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Early Dual Sprocker diffentials, Vanderbilt racer Era

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Hello,  I have this question posted in the main technical section but I don't think the pre 16 experts have seen it.  Back in the day when the early Vanderbilt racers ( 1906 ) were built with dual sprocket rear chain drive the differential was behind the seat and attached to the bottom of the frame. When you watch the original films of the race on you tube,  the cars seem to come through the turns without skidding. This would rule out a locked  differential .   If the differential  was a open drive, there would be no need for the  second chain.   Therefore I would suspect a early form of posi-traction so both sockets would drive when the car was going straight. Several auto makers used this  style rear drive.  Did  each manufacture make there own  differential or did they buy the same unit from a manufacture?  If so who was it and did it have a posi-traction set up?   Attached is my Vanderbilt project made from many different period parts.( A work-in-progress)  Thanks  in advance for your expertise.  Stay Safe,  Life is Good,  Don Feeney


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Don. I have read recently that these units were posi-traction, or, perhaps better stated, direct drive. The outer wheel in a curve slipped in the loose gravel or sand of the early tracks, so the units worked fine for the day. Notice the chain drive disappeared at the same time tracks became hard surface. The chains were loose so that accommodated some play. As to whether there was one company producing the units I cannot say, perhaps contact David at The Old Motor, but the units could be severely undersized because there was little to no stress placed on the unit due to the chain drive. This made chain drive less expensive to produce. Also, drive sprockets were easy to switch out in the case of a hill climb over a road race where gearing could make the difference between a win and placement. This type of construction served the race car industry well up to 1911, when the Indy paved its track with brick. Today, the direct drive transmissions make the car harder to handle on a paved surface. One wheel has to slip for the thing to work. The rear of these cars are necessarily light but you can hear the tires barking as the cars round the bend on modern tracks. Your front sprockets are way undersized by the way. They should be almost equal to your rear sprocket.


I'm not an expert in these things, I'm just passing on what I've heard. Good looking project, by the way.

Edited by AHa (see edit history)
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