Question for the Engineers.

[Ol'89r]

For any of you ingineer types.

We have a 26 tooth engine sprocket.
A 58 tooth clutch sprocket.
A 17 tooth counter shaft sprocket
79 inch circumference rear tire.
7,000 engine rpm.

What size rear sprocket will we need to go 125 mph?

There will be a test.

 

[High Lord Gomer]

Not enough info....need to also have the numbers of teeth on the gears used for top gear.

 

[SpeedyManiac]

Ain't gonna happen...your internal gearing is way too low for it to happen.

Assuming:
1) Engine has the power to overcome wind resistance, etc.
2) Transmission gearing is 1:1 since you didn't give us any of that.
3) No slip at the rear wheel.

Rear wheel radius is 320mm (79 inch / 2 pi, converted to metric since I'm canadian). 125mph is about 56 meters/second. Rear wheel needs to be turning at about 175 rev/second. Engine speed is 7000rpm = 117 rev/second. Overall you'd need a ratio of 1:1.5. Seeing as the reduction from the engine to clutch is almost 2:1, you'd need a 1:3.4 ratio on the final drive. Or a 5 tooth rear sprocket.

Let me know if I'm wrong! It's early in the morning so I may have made a mistake.

 

[mideastrider]

I'm no ingineer by any means. My limited math skills would lead me to start with a rear sprocket in the 32-31 tooth range.

 

[High Lord Gomer]

If it is 1:1 in top gear, a 32 tooth rear would do it.

Engine teeth / clutch teeth * 7000 = Clutch rpm
26 / 58 * 7000 = 3137.931

Clutch rpm * drive gear / driven gear = countershaft RPM
3137.931 * 1 /1 = 3137.931

CSRPM * CS teeth / Rear teeth = Wheel RPM
3137.931 * 17 / 32 = 1667.026

WRPM * Circumference = Inches per minute
1667.026 * 79 = 131695

I/Min * 60 min / 12 / 5280 = mph
131695 * 60 / 12 / 5280 = 124.7112 mph

 

[Ol'89r]

Final drive is 1:1 in top gear.

 

[Patman]

Will you be wearing leathers or just a speedo?

 

[IndyMX]

Terry.. here's a program that will help you figure out exactly what you need...

So long as you know all the ratio's, just input them and you can play with the final ratio until you get the target speed.

http://www.mxboards.com/sprocket/sprocket.exe

It's also got a few other very handy features..

 

[SpeedyManiac]

Looks like this engineer can't do math...oops.

 

[High Lord Gomer]

LOL! I wore an engineer's hat one time. :)

I'm kind of wierd, I don't like having the title of "Software Engineer" because I don't have an engineering degree, but they can call me whatever they want as long as they pay me.

 

[holeshot]

OK, here goes another 6th grade math problem.....


7000 rpm x 60 (for rph) x (26/58) X (unknown ratio) x 79 inches travel for each rear wheel revolution = 7,920,000 in/hr (same as 125 miles per hour)


14,873,793.1 in/hr x (unknown ratio) = 7,920,000 in/hr

unknown ratio = 7,920,000 in/hr / 14,873,793.1 in/hr

unknown ratio = .5325

17/ teeth on big sprocket = .5325

teeth on big sprocket = 17/.5325 = 31.924

This is assuming a 1:1 top gear ratio

Now, quit making me work on my lunch break :coocoo:

And yes .. I am well paid (despite my homeless appearance)

 

[High Lord Gomer]

Damn crazy Russians....

If you had put in 58 instead of 50 you would have also gotten the correct result... 31.926

 

[Ol'89r]

Will you be wearing leathers or just a speedo?

Full leathers Patman. I don't want to take any of the thunder away from Gomer and his tutu. :yikes:

Looks like I need to change the engine sprocket to a 29 and the countershaft sprocket to a 20 and the rear to a 42. That will give us 125.2 mph.

Thanks guys. You guys are some fart smellers. :cool: :laugh:

 

[holeshot]

Damn crazy Russians....

If you had put in 58 instead of 50 you would have also gotten the correct result... 31.926

oooooppppppps ...... 31.926 it is. :whoa: Looks like I flunked 6 th grade. Post corrected. Can I get out of the corner of the internet now?


Damn... now I can't send O'LadyWhiner my bill.

 

[rmc_olderthandirt]

125 = 26/58 x 17/n x 7000rev/min x 60min/hour x 79"/rev x 1'/12" x 1mile/5280'

solve for n. N = 31.92


Rod

 

[High Lord Gomer]

Looks like I need to change the engine sprocket to a 29 and the countershaft sprocket to a 20 and the rear to a 42. That will give us 125.2 mph.

I plugged those numbers into my calculations and came up with 124.68.

Any chance it will pull more than 7K in top gear?

Can you easily change the size of the engine gear without also changing the clutch gear?

 

[Ol'89r]

I plugged those numbers into my calculations and came up with 124.68.

Any chance it will pull more than 7K in top gear?

Can you easily change the size of the engine gear without also changing the clutch gear?

Close enough for gubberment work Mike. :cool:

It may pull a few more RPM's but this will put us in the ballpark. Should pull to about 7,400 RPM. Can be fine tuned with the rear sprocket now.

The primary drive is through a duplex chain. So, yes the engine sprocket can be changed without changing the clutch sprocket.

Thanks everyone. Even you holeshot. :whoa: Gawd, now I'm totally confused. :coocoo: Crazy Russian. :laugh:

 

[holeshot]

Well....Terry...

Now that you have a ballpark number, I guess the real testing begins (you've probably already started). Did you go to El Mirage or other dry lake bed? How about members for a testing pit crew to hand you sprockets and stuff. Or do you already have enough "hangers on" and groupies :laugh:

What's the progress with this project so far?

 

[Ol'89r]

Hey Ron.

Haven't tested yet. Plan on doing that next week. Send me your email address and I will keep you in the loop.

You're more than welcome to come out and watch, help, cheer, sneer or whatever you want to do. :cool:

Been working non-stop on this thing. Ran into a few setbacks. Always unknown problems with a project like this. Sorry I haven't updated the Bonneville thread but there hasn't been any new news.