Looking for advice on pulley sizes

[wallfish 17,105]

My new project is going to need some adjustments to the standard pulley sizes. Instead of using the trial and error method, I would like some advice on the sizes to use or consider. I'm not trying to set any speed records or kill myself but definitely want her to move a little faster. I want to try and use low gear speeds as the normal high gear speeds and use high as the extra speed range if possible. I was thinking 4.5 OD on the engine and 3 OD at the trany but have no idea what the ground speeds would be. Thanks in advance for any help!

12hp with an 8 speed trany

[The Toolman 22]

stock frt an a 4 1/2" on the rear oughta get ya around 7-8 mph. Theres a copula threads somewhere here telling about it, an thats what they used.

[TT-(Moderator) 1,145]

I'm running a 4" engine pulley / 2.5" tranz pulley with 18" tall tires on my black tractor and can still start out in 3rd-high from a dead stop. (top speed is somewhere around 16 to 18 mph @ 4150 rpm)

I also found out quickly that I had to add some serious caster to the front end to keep it going straight.

In case anyone missed it, here it is on

[modracer 1]

well how fast do you want to go, my race tractor goes 80km/h lol but i dont think you want anything that intence.....if you give me the tire size and how fast you want to go at what rpm i can figure out what pullys you need

kyle.m

[VinsRJ 723]

Question: Where is there a good place to get quality pulleys? The cast aluminum Chicago pulleys at Tractor Supply make me nervous

I would also like to get a little more ground speed for The Rat..... got a couple other tricks going on before the show too :D

[MikesRJ 552]

These guys usually have exactly what you need (cast iron) in sizes from 1.75-7.0" Dia, and multiple shaft sizes for each diameter:

http://www.phoenix-mfg.com/acatalog/Fixed_...ve_Pulleys.html

[wallfish 17,105]

It seems the 4.5:3 ratio should work for me according to TT's experience on his tractor and they can always be changed if need be.

I wish I thought about the caster before I welded the front up. It could've been a very simple fix but it'll be a PITA now. Maybe toe in will help some but I doubt it will be enough.

Vince, I found these steel pulleys online at TSC in the correct sizes. I have been using the cast iron pulleys from Surplus Center for basic applications but I noticed they are marked as fractional hp. I feel more comfortable with them since they are designed for tractor applications. I wouldn't use those pot metal pulleys for something like this, they'll explode.

pulley page

This chart is for 3450 RPM engine speed