Newbie with dumb questions

Hey guys I'm new here if what I'm posting about is inappropriate please delete me.Im restoring a home made "cart" from the 1940s for a deceased freinds grand daughter.Its heavy..prob 200 pounds at least and has 15 inch diameter wheels.I have a 13 or 15 hp engine for it and I need to figure out gear ratios with a jack shaft.I have used online calculators and I ve got decent results but I'm good with the moh my concern is that it will have enough power to get moving and not toast the clutch...here's the ratios so far..clutch 10 teeth,jack input 20 teeth,jack out 20 and axle 50 teeth...that equates to a ratio of 5.00 and 10.22 mph.keep in mind this is for a 9 year old girl...it just needs to drive around and be safe.is 10 mph too slow?Is this ratio gutless from a dead start??...Any help will be greatly appreciated,I have zero experience with this but I'm stoked to get on the welder and learn!!!
 

flattop1

Dawg 89
15inch wheels or overall tire height ?
I got 5.5 for a ratio . Which seems not low enough should be more 7/1 or possibly even more .
I think your mph is off as well it would probably idle at ten mph .
Nine years old 12-17 mph is probably good , you can change it later if it's not overly dangerous or she gets better at driving
 
15inch wheels or overall tire height ?
I got 5.5 for a ratio . Which seems not low enough should be more 7/1 or possibly even more .
I think your mph is off as well it would probably idle at ten mph .
Nine years old 12-17 mph is probably good , you can change it later if it's not overly dangerous or she gets better at driving
The over all wheel dimension is 15 inches with an 8 inch rim,thanks for the advice It definitely helps
 

Bob Evans

Grumpy Old Admin
Staff member
With a tire circumference of 47 inches, and I'm guessing the motor is governed at around 3600 rpm, speed should be somewhere around 32 mph.
You're going to need around a ten to one ratio to hold it to around 15 mph. taking your jackshaft output to a 10 should get you close.
 
With a tire circumference of 47 inches, and I'm guessing the motor is governed at around 3600 rpm, speed should be somewhere around 32 mph.
You're going to need around a ten to one ratio to hold it to around 15 mph. taking your jackshaft output to a 10 should get you close.
15 mph I think would prob be good,32 is way to fast lol,thanks for the advice.I ordered a 15hp engine this afternoon and I'd like to get all the sprockets,sprocket hubs and keyed shaft purchased asap so I can get crackin on this old project.
 
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