Low RPM, high torque for rc car

[barnesrickw]

I'm looking for plans for a low RPM engine that has high Torque for an RC car. Not interested in going fast, but want a more scale sound than something screaming along at 15k-25k rpm. I was thinking of a diesel with a long stroke. Are their plans that exist?

 

[Blogwitch]

Four stroke engine with at least a couple of cylinders would be much better than a two stroke diesel, only half the number of 'beats' if you go for a single, but much better sounding anyway.

John

 

[Herbiev]

http://www.homemodelenginemachinist.com/showthread.php?t=14558
Great engine here. 520 rpm idle.

 

[mu38&Bg#]

The reason the 1/8 or 1/10th scale car engines run that fast is to make power. Getting more torque from a little engine like that is near impossible, so low RPM means less power. OS made a FS-26S-C and FS-40S-C for a while, but even these ran up to 22kRPM and 17kRPM respectively. This is something I've thought about. The best you could hope for is maybe a two cylinder four stroke. There is the Tiny. http://www.homemodelenginemachinist.com/showthread.php?t=14833 Power is very low, but it might work. Durability compared to even the cheapest of hobby engines will be miserable unless you can harden or use hard components where needed. If you're talking 1/5th, or 1/4 scale, things seem much more practical.

Greg

 

[barnesrickw]

I'm more interested in scale operation than speed. 3,000 rpm would be fine with me. I can turn and mill drill rod with little problem. Just kicking around ideas in my head. Would love to do a scale model-t. But again, cam shafts seem out of my limit.

 

[mu38&Bg#]

Don't let that stop you. I'm always amazed at how well certain aspects of tough projects turn out for me. Start with the cam, once you figure it out the rest will be easy.

 

[Cogsy]

I agree, have a go at it. There is a great tutorial by Steve Huck on turning cam shafts on the lathe (needs an easily made jig). First go I turned out my V4 cam with no problems at all. Far easier than I thought it would be.

 

[GailInNM]

Size matters. If you're thinking of fairly small model you may be limited to a single cylinder engine. Assuming that the engine will be concealed then you have a lot of freedom as to design.

To give you a few ideas, here are some links to some of the small 3/8 inch bore by half inch stroke engines that I have used two power Gauge one locomotives. These locomotives are all about 12 inches long. I have built 10 of them and all run fine at a scale 15 miles an hour. Power does not seem to be a problem as I have pulled over 20 cars at once. Beyond that wheel slippage was a problem.

I use cast-iron cylinders with lapped pistons and have over 1000 hours on one of the engines. The conrod big end is pretty sloppy but no other real problems with wear. All of the engines used in locomotives have been hit or miss versions with the governor set at 3000 RPM. This gives a very realistic sound to this type of locomotive. I built a carbureted version but it was pretty finicky and did not like the idle below about 1500 RPM.

Here are some video links including a link to my YouTube channel which has a lot of engines of similar design running on test stands.

Gail in NM

https://youtu.be/xXnWSJOSuE0
https://youtu.be/a-csJ3As7dc
https://www.youtube.com/user/nmsteam/videos

 

[barnesrickw]

Thanks everybody for the encouragement. Maybe I'll start with the cams. If they work out, try the rest of the engine. The videos were amazing. Where is that track located? Club track, or your track?

 

[GailInNM]

Thanks for the comments on the videos. All of the videos were shot on private tracks. Most of them were taken in Utah (USA) at a mountain track about 40 miles west of Salt Lake City. The once around the track video was taken up in British Columbia ( Canada).

Keep us posted on what you decide to do. No matter what approach you decide to go with we are always interested.

Gail in NM