Can someone provide the gear ratio output of the Happy Time engines? Had one apart & counted the gear splines? What is the rated RPM for a happy time. I don't own one but am working on some gearing calculations. TIA

Re: Happy Time Engine Gear Ratio Yes I am interested too. What rpm and what gear reduction off the gear box? I hear that Happy Time is happiest around 6000 rpm. I think I gave some info I could use if I was more formula familiar. Sorry, I better quit...

Re: Happy Time Engine Gear Ratio I believe it is approximately a 4:1 reduction from the crankshaft to the clutch shaft on the HT. Then whatever reduction off the drive sprocket to the wheel sprocket. I'll count tommorrow after work. Lenny, to find the ratio, all you have to do is count the teeth of the large gear and small gear in the clutch housing, Then just divide the large gear tooth number by the small gear tooth number to give you the value of X as in "X:1". Works the same way for chain drives as well.

Thanks for the HT ratio & RPM values. I developed a calculator in excel to see cause & effect on speed of tooth changes. My main goal is to examine the stock Sick Bike Parts jackshaft to include it in my project and see how it would work out on an existing 7 speed cassette and how it best relates to a NuVinci hub. Made one to show the basic HT install also. Tried to attach as a single page 30kb .pdf, but the forum limits are too small. Had to use .jpg instead. Can't attach as an .xls file either. If any one notes any errors, omissions or updated information, please post it.

That is really cool. I use ratiocalc.exe for my calculations. I would like to see or use your spreadsheet with other wheel sizes and clusters. Try posting it as zip file?

Wow.. 67 mph using the jackshaft setup. Thats given infinite horsepower, zero wind resistance and no friction though. Nice spreadsheet though. is that calculated using diameter of a standard cruiser/MTB tire?

wildemere, here you go as a .zip The jackshaft values of .000001 are hidden on the HT sheet. Had to do that to eliminate a divide by zero error and I made the book for the jackshaft first. datz510, Yes, I found metric circumference tables for bike tires on line, applied a formula to that table to gain circumference in feet. The table is included in the workbook as a separate worksheet. I'm looking to use the Robin EH035 on my cruiser. Just ordered the bike today from Worksman. The EH035 has a top end of 7500 rpm. I'm exploring various gear reduction options (Grubee, Staton & pocket bike boxes)

Aplologies to all. My Bad! I had the front two chainwheels that SBP provides inverted in the jackshaft formula's, hence the ridiculous speeds. Attached is corrected.