ratio of teeth on starter to flywheel

[mikesbrunn]

I am setting up a modern starter on a Locomobile and trying to figured out how many teeth I need on the starter . I had done this a 1910 REO and remember that there was a ratio that made it easy to turn.   thanks- Mike

[TTR]

Several things should be taken into consideration, not only the tooth count of ring and starter gears, but also diameters of the gears, taper angles and lengths of teeth, etc.

 

I’ve also seen incorrect set-ups were starter not only had unmatched tooth count, etc, but the due to inaccurate* mounting direction/location, engine was being cranked backwards, all which obviously had lead to some “starting difficulties”(!?!)

 

* Previously replaced starter appeared (no tags) identical to OEM design, but on top of having incorrect tooth count, it also rotated to opposite direction, all which the hacks working on it previously had not bothered to notice and instead attempted to compensate by introducing an 8Volt battery to (1928) cars 6Volt system... 😧🙄

Edited March 15, 2020 by TTR (see edit history)

[edinmass]

Most people today use a flat belt set up with a starter/generator. Less modifications and less expensive. 

[trimacar]

Ed, if using a flat belt on a starter/generator, then the unit is always turning when engine is running.

 

If you use, say, a 5-1 ratio, then if engine turns 2000 rpm, starter/generator is turning 10,000 rpm, way too fast.

 

How is this accounted for?

[edinmass]

We did it on a Stephens Dureya, Winston, and Apperson...........the cars rarely run over 1600 rpm, and we just run a pulley that gives good power to spin the engine. They have lasted years, and thousands of miles. Haven’t had a failure yet.

[Guest]

IMHO  if you, the driver can not crank it you should not be driving it.

[MikeC5]

This.

[m-mman]

I have always wondered about the difficulty or strength required to crank one of those early super cars.

Arent some of those Locomobiles, Pierce Arrows, etc. 500 or more cubes?  T-heads &  low compression yes, but still that seems like a lot of metal to get spinning. 

 

What is it like crank starting one of those beasts?  Before 1912 you really had no choice. 

[Guest]

If the ignition and fuel is sorted no problem.    If engine is cold.  Four cylinder or six needs three pulls up from 9 to 12 o'clock position with choke out, next pull ignition on as soon as engine fires start to unchoke the engine.  If engine is warm one pull with ignition off and next pull with ignition on.

Eight or twelve cylinder the same except maybe six pulls over with the ignition off.

It is not much different pulling a T-head Buick, a straight eight Buick a V12 or my Pontiac over top dead center.

If the engine is not properly sorted then all bets are off.

Most people make it a big job to hand crank an engine.  It isn't brute strength, it is technique.

[Bloo]

If you get a charge of air/fuel in a cylinder by cranking, and fire the ignition manually, the engine may start itself. My 1913 Studebaker is set up to do that, but I have only seen it work once. My starting method on a normal day is a lot more like what Tinindian posted.

 

Here are some guys starting the Blitzen Benz by firing the ignition. 1909, Four cylinders, 1312(!) cubic inches.

 

 

 

[joe_padavano]

25 minutes ago, Bloo said:

If you get a charge of air/fuel in a cylinder by cranking, and fire the ignition manually, the engine may start itself.

 

Interestingly, this is exactly what some new cars with stop-start technology do. The crank position sensor allows the computer to figure out which cylinder is on the firing stroke, and the individually-controlled direct injection and coil-on-spark system allows the computer to restart the engine by injecting fuel and firing the spark on that cylinder.

[DavidMc]

Trimacar,

In  answer to your question the starter generator units used are rated for very high RPM in generator mode.  I have a 2 cylinder Maxwell that was fitted with this belt drive starter set up by the previous owner .  The Delco Remy S/G unit is rated for maximum of 12,500 RPM and in fact needs to operate at 8-9,00 RPM before it generates current.  Mine was set up with 9:1 ratio so it slightly exceeded it max RPM when the engine was at its nominal maximum of 1500 RPM.  It all worked well but I took it off .