Rubber engine mounts on Royale RP21

On my 1969 Titan Mk 5 the engine and transaxle bolt directly to the frame. On my 1988 Reynard FC car the transaxle and engine bolt directly to the frame. Anyone have any historical insite on why Rory Byrne would mount the engine and transaxle in my 1976 Royale RP21 on rubber bushings?

Obviously the Reynard's suspension is hung off the transaxle so it has to be solid mounted.

Looking around it seems like a very strange design feature. I don't think many cars did this. And they are a b*tch to change out when they get really, really old.

Upside is Dave Bean Engineering sells them. They are apparently common with some Lotus products.

I would assume they used them for vibration isolation. The ones on the gearbox are smaller OD, I couldn't find any when I tried recently, for a Titan MK6. When these get really bad, I'll probably go to nylon. I've never had trouble changing them.

Really common up to around 1978 or so, the Crossle 30 that I am finishing has them. I think they were there so the frames didn't crack quite as quickly.

Brian

Vibration isolation would be the natural reason to do it, but in a FF ? The obvious reason for NOT using them would be to get some stiffness out of the powertrain by using it as a semi-stressed element. I was under the impression that this was an unusual feature, maybe it was more common than I thought.

The ones Royale used are all the same but with 1/2" to 3/8" tubular sleaves in the ones for the transaxle.

Thank you for providing the information that the Mk 6 Titan Crossle 30 used them. Like I said, my Mk 5 does not, but that may have been a modification made over this particular cars life.

Dave,
The front "spider" engine mount on a Reynard has one.
The Brabham BT-21 FB car uses rubber mounts on each side engine mount and as I remember, my Mk6 Titan was basically a copy of this car.

Quote:

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Originally Posted by Dave Harmison

Anyone have any historical insite on why Rory Byrne would mount the engine and transaxle in my 1976 Royale RP21 on rubber bushings?

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Dave,

I could be wrong on this, but I thought Rory Byrne's first design for Royale was the RP24, which did indeed have solid engine mounts.

The frame on my RP24 cracked several times and had to be repaired. Vibration frequency was a killer and if you did not shim the mounts correctly to begin with you could crack it during assembly as well. Not a car that I would want to hit something solid in going backwards.

Sweet handling car but the RP21 was better looking.

Kip

Rory Byrne was the nominal designer of the RP21 - but the car appears to have some elements carried over from the RP3 and 16 which were designed by Bob Marston who came from Surtees. I just suspect it was one of those things that just was not changed until the RP24.

David,

Your Titan Mk5 should have metalastic bushings in the motor mounts and there should be two on the rear crossbeam that the hewland hangs from. I have replacements in stock.

Andy