Input shaft - Wheel speed calculation

[simonelite501]

Can anyone explain how to calculate the wheel speed produced by the following:

Engine speed - 3000rpm
Aux gearbox 1.5:1
Diff ratio - 22:1
Tyre circumference 17ft

I need to know how to calculate it,not just the answer. Any help appreciated.

[stevieturbo]

http://www.vmar.com/java/gear.html

http://www.f-body.org/gears/

http://www.fatboyraceworks.com/gears/

http://www.geocities.com/z_design_studio/transmiss...

Although must say, some odd numbers in there..


A 17ft tyre ? thats kinda huge ? are we talking steam rollers ?

Ad the diff ratio, 22:1 is also big.

Edited by stevieturbo on Thursday 12th July 19:01

[stevieturbo]

Assuming its step down ? 1.5 ?

3000rpm/1.5 = 2000

2000/22diff = 90.9

So the diff outputs will be turning at 90.9rpm ?

17ft circumference, at 90rpm. will cover 1545 feet in 1 minute.

In one hour this will be 92727 feet

92727 / 5280 ( feet in a mile ) = 17 miles per hour ?

[simonelite501]

Ok, some more explanation required.

This is the vehicle


Tyre size is 30.5 x 32 inch, the gearbox is a 1.5:1 step up and I need to know how fast the wheel speed will be, and how to do the calculation.
Thanks for the links but I'm not sure they're of any use in this instance, the tyre size and gearbox ratio formula don't really fit this senario.

Edited by simonelite501 on Thursday 12th July 19:21

[stevieturbo]

Apply same calcs, except start with 3000x1.5 then ?

3000x1.5 = 4500rpm
4500/22 = 204.5 etc etc

ends up around 39mph I think ?

Edited by stevieturbo on Thursday 12th July 19:35

[simonelite501]

Using the same logic, I came to a similar figure, and thats not quite fast enough. I have the option of adding a truck gearbox which gives the top gear as .74 over 1:1 (direct drive) So, am I correct in thinking that if the input speed is 4500rpm, the gearbox is overdriving to .74 over direct drive, the output speed would be 7830rpm? If so, that would work out to a far more respectable 68.7 mph.........wouldn't it??????????????

[stevieturbo]

I know nothing of truck gearboxes.

But usually, most gearboxes step down, rather than up.

ie, output speed is slower than input speed, until the numerical figures go below 1.0:1

Cant you just spin the engine faster ?

[simonelite501]

It's a 27 litre V12 tank engine, maxium rpm is 3000, due to safety rules you are only allowed to overdrive the centrifugal clutch 1.5 times engine speed.
The truck gearbox is a 9 speed box (8 + reverse), the top 4 have been welded up so that makes it a 4 speed. 1st and second are under drives, i.e less than 1:1 3rd is direct drive and 4th is .74 over 1:1.
I just spoke to a mechanic with another pulling team and he said that the .74 over 1:1 comes out at 1.35:1 so that bruings us up tp 57mph, which is where we want to be, so I think the problem is sorted, well the maths at least. We've now just got to source the bits and put them all together........the saga continues.

[stevieturbo]

Not your average project !!!!!!