Bonneville salt flats---help

[NED FRY]

I was hoping Bruce would be on here -- but here goes-- I need help with the sprockets for my Bonneville salt falt barstool attempt-- It's a roller and rather cool realy---and I'm ready to mount my 42mt starter motor.I was worried about number of teeth on sprockets---before I mounted motor-- to make sure it wouldn't make a difference. any help out there ?

[KiwiMike]

I can try to help you out.
I'm assuming this is an electric BSR.
I need to know electric motor maximum RPM, front sprocket tooth number, rear sprocket tooth number and rear tire circumference in inches.
I will calculate your top speed for you.

[NED FRY]

thanks for offer-- here's the deal--- yes it's a required 12volt motor-- in this case a truck starter 42mt -- rules require one 12 volt motor and one 12 volt battery. No clutchs or gears only direct drive sprockets.--- tire are 10" OD. I don't know what sprockets to run. Read -on this sight under Elc Barstools--- Large 12 volt motors-- will give you an idea of what I'm talking about -- and once again thaks for help :o)

[KiwiMike]

Okay, I've done some research.
I do need the electric motor rpm to give you better figures.
Using 10" tires 33 3/4" circumference, they recommend a 5:1 ratio so that the motor revs out and doesn't lug.
So to beat the record assuming the starter does 7800rpm, you will need a 13 tooth driver on the motor and a 55 tooth axle gear.
This will give you 58.923 mph and a ratio of 4.231:1
This will give you some ball park figures to start with.

[nofuelstool]

we use a 40mt motor and with the ratio 1 to 1 have ran a little over 50 mph

[KiwiMike]

Okay, by my calcs, if the BSR runs 50 mph with a 1:1 ratio, then the electric motor is only pulling 1600rpm.
I'm assuming you are running 5" rims and tires.

[NED FRY]

Kiwimike--- the OD on wheels are 10" --the RPM is 1800.
NOFUELSTOOL--- what sprockets are you running--give me a statring place :o)

[KiwiMike]

Gidday Ned,
Thanks for the info. That saves me guessing.
Okay, 1800rpm with 10" wheels will give you 57.528mph with a 1:1 ratio.
The engine driver sprocket teeth will be the same size as the axle sprocket.
Take into account that the bigger the sprocket used, the less chain bind you will have.
Nofuelstool had it right at 1:1 ratio.

[NED FRY]

Thanks KIWIMIKE-- I was going to try a 20-drive and 25 axle

[KiwiMike]

No worries mate.
Keep in touch and let me know how it goes.
Post some pics.

[nofuelstool]

with a 10 tall tire the circumference is about 32 inches and the motor rpm is 8250. we use 32 teeth sprockets with a 35 pitch chain