what is a pony motor?

   #1  

Anonymous Poster

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The way I understand it, a pony motor is a small motor that gets the larger main engine started. How does it work specifically though? I have heard about vintage tractors with this feature, but have always wondered how it works. Does anyone have a picture of a pony motor mounted on a tractor? Is "pony motor" the correct term?
 
   #2  

Robert_in_NY

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That is what it does. You get the little motor spinning quite fast then you pull a lever which engages it to larger motor to start spinning the gears. The larger JD 2cylinders had these as a option and they mounted so that they really didn't stick out like you would think. They were mounted under the sheetmetal and blended in nicely.
 
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Egon

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Pony motor:
Correct terminolgy.
Probably not used anymore but in the past it was a small gasoline engine that would be used to turn over the main diesel till it started. This little gas engine would start easily exspecially in cold weather. Almost all the "Cat Equipment" had this feature, as I recall. Also called a pup motor. Most diesels of the past era had one.
Egon
 
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Redtractorman

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A pony motor is a small 4 cylinder(on John Deere's)engine .For deisels you started this first as soon as it warmed up a little,you pulled a lever and it engaged the deisel and spun it while it also had the exshaust hooked to it to warm the deisel and them you turned the key and they deisel started up.I had a 720 and it would start at 10 below this way.
 
  
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I appreciate the information. I wonder specifically what happens when the lever is pulled though. What type of mechanical connection is used between the two engines? Is it a belt connection that goes from loose to tight? Is it a one way clutch type connection? I think that some of the old technology was very clever in a lot of ways, and some of it interests me.
 
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RonL

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I think you will find a lot of interesting information on the VanNatta logging site.

RonL
 
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Egon

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If memory serves me correctly the Cat equipment had clutch to gearing. Two levers. one clutch and one for gearshift. The pup motor had to warm up before being able to turn over the main diesel. Almost all of them worked this way. Don't think any used belts that I recall.

Egon
 
   #8  

MJB

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On the Caterpillar equipment I am familiar with, the pony motor drives the main engine by way of a pinion gear just like a normal electric starter. There would be either two or three levers to operate the pony motor. On the two lever units one lever was to engage the drive pinion into the ring gear on the main engine. This would be done while the pony motor was warming up. Once the pony was warm the second lever would engage a clutch between the pony motor and the drive pinion to turn the main engine. On the three lever models the third lever would allow you to select either high or low gear on the pony motor. Once the main engine started it would automatically kick out the drive pinion from the pony. In cold weather the pony motor may have to turn the main engine for 20 or 30 minutes before starting. The pony motor shared its cooling system with the main engine and the exhaust pipe from the pony was routed through the intake manifold for the main engine in order to warm it up. This was a great system for a few reasons. First the main engine never started without first building up oil pressure. Second, since it took some time to start, the operator had an opportunity to check the machine over and grease fittings while waiting for the machine to warm up. Thirdly, time was on your side. The longer the pony motor cranked, the more likely the main engine was to start. This is just the opposite of electric starters. In many ways the old equipment was actually designed better than the stuff being built today.
 
  
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Thanks a lot for the information. That was the description I was holding out for. Some day I might just lose my mind and try to find a vintage tractor. Thanks again.
 

Robert_in_NY

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I was just checking my JD parts CD and they call the pony motors "Cranking Engines". It ties in direct to the main engine and works just like MJB said the CAT's do.
 
 
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