Transmission question

[Section8]

Hello,

I am starting a sort of crawler project. Its more of a scale project than a performance crawler, but since I am interested in makeing it as capable as possible within the scale apperance I will be posting questions about it as I go along.

My first problem is the transmission.

THis is a simplified tranmission showing just the gears and their interaction (shafts ect are left out). The pinion and spur are undetermined. I am unfamilure with the dynamics of the rather large tires that are used, so I am unsure what kind of final drive I will need. I am assuming that a gear reduction (before the pinion, such as the GD-600) is most likely going to be needed to turn the large tires.

THe pinion and the spur gears are pitched differently than the rest of the transmission.

Will I be able to get proper gearing without the GD-600 with a large spur and a tiny pinion? Or will I have to work the gear reducing gearbox into things?

Thank you,

Greg

 

[Ultima]

I would just try making it without and if that doesn't work than add them in, cause things like weight also affect it...

 

[Ace]

Tell us the tire diameter, how many teeth on the spur and which pinion yer runnin...

About 8-12mph is a good speed for crawlin. I use 15,000 for top motor rpm.

 

[Section8]

Hello, thank you for the replies.

Since I am looking for a more scale apperance, I was thinking of the K Rock, or the swamper version tire by the same company. Also looking at the LST tire. From what I have read (no experiance with these tires) they are about 7 inches in diameter. You would likely know better than me.

THe spur and pinion have not been purchased yet, so they can be anything (part of the problem). Though a tire size is essential information, I should have included it.

Thanks for the mph estimate. That helps IMMENSLY.

Greg

 

[Ace]

Okay, I'll assume 12 pinion and 93 spur...

93/12 X 32/15 X 32/15=35.3:1 ratio

(a stock clod is 30:1)

assuming 15,000 rpm motor and 7" tahrs gives 8.85 mph

(15k motor is fairly slow. Maybe use a 55t lathe motor, i.e what works in a clod should work for ya)

 

[Section8]

Hello,

Perfect. Thank you.

Though I need to get my head out of my butt. :roll: I arrived at a simular spur/pinion reduction (6.868, or a 96 spur with a 16 pinion, using 48 pitch) by working back from 10 mph at the tires over the course of a pages worth of wide space filler paper. :lol:

Though its nice to know I can still do math.

Since you assumed I was using 32 pitch gears, I imagine that they are what everyone is using. Is it possible to use 48 pitch, or am I still asking for stripped gears?

Thank you,

Greg

 

[Ace]

Actually I assumed you were running 48 pitch.

A 94 tooth 32 pitch gear would be about 3" in diameter!

If your running a heavy rig with 7" tires, I would be concerned about breaking gears if 48 pitch. Especially if any are plastic.

 

[Section8]

Hello,

Yep. Your right. My brain must have been going faster than my fingers at some point.

THanks again,

Greg