[SEL] Gear Ratio Advice-Driving the Tod Engine

[Tod Engine]

I'm trying to come up with some way to eventually drive the Tod engine with 
electric, since steam is out of the question and air also isn't practical or 
economical.  I think I may have found a way to use a piece of equipment on 
hand.  In the former Youngstown Sheet and Tube 9" bar mill building is a 
homemade scrap baler, a machine that would coil up scrap wire from a rolling 
mill into a big roll that would then be fed back to the furnaces to remelt. 
I think the baler's electric drive would work to run the Tod with some 
modification.

First, I would like to be able to operate the Tod at about 12 rpm.  The 
operating speed for the engine was 75 rpm, but thats way too fast for just 
display.  Plus we are looking at over 150 tons of revolving and 
reciprocating mass so I don't want to get it moving too fast!  I think 12 
rpm gives it enough speed to be interesting to watch but slow enough to make 
me feel safe running it.

The scrap baler has a 15 hp 230 VDC motor which has a nameplate speed of 
between 400 to 1600 rpm.  It drives a huge gear reducer which has a 
nameplate input speed of 1200 and says is designed for 18.9 which I 
interpret as being an 18.9 to 1 reduction.  Then the drive shaft goes to a 
15 tooth pinion driving a 50 tooth spur gear.  So assuming a motor speed of 
1200 rpm I come up with 63.5 rpm out of the reducer then by dividing the 
number of teeth in the spur gear by the pinion I come up with 3.33 or 3.33 
to 1 ratio.  63.5 divided by 3.33 is 19 rpm.

Now my option is to just leave it at that and adjust the motor speed to get 
my 12 rpm or I could put another set of gears with a 1.5 to 1 ratio to get 
12.66 rpm.  I like the second option as I have no idea how many amps and 
horsepower it will take to get 150 tons moving from a dead stop, and the 
more reduction in the drive train the more mechanical advantage the motor 
has.

Now I ask the advice of anyone who has some mathematical background to check 
my figures.  Am I on target with my calculations or have I gone way off? 
Math is not my strong suit by a long shot!  Will this idea of mine work??

I like the idea of using the scrap baler drive for the following reasons. 
First it was homebuilt by Youngstown Sheet and Tube and is about as old as 
the Tod so it fits in.  I didn't want a modern AC motor and gearbox that 
would look completely out of place.  Second I really like the old type DC 
electrical equipment that was universally used in the mills.  The drive 
would be a mini exhibit in itself of old style DC power with barrel 
controllers, resistor grids and those big old loud contactors.  There is a 
practically unlimited amount of DC electrical equipment around for me to 
assemble a control system.  The third reason is that its free!

I set up a new album with photos of the scrap baler at: 
http://community.webshots.com/user/todengine    There is a spare DC motor on 
a platform above the motor in the pics.  At 15 hp they draw 50 amps!  Geez!! 
Probably spike way up when starting to turn the engine but fall way back 
after it gets spinning.  We may someday get a DC overhead crane for the 
display building so I'll have to set up a way of making the DC.  I do have a 
rectifier with the capacity to handle the loads or I could go with a motor 
generator set.  Hmm, maybe a steam driven DC generator set?  Maybe both.

Rick Rowlands
Executive Director
Tod Engine Heritage Park
William Tod 34" x 68" x 60" Cross Compound Steam Engine
Youngstown, OH
http://www.todengine.org/
Photo Albums Online: http://community.webshots.com/user/todengine