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Quote:

Originally Posted by Lil Giants (Post 30707)

35rpm sounds plenty quick for the gh motors' rpm -> what's the diameter of the tire?

What's the wall thickness of the tube to tap threads for the set screws? You gonna drill into the gearhead a bit too?

Hi Joe,

I am using the RC4WD Mil-Spec ZXL 2.2 tires. The diameter is 5.17" (131mm).

I am going to use some M5 set screws and I do plan to drill slightly into the gearhead casing. The tubing is approx 2.43 mm thick where I will drill through (just past where it steps up on the outside). The motors fit in the tubing without any slop so the set screws are to hold it in place and stop the motors from rotating or coming out. I also plan to use some liquid gasket seal, something that isn't permanent but that will give it some friction to help stop the motor from turning in the tubing.

Richard

So, I did a bit of research now ;)

First I found: I couldn't find a "Cat 350D" ADT, but there is a John Deere 350D.
http://www.deere.com/wps/dcom/en_US/...series_ii.page

EDIT: Okay, the truck is a Cat D350 or maybe a D350D...
Anyway, both use 26.5R25 tires:
http://www.bridgestone.eu/upload/album/AP_429.pdf

These have an outer diameter of 1736mm.
http://www.bridgestone.eu/upload/album/AP_429.pdf
The RC4WD tires have a diameter of 131mm.
->Scale 1736/131 = 1:13.2

The circumference of the original tire is 5.45m
This means that from the John Deere pdf (I didn't find a D350D one but from http://www.ritchiespecs.com/specific...&modelid=91901 we can guess that the D350D as a speed like the Volvo 350D without its 6th gear) we can convert their speeds to rpm at the wheel:
1st gear = 25rpm (5 mph)
2nd gear = 52rpm (11 mph)
3rd gear = 74rpm (15 mph)
4th gear = 113rpm (23 mph)
5th gear = 144rpm (30 mph)
(6th gear = 165rpm (34 mph) only John Deere)

If you intend to do only (very) short hauls, 35rpm seems maybe acceptable, if the 35rpm of these motors is the load speed. If it's the no-load speed, I think that even then it would be too slow.

Cheers
Jens

Wow, that's a lot of work Jens! Yes, it is a D350D not a 350D. If it is too slow, I will change out the motors (which might require re-tubing the axle housing) or perhaps try to make a reverse planetary. Realistically though, I think I will be happy if it ever moves under its own power in my kids' sandbox (which happens to be 14'x24').

Richard

Hi Richard!

That's a big sandbox! Would love to have one that size to play in =)
But I agree, for that size, a slow but torquey motor is maybe not such a bad idea.
And as I said, you could always mount some motors to a wooden plate and see how it goes in the sandbox :)

Cheers
Jens