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- เผยแพร่เมื่อ 15 ก.ย. 2024
- An interesting project but a bit of a dead end at the moment. The motor gets way too hot too quickly to be practical.
I got the idea from old topics on RC forums, mostly back from around 2005-2007.
For a brief time, there was a small trend for taking a large brushless outrunner motor and fitting it in place of the transmission on 4wd trucks, the gearbox was removed completely and a drive shaft went from each end of the motor directly into the diffs.
It's a bit pointless these days because decent inrunner motors are cheap and easy to obtain in all sorts of shapes and sizes but back then, large and powerful inrunner motors were scare and very expensive so a larger, slow outrunner mounted directly to the diffs was a way to get big brushless power without selling internal organs and as a bonus you had less gears to worry about breaking.
Skip forward to 2020 and the idea of doing this kind of mod is absolutely pointless apart from it being interesting and different.
I decided to try it with my HSP Brontosaurus simply because it's a shaft driven 4wd truck and it's cheap and easy to buy spares including an alloy chassis for £6!
The motor is a DYS 3548 900KV. It worked ok on 2s except a little cogging and the top speed wasn't great. On 3s the cogging is almost gone and the top speed much better but the temps are just ridiculous. After just what you see in this video, the motor was hot enough that I could smell it before I even touched it. Imagine if I had been driving on grass or sand etc. Simply not practical for everyday use.
Unfortunately, it seems like there isn't really a sweet spot for this method using 3s on this truck. A larger motor would run cooler but I can't find any with the same KV rating so it would have to be slower too meaning I could have to go up to at least 4s and probably 5s which is a lot to squeeze in to a relatively small chassis. I would also be worried about the diffs blowing because this motor is already pretty brutal when you dump the throttle from a rolling start.
So all in all, it was a fun experiment but the size and speed of the motor just cannot deliver the goods and stay cool enough. It's a shame because I love the way it performs. You would never know the motor was getting so hot from the way it performs because it feels like it's effortless. It just glides around with hardly any throttle and then when you pull the trigger it just takes off on a huge wave of torque.
For now, the truck will be going back to stock configuration with the gearbox and inrunner. I can't justify buying various outrunner motors, trying to find one that works and I'm not buying a 5s capable ESC just for a curiosity project.
I will try different timing and a different ESC first just in case there was something going on there causing the heat but I'm pretty sure the motor is simply not quite suitable.
I will keep an eye out for cheap motors on ebay, you often see second hand ones that came out of planes going for quite cheap so there's still hope. I haven't given up on the project but I will wait for the right kind of motor to come my way cheap.
I hope you enjoy the video even though it could be described as a successful failure.
What a Beast 😍
The reprises/recovers in low medium speed are Astonishing 👌😎
And the noise...dude, i even put my phones to ear it 😁 it's a tsunami.
One of the fastest acceleration RC i ever seen 👌👌👌👌👌
I don't think it was a fail... i think still is a "running project"... i hope 😁
Can't get tired of seeing the Video 😍
That thing is quick off the line!
I love how it performs, it's a shame the motor gets so hot. Just a tiny bit too small I think. It has the power but not the thermal capacity!
very cool project I am sure you know outrunners have very little torque they are most high rpm motors that's why drones and such like use them you would be better using a 4pole motor they pretty cheap too these days
Outrunners generally have more torque for their size. That's why they are used in electric cars and bikes etc.
This particular motor has 14 poles and is 900KV
Drone and helicopter motors tend to be higher KV but they are still have considerable strength vs an inrunner of the same size. They are used in flying vehicles because they can produce the same power from less mass.
My Lunchbox has a tiny 4400KV inrunner about the same size as a 280 motor but it performs similarly to a 540 inrunner.
@@ValleyRC yes i have seen your lunchbox video awsome i do have one rc that has these outrunners looks kinda like a drone motor i stand corrected always thought they had no guts
@@steveclough6794 it generally depends on the size like any motor but if you have an outrunner and inrunner the same size and RPM then the outrunner will tend to have more torque because it has more poles and a bigger rotating mass because the outside spins vs the inside.
High RPM outrunners tend to be physically smaller though because the advantage is used to make a smaller and lighter motor with similar power instead of making a motor the same size but with greater power.
Little drone motors are still pretty weedy but that's because of their size. If you had an inrunner the same size it would be even more weedy generally.
The idea of this project was to bypass the pinion/spur gear and send power directly to the front and rear diffs. I did originally try a 3670 1000KV 4 pole inrunner connected to just the rear diff (you can't have the shaft coming out both ends of the motor like you can with an outrunner) but it couldn't get off the line, just cogged and stuttered. The 900KV outrunner copes much better but still not quite there.
As it was only a fun project, I don't want to spend money trying out motors till I find a suitable one so for now, I have gone back to the trusty 3300kv 4 pole and the original transmission which works just fine.
It definitely makes more sense to just use a 4 pole and transmission but this was just a fun project.
@@ValleyRC thanks for your detailed information they do say you learn something everyday and i have most definitely learnt today subscribed and look forward to your next video
Nice.
Thank you! Cheers!