RedAsh

Hi guys, I have had an electric rc car for a few years and now I want to make a petrol on road rc car, I have a 30cc motor a radio, receiver and throttle servo but I need a steering servo I was thinking about getting the savox 40kg mega torque high voltage servo are they any good?
I was also going to have a live axil with just a sprocket on it being driven buy a chain going from the sprocket on the motor, I wasn't going to make any suspension or a diff, what do you think?

Lars from Norway

I replied in your thread on another forum, but i was going to direct you to this one as there is far more homebuilding going on here.

You say you are going to have a live axle, but how can it be live when it is not any suspension on it? I see how you are going to setup the sprocket and chain, but what i promise you is that you must have a gearing on about 6:1 or maybe higher on a engine like this, which means you might end up with a sprocket on the rear axle that is bigger than the wheels. Have you got any plans for what wheels to use? Have a look at the pinned thread on top of this forum, many builds there where you can get some ideas.

RedAsh

I am going to have a pillow block bearings on the underside with a half inch axil running through the middle and a sprocket mounted to that, meaning the axil will turn, isn't this a live axil? I hadn't thought that I would need such a reduction, I might have to use a belt drive system to make it work. As for the wheels I haven't decided yet, I don't want to spend to much on them so I was thinking about using trolley casters or turning some wheel hubs out of wood and using bicycle tire intrude for the rubber, a little jery-rigged but it should work, I will look at the thread and see what ppl have got.
Thanks for the help

Lars from Norway

Yeah, you wouldn't want a non-turning axle, eh? I think Dirty Vinylpusher has one or several cars with the same axle setup as you mention here, if i understand you right now. Would be funny to see some wooden wheels on a large scale car, hehe! Hope to see some pics of how it turns out.

Dirty_Vinylpusher

Dual axle and sprocket setup?

http://www.rcuniverse.com/forum/rc-g...l#post11739987

(Link should take you to post #14)

Works well.
A minimum reduction of 6:1 is usually good.

RedAsh

I found some wheels, went down to the dump shop and picked some up but I may still experiment later, I also got another motor, turns out the one I had didn't have a sentrafugal clutch if I can get the new motor to work I should have a chasi made up tommorow.
Btw i was thinking to get a bigger ruduction i would us a jackshaft good or no?

Dirty_Vinylpusher

Yes.
See link in the post above....

RedAsh

Haha, that's almost exactly what I had in mined.

Dirty_Vinylpusher

http://www.rcuniverse.com/forum/rc-giant-scale-cars-234/10037255-gear-ratios.html#post10037255




http://www.dynamicscience.com.au/tes...s1compound.htm

RedAsh

Thanks Dirty_Vinylpusher. I herd that there is a way you can convert motors into servoes does anyone know anything about that?

Lars from Norway

Read about it here: http://www.rcuniverse.com/forum/rc-g...er-servos.html

Dirty_Vinylpusher

Also, Perreault just built one.

Perreault985

I did just finish building one of these and it works quite well. It was based it on the information provided in this Popular Science article http://www.popsci.com/diy/article/20...ject-you-build. I upgraded to the 30A pololu JRK12V12 motor controller since I knew wiper motors could draw quite a bit more ampage. I'm not sure the 3A would have been enough and didn't want to find out the hard way. I haven't put an amp meter on mine yet, but did trip the load limit setting one time when the wheel was wedged in to a corner on my work-bench.

The instructions with the controller were a little difficult to follow at first, but once I read through them a few times it made more sense. Take a look at the video on their site and check out the wiring. Just attach a female RC connector to the first thee pins and then route it to your reciever. The power IN and OUT circuts are clearly marked on the other side of the board. You will need a good soldering iron since none of the pins are soldered on this model. If you have not soldered on small circut boards before, ask a friend for some help who has some experience.

The last thing I'd reccomend is connecting the potentiometer shaft directly to the wiper motor shaft . I tried the linkage as a lot of people did, but kept getting into a feedback loop because of slop in the linkage. I have a few pictures on the thread I'd started, http://www.rcuniverse.com/forum/rc-g...ilt-buggy.html
Let me know if you have any questions.

RedAsh

Thanks for all the help guys, I have the frame done and will be moving on to the motor mount and jackshaft soon, in the meantime here are some pics.

I can't take all the credit, my helper kept up morel support, I think it bores him to death though


Ps, thanks Perreault985 for the info.

Dirty_Vinylpusher

That's a good start.
You'll need some diagonal bracing though to stop the whole thing twisting and folding up like garden chair.
Or put a few welds on each corner.

And that's a fine looking dog by the way

RedAsh

Thanks, I was planing on running a pice of RHS up through the middle as a backbone sort of thing, that will also support the motor mount. Also I was planing on using a universal joint to allow for any vibrations, not to mention the fact that I will make my own centrifugal clutch housing so that won't be 100% accurate but in all I think it should work.

Lars from Norway

Looks nice (and here comes the "but") but where the frame narrows in to the front might be a weak point as it is only one crossmember there and not two. If the frame gets the idea to bend and sag, it will be here. A plate will do the trick to stiffen it up so it don't end up as a romb shaped thing, but that is maybe where you are going to attach the engine?

RedAsh

Okay guys, I have been away and am still going to be away for another few days but I was up at my grandfathers shed and he gave me a 40:1 right angle reduction box so instead of a jackshaft I will use this and have a 1:4-5 increase going from the shaft to the axil, I will get it mounted soon but I have a heap of homework to catch up on and I still have a really busy week ahead but I will have an update soon I hope. btw I am going to fix the hole bending problem when I get the time.

Dirty_Vinylpusher

40:1 ?!?!?!?!

How big is this thing?
Must be huge if it's only got 2 gears in in.
Or are there more than 2?

What's it from?

RedAsh

It uses a worm drive, it is a little bigger that I would like but it will be smaller than a jackshaft.