Goodwood crankshaft vibration damper

This forum is for non members to ask questions to the ATDC Members. Members should use the private forums for any and all Member to Member conversations.
Post Reply
Rod
Posts: 46
Joined: Sun Nov 24, 2019 9:44 am

Goodwood crankshaft vibration damper

Post by Rod » Tue Jan 21, 2020 7:54 am

One for the Goodwood experts among you:
My Goodwood (late 1938 build) has a one-piece [solid] crankshaft pulley instead of the expected rubber damped one, and it looks to have been on there for a considerable time. I suspect it is a contemporary Twelve item? I was wondering whether this was an official substitution, maybe because it was found late in the model run the original damper wasn't performing as intended, or whether it was simply that some previous owner fitted it because it was the only one available at that time.
The engine generally doesn't seem to be as smooth as I would've expected, given its conservative design characteristics and I do notice a discrete period of harshness through the rev range suggesting a torsional vibration issue. As far as possible, I try to avoid operating in this zone. Ignition timing is correct and engine mounts are in reasonable condition [i.e. not rock hard]
I'm not handy to a similar vehicle to do a comparison with so I'm interested in any info or feedback on this.
Or if anyone has ever sourced/fabricated a replacement damped one.
Thanks in advance
Rod

Geoff Pickard
Posts: 2
Joined: Tue Feb 11, 2020 10:10 am

Re: Goodwood crankshaft vibration damper

Post by Geoff Pickard » Tue Feb 11, 2020 11:26 am

I put an advert in the magazine and would be interested in sourcing a damper and would be interested in finding a patern, any ideas?

Rod
Posts: 46
Joined: Sun Nov 24, 2019 9:44 am

Re: Goodwood crankshaft vibration damper

Post by Rod » Mon Feb 17, 2020 8:39 am

I've only ever seen one other Goodwood [a '37] in real life, and it also had a solid pulley. Didn't go for a drive in that one but the owner mentioned how smooth it was to drive. He also mentioned in passing that he had spent more than the purchase price of my entire car on his engine alone so I suspect there had been extra special attention to crankshaft/flywheel/clutch balance/connecting rod masses etc on assembly.
Regarding manufacturing a replacement: There appears to be no way of calculating the mass of the flywheel member of such a damper or the characteristics of the rubber driving member without testing it on an engine. A guess could result in amplifying the torsional vibration to the point where the crankshaft fails. I have a third party Technical Bulletin- presumably based on the official Austin publications- which implies that the original unit was 'owner adjustable' as it advises: 'If periodic engine vibration is felt try tightening the six damper nuts one flat at a time. Nuts must never be slackened.' Which makes me think the original arrangement didn't meet design parameters and may have been deleted at some stage?
I did hope someone would come on here with an explanation or advice that they were 'available at xyz Ltd'.
Rod

peter_christie
Posts: 242
Joined: Wed Nov 20, 2019 3:46 pm
Location: Newton Mearns, Glasgow

Re: Goodwood crankshaft vibration damper

Post by peter_christie » Fri Mar 12, 2021 4:16 pm

Hello,
Maybe a bit late in this discussion, but I have a lot of experience with the New Ascot and I've always been interested in the "Fourteen" which shares much of the design of the New Ascot.
I have a collection of Austin Parts Books and Handbooks for Thirties Austins and I note that regarding a Torsional Vibration Damper, this is not mentioned in any of the parts books I hold. In fact, the Driving Pulley which fits on the nose of the crankshaft (the normal mounting point for a Torsional Vibration Damper) has exactly the same Part Number [1F84] as the same component on the 1535cc. Twelve Four engine for the same years.
Peter C. [6515]

Rod
Posts: 46
Joined: Sun Nov 24, 2019 9:44 am

Re: Goodwood crankshaft vibration damper

Post by Rod » Sun Mar 14, 2021 9:18 am

Hello Peter,
I have the "List of Spare Parts" publication 1785 dated April 1939 which is mostly correct for my car [some minor differences i.e. steering box and starter pull ilo push button solenoid exist]. It gives me 1F890 for the assembly [illustrated- as its a rear view, two of the damper nuts are just visible] and then a text list for the component parts [which I won't bore you with] ,evidently it was a serviceable item. BTW I still haven't found any more info on whether it was deleted at the Plant or what.
Late edit: Chassis FRA40145 which makes the car August 1938 build by my reckoning [I stand to be corrected on that] although the gearbox is stamped October 1938. Publication 1785 applies from 39 592 to 40 585 according to its foreword.
Also do you have correct publication number for the Body parts catalogue for these? I've only ever come across a FR series one, I'd like to try to get the correct one.

Post Reply