Roller Size and Mufflier Mufflers ?

Discussion in 'Friction Drive' started by WheeledWonder, Apr 2, 2012.

1. WheeledWonderNew Member

Hello Folks,

I've ordered a Honda GX35. I fully anticipate a motorized version of my bike will be much noisier. Are there any add-on mufflers that folks have found to be mufflier?

I am about 180 pounds. I'll be riding very level street roads. I'd like to take it easy on the horse, while doing the 20-25 mph range. None of the roller calculators I've seen are for Macs. I'll probably get a Staton rig. What size roller do you recommend? Is there a Mac roller calculator out there?

Thank you,

2. bigoilbobMember

Here's what loquin told me on that subject. Loquin has been most helpful and knowledgable in other posts to me, so it might be that do it yourself is the only way to go. Sure wish there was a kit or a bolt on parts list though. This is almost "build your own toaster" stuff.

http://www.motoredbikes.com/showpost.php?p=113108&postcount=26

3. WheeledWonderNew Member

Toast and DIY

BigOilBob,

Thanks for the guidance.

I like toast, and almost our entire lives are DIY.
What I hope is that tools like roller calculators can provide enough resolution to life's little matters so that I am either: a) off 1 click to the left or right, or failing that, b) spot on.

4. loquinActive Member

I threw together an excel spreadsheet three or four years back, and posted it here. If you don't have MS Office on your mac, download open office, and use it's spreasheet - it reads/writes to Excel.

The other approach is to just use a calculator.

I've simplified the calculation (combined units conversion constants and pi) as follows:
• English Units (Roller dia. in inches, speed in MPH):

MPH = D x RPM x 0.002975

or
MPH = D x RPM / 336.1

• Metric Units (Roller dia. in CM, speed in KPH):

KPH = D * RPM * .001885
or
KPH = D * RPM / 530.5

• Metric Units (Roller dia. in MM, speed in KPH):

KPH = D * RPM * .0001885
or
KPH = D * RPM / 5305

Note that this is the theoretical top speed. It does not take into account any losses in the drive train and the limited motor power we have available. Since these losses can include a great many variables, (tire rolling resistance, air pressure, rider weight/cross sectional area, riding position, etc.,) I don't even try to include it in the calculations. I added a full MPH to my top speed just by changing the OEM cruiser bike tire with a semi-slick tire. (Theoretical top end, 29MPH, OEM Tire Actual: 27, Semi-Slick Tire Actual: 28.)

Last edited: Apr 2, 2012
5. loquinActive Member

BTW, WW - the Honda spins at about 7800 max, with max torque at about 55-58 hundred. Here's a list of calculated top ends for various roller diameters at 7800 RPM:
• 7/8 inch roller: 20.3 MPH
• 1 inch roller: 23.2 MPH
• 1-1/8 inch roller: 26.1 MPH
• 1-1/4 inch roller: 29 MPH
Multiply these speeds by about 0.75 to get the speed at which you'll have the most torque.

Based on your 'specs' I would go with either a 1.125 or 1.25 inch roller. The 1.25 inch roller would allow you to run at a lower RPM, and be at peak torque/power at about 22 mph; the 1-1/8 inch roller would have peak power at a little less than 20 MPH. (If you were in a hilly area, I would suggest the smaller roller, but since you're on the flat, I would pick the larger.)

As mentioned often elsewhere, tire sizes don't matter with friction drives - only the roller diameter and engine speed.

Last edited: Apr 2, 2012

Thanks Lou