Getrag gearbox & prop-shaft

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Pete Boole
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Getrag gearbox & prop-shaft

Post by Pete Boole »

The Getrag gearbox has several kilogram of lead bolted to the rear of it. Given the Lotus weight ethos why would they do this? Does it have to do with vibration control? Where might all this vibration be coming from on a notoriously good gearbox? I think it's the prop-shaft - it is oddly designed (I think) - it has a u/j at one end and a CV at the other. This means that variations in the speed of the prop-shaft main tube caused by the u/j at the front are then carried into the rest of the drive train because they are not cancelled out by a second u/j at the tail of the prop. Does this make sense? What I'm getting at is that a "normal" prop with either u/js or CVs at both ends would make the lead weights superfluous, surely? What do you think guys?

Pete

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Lotus-e-Clan
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Re: Getrag gearbox & prop-shaft

Post by Lotus-e-Clan »

Some thoughts:

Is the unit length of the U/J and CV the same?
If not.
Is that because they were using back stocks of fixed length propshafts and the easiest way to make up the length of the shaft from diff to gearbox was by selecting (by length) off-the-shelf joints?

Or ..
Maybe (compared to the Beans box) the Engine /Getrag assembly without any additional weight rendered the combined unit 'nose -heavy' given the original fixed engine mount location - hence counterweight on the box to make the gearbox rubber mounts work better in 'tension' rather than 'compression'. Adding PAS and A/C to the front of the engine would in this case add to the counterweight issue?

Just guessing! :)
Peter K

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