensive part). That's a stout system if you ask me. Just a thought. Also, once a setup like this is tightened right, you can take out almost all the slop in the mechanism, if not all, since you're not relying on pre-manufactured bearings to hold the tolerances you need, you're the manufacturer, and assembler. It also takes out a lot of complexity. From a bearing with all its components to a frame bearing and balls. Will say this tho, if you need to swap them, put a towel under...lost balls are not fun.
..this got me thinking of a new constraint for Mr. Cowan - spoke suspended weapon robot! Might reduce the bearing peak load load - and add some weight gain. Also there is the option for dyneema(?) spokes 🤓🤔
I think you’ve prematurely discarded tapered or offset bearing candidates. Just increasing the size of deep groove bearings isn’t really correcting the problem which is that they are not designed with those loads in mind. You already know this, and you will be kicking yourself when this inevitably fails again.
Your recessed pieces still need to be mounted. Are you going to add beefier plates for that or do you have faith that the thinner frame will be strong enough to bolt it all together?
The 6mm carbon fiber has been MORE than strong enough. I will be pocketing 3mm into each plate, which will still leave a good amount of thickness. I think this should be fine. Even Billy didn't do that much damage to the frame, just some chips here and there. Also, the frames are surprisingly cheap.
How did you remove the stator from the base? I've been wanting to do that with one of my motors but I'm a bit afraid of damaging the stator while doing so. Did it have any type of glue/epoxy holding it together?
Uhm sorry if that comment is dumb, but what happened to Psychotic Break? It didn't look like that after the last damage recap and I can't find any video about a recent competition on your channel? O.o
@@RobertCowanDIY ahh okay, I was really confused, because usually I try to keep up with your content as good as I can. Was the weapon also grinded down on one site too? Or was that a measure to clean up rough and sharp edges from last competition?
Bushings also don't 'hold' things in place. They are for rotating parts, but they allow things to flop all around, which I can't have with this design.
Everything is a compromise! But yes, it will be slightly thinner around the weapon mount, but only a 3mm deep ~26mm wide pocket. It's 6mm thick, whereas most people do 2-4mm max. should be fine.
Anyone else realize that in another 10 or 20 years we're going to have all these super smart mad scientist guys with big grey beards :D I'm only 37 and don't have a beard but I want to go that route once I go all grey. Kind of like Rick on Rick n Morty, but I'm bald so I have to have a beard instead of the crazy hair.
Some smal thrust bearings or bushings just for axial load is no option? I gues even for those biger ball bearings the axial shocks are quite dangerous.
@@RobertCowanDIY I just meant additional trust washers between frame and rotor and let the bearings float a little bit on the shaft instead of clamping the whole rotating assembly axial true the ball bearings.
have you looked at the UK BW Daedelus ? that hub motor compact and I cannot remember one time it failing, facebook.com/BadTimingRobotics/photos/2190970780996832
10:35 I'm not mature enough for this conversation.
Ayyyyy more combat robots
What makes you think the bearings are failing due to axial load rather than radial? I think their resonse to different weapon hits doesn't tell the full story.
From the geometry (two closely spaced bearings in a large diameter weapon), I'd guess that when your weapon initiates an impact, the bearings will roughly share the load, so each bearing will see about half the impact force. Its probably worse than that, because they're not on the centre line, but its roughly the case.
When the blade gets hit by a vertical spinner, maybe each bearing will see half that axial load. But they'll also see a radial load of about 10x the impact force. That's because the bearings need to resist both the blade bending and the axial force. Since the bearing spacing is on the order of 10mm and the weapon radius is on the order of 100mm, there's a 10:1 leverage going on. So the majority of the load is probably still radial; I'd expect them to fail by radial overload. If your specific bearings are 1/10th as strong axially as radially, you may be correct about the failure mode, but I think the axial:radial strength of deep groove ball bearings is typically ~1:2.
If my above assessment is true, your proposed solution may still be the only option, but doing what you can to seperate the bearings may yield bigger gains. Like a thin section bearing below the magnet ring, and a single typical section bearing above? I'm sure you can think of other ways to package something like that within your height constraints, though I'm not sure if they would be within weight.
I think you're right, and I've given this a LOT of thought, but I keep coming back to the same thing. I'll try it this way, and if that doesn't work, I might go a different route.
If you design something great ⚙️ people will always fill the arena seats. Looking forward to your next upgrade video!
Hub motor is best motor
Fo sho.
True story
Angular contact for the win and make it as large as you can also reduce weight on weapon by drilling holes. It does plenty of damage already. Reducing centrifigul mass would reduce stress on the bearing as well and keep you from having to replace them so often
Love the combat robot videos
He said "larger balls"... Yes I'm "that" guy :)
One simple solution to small bearings in small spaces is to split the bearing into a basic setup, kinda like bicycle hub bearings. Top part holds the upper race, bottom part, bottom race, and the balls ride in a cage. That way you don't have to deal with encasing bearings into parts, you can have them be part of the design.
Plus, you only need this to last a few fights, not eons, so as long as the races meet spec, you could have a very small bearings, take a lot of abuse. I mean, think about it, BMX cage bearings take up a metric frakkton of abuse and they're what ... less than 10 balls. I've seen jumps that have dented the rims to the point where they touched the hub, and the kid would just swap the rim and spokes and reuse the hub (since it almost always was, the most expensive part). That's a stout system if you ask me.
Just a thought. Also, once a setup like this is tightened right, you can take out almost all the slop in the mechanism, if not all, since you're not relying on pre-manufactured bearings to hold the tolerances you need, you're the manufacturer, and assembler. It also takes out a lot of complexity. From a bearing with all its components to a frame bearing and balls.
Will say this tho, if you need to swap them, put a towel under...lost balls are not fun.
Do you have a picture, I'm not visualizing what you're talking about.
..this got me thinking of a new constraint for Mr. Cowan - spoke suspended weapon robot! Might reduce the bearing peak load load - and add some weight gain. Also there is the option for dyneema(?) spokes 🤓🤔
I think you’ve prematurely discarded tapered or offset bearing candidates. Just increasing the size of deep groove bearings isn’t really correcting the problem which is that they are not designed with those loads in mind. You already know this, and you will be kicking yourself when this inevitably fails again.
I did some more looking and I think I might be able to fit some angular contact bearings in there, which would help tremendously.
@@RobertCowanDIY Thank you. I've been stewing over this all day, LOL. I'm rooting for you so hard!
I'd pocket into the weapon, prioritizing size of pocket over depth.
Yep, that's exactly what I'm thinking too.
@@RobertCowanDIY or heavy chamfer around the edge of the weapon. I'm not sure which would be best...
Thank you for content
Would the design for Psychotic Break work well for a heavyweight bot?
Check out Malice from last season. Malice was partially inspired by PB.
It seems like tapered bearings would be the way to go on the main weapon.
Your recessed pieces still need to be mounted. Are you going to add beefier plates for that or do you have faith that the thinner frame will be strong enough to bolt it all together?
The 6mm carbon fiber has been MORE than strong enough. I will be pocketing 3mm into each plate, which will still leave a good amount of thickness. I think this should be fine. Even Billy didn't do that much damage to the frame, just some chips here and there. Also, the frames are surprisingly cheap.
How did you remove the stator from the base? I've been wanting to do that with one of my motors but I'm a bit afraid of damaging the stator while doing so. Did it have any type of glue/epoxy holding it together?
I have a short video coming up, I made a little 3d printed jig and arbor press. Worked great.
Uhm sorry if that comment is dumb, but what happened to Psychotic Break?
It didn't look like that after the last damage recap and I can't find any video about a recent competition on your channel? O.o
Oh, it was just taken apart from the last damage recap, you didn't miss anything.
@@RobertCowanDIY ahh okay, I was really confused, because usually I try to keep up with your content as good as I can.
Was the weapon also grinded down on one site too? Or was that a measure to clean up rough and sharp edges from last competition?
Why not use bushings? What are the disadvantages?
Well, in a high rpm application bushings are not ideal. Bearings will offer less friction and less heat build up.
Bushings also don't 'hold' things in place. They are for rotating parts, but they allow things to flop all around, which I can't have with this design.
Compromising on frame strength?
Everything is a compromise! But yes, it will be slightly thinner around the weapon mount, but only a 3mm deep ~26mm wide pocket. It's 6mm thick, whereas most people do 2-4mm max. should be fine.
Anyone else realize that in another 10 or 20 years we're going to have all these super smart mad scientist guys with big grey beards :D I'm only 37 and don't have a beard but I want to go that route once I go all grey. Kind of like Rick on Rick n Morty, but I'm bald so I have to have a beard instead of the crazy hair.
Some smal thrust bearings or bushings just for axial load is no option?
I gues even for those biger ball bearings the axial shocks are quite dangerous.
Yep, but with a hub motor, any radial play (from bushings) will cause the magnets to rub against the stators.
@@RobertCowanDIY I just meant additional trust washers between frame and rotor and let the bearings float a little bit on the shaft instead of clamping the whole rotating assembly axial true the ball bearings.
@@martin09091989 Gotcha. I might have to think about that, but I don't think I'd have the room. I wish I could find a smaller angular contact bearing.
Psychotic Break vs Copperhead
have you looked at the UK BW Daedelus ? that hub motor compact and I cannot remember one time it failing, facebook.com/BadTimingRobotics/photos/2190970780996832
Yep, I have! He holds everything a bit differently. I'll see if these changes improve anything, but I might look at that next.