Crazy axles idea design

[12earth]

Originally Posted by gonper

Most of the looses of that torque are on the worm gears that have lots of friction.

Fascinated by this project. I am not an engineer nor do I know if you can scale it down but, have you seen the Cyclo transmissions.

https://m.youtube.com/watch?v=dYVPU47c9WA



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[CM9000]

Originally Posted by TheLetterJ

Maybe 380 sized outrunners could be packaged better and avoid the need for sensors?

I might have been wrong, 280 size. found here...

Losi: 1/18 Xcelorin Sensored ESC/Motor Combo: MRC: Losi (LOSB9567)

and maybe with a re design to accommodate the bolt patern and flipping the shaft you could go with something like this.

https://www.amazon.com/LHI-920KV-Bru...ss+motor&psc=1

might be to big though.

[Gandalf The White]

Originally Posted by CM9000

I might have been wrong, 280 size. found here...

Losi: 1/18 Xcelorin Sensored ESC/Motor Combo: MRC: Losi (LOSB9567)

The problem with that is the rpm, it claims free speed upward of 20,000 rpm, at only 7.2v. http://www.losi.com/ProdInfo/Files/LOSB9464_Manual.pdf
At only 30:1 reduction thats pushing 700 rpm on the wheels... say a 7in diameter wheel * pi * 700rpm = 15,000 ipm or about 20fps/13mph. Thats pretty fast for a crawler, and was only at 20k rpm... it could be closer to 30k rpm on lipo voltage.

[Gandalf The White]

Originally Posted by CM9000

Maybe with a re design to accommodate the bolt patern and flipping the shaft you could go with something like this.

https://www.amazon.com/LHI-920KV-Bru...ss+motor&psc=1

might be to big though.

Those say they are 2212, 22mm diam. 12mm tall (on the stator, I think). If gonper has 380 size motors fitting now, which are about 28mm diam. those motors are actually too small (probably). But you are correct, something like that would be my recommendation. 920kv on 3s is only 11,500 rpm, so a much more reasonable range. A slightly larger motor with lower kv (like 750 or something) would be what I would look for.

[gonper]

My first idea was to use brushless motors but as you say it is difficult to find sensored ones with the right size and speed (KV) and sometimes they are overpriced as well... That is why I decided to go brushed way.

About brushed motors that I have to test:

- JRS-385RA/SA: 8500rpm at 7.4V (This one was too slow and low power, so not suitable)
- Mabuchi RS380PH-3270: 10000rpm at 7.4V (Speed of this one is OK but limited power, with lower friction may be a good candidate)
- SRC-380SA-3065-55: 13000rpm at 7.4V (Waiting to receive it and test...)

And there is easy to find higher KV ones but that will require changing the gear ratio, that will mean as well to redesign the gearbox, not a big drama, just some hours on the CAD drawing and printer.

I already have found different worm gears suitable for that modification that can allow use higher revs. motors:
1:60 worm gears
1:50 worm gears

[gonper]

Thank you for all the inputs.

Fascinated by this project. I am not an engineer nor do I know if you can scale it down but, have you seen the Cyclo transmissions.

https://m.youtube.com/watch?v=dYVPU47c9WA

That is great but that kind of gearboxes are used for CNC positioning and other precision staff that actually its not need in this case.

I might have been wrong, 280 size. found here...

Losi: 1/18 Xcelorin Sensored ESC/Motor Combo: MRC: Losi (LOSB9567)

and maybe with a re design to accommodate the bolt patern and flipping the shaft you could go with something like this.

https://www.amazon.com/LHI-920KV-Bru...ss+motor&psc=1

might be to big though.

Both are a bit too small and sensored is a must, else the motor starts with almost no torque.

[gonper]

One question:

What is the top speed of a crawler this kind?
Have anyone checked that?
I was guessing around 10 to 12Km/h (6-7.5mph), am I right?

[Gandalf The White]

Originally Posted by gonper

One question:

What is the top speed of a crawler this kind?
Have anyone checked that?
I was guessing around 10 to 12Km/h (6-7.5mph), am I right?

That's about the max I would want, yes... generally speaking.

Originally Posted by gonper

My first idea was to use brushless motors but as you say it is difficult to find sensored ones with the right size and speed (KV) and sometimes they are overpriced as well... That is why I decided to go brushed way.

About brushed motors that I have to test:

- JRS-385RA/SA: 8500rpm at 7.4V (This one was too slow and low power, so not suitable)
- Mabuchi RS380PH-3270: 10000rpm at 7.4V (Speed of this one is OK but limited power, with lower friction may be a good candidate)
- SRC-380SA-3065-55: 13000rpm at 7.4V (Waiting to receive it and test...)

And there is easy to find higher KV ones but that will require changing the gear ratio, that will mean as well to redesign the gearbox, not a big drama, just some hours on the CAD drawing and printer.

I already have found different worm gears suitable for that modification that can allow use higher revs. motors:
1:60 worm gears
1:50 worm gears

So that middle motor (Mabuchi), is it a 3270 can size (32mm diam 70mm long)? If so, can you squeeze an extra 3-4mm on the diam? Because normal (read: readily available) 10th scale motors are 3650-3665, and have plenty of sensored options, as well as brushed options with a lot of power.
45t 540 Brushed
Sensored Brushless

[gonper]

Originally Posted by Gandalf The White

So that middle motor (Mabuchi), is it a 3270 can size (32mm diam 70mm long)? If so, can you squeeze an extra 3-4mm on the diam? Because normal (read: readily available) 10th scale motors are 3650-3665, and have plenty of sensored options, as well as brushed options with a lot of power.

All are same 380 size (38mm length 28mm diameter) the other numbers/letters relate to the windings and other characteristics, each manufacturer has different reference numbers...
I doubt that it will be possible to fit a 540 size motor this way...

[gonper]

BTW, I managed to cut and shut the tires.
This is my first time I cut and shut tires so I decided to use the cheap tires I found on Alibaba that will allow me to learn how to do so and test the rig.
I am very happy with the results.
Then latter will make comp ones with other kind of tires.

[Gandalf The White]

Originally Posted by gonper

All are same 380 size (38mm length 28mm diameter) the other numbers/letters relate to the windings and other characteristics, each manufacturer has different reference numbers...
I doubt that it will be possible to fit a 540 size motor this way...

Hmmm, OK.

That wheel looks great, too.

[gonper]

All parts printed.
Now need to make the suspension and steering links.
And wait for the motors to arrive

[CM9000]

does that say "version" 5? in the one case?

also, lets get a sneak peak at that chassis!

sorry if I was no help with finding motors. I thought for sure leopard rc had a 380 sensored motor. but when I was on their site, I could not locate one.

[gonper]

Originally Posted by CM9000

does that say "version" 5? in the one case?

also, lets get a sneak peak at that chassis!

sorry if I was no help with finding motors. I thought for sure leopard rc had a 380 sensored motor. but when I was on their site, I could not locate one.

Yes, it is printed iteration number 5, it is very difficult to get the tolerances correct with 3D printing when a precision of around 0.2mm is need...

Thank you for your search, I am going to keep with the brushed option for now, I have a couple of ideas in order to make it work well.

[gonper]

Et voila

Steering and suspension links.

[Gandalf The White]

Wow, those look really, really sweet. So close to a full assembly.

[gonper]

And here we go, first assembly.
Please let me know your thoughts.
It looks like everything goes together quite well.
May need to order some more screws sizes as some are short some others are long, and add some washers/seams here and there, not a big deal

And wait for the motors to arrive that I hope they come next week.

[Gandalf The White]

Amazing!!! What is you plan for battery placement/size? Are they in the wheel assemblies?

[CM9000]

wow... that's probably going to be one of the lightest supers on the planet.

I bet.. as it sits in the last picture it doesn't weigh more than 1.5 lb.

[gonper]

Originally Posted by Gandalf The White

Amazing!!! What is you plan for battery placement/size? Are they in the wheel assemblies?

2 batteries 7.4V (2S) 800-900mAh
One on each front wheel.
Everything is inside of the wheels: motor, gears, battery, servo, ESC. Only receiver is outside.