That gearbox weight....

[stuart]

14 hours ago, BlueTR3A-5EKT said:

Something says we used 119451 silentbloc bushes to service these lumps.  The bush is from the front suspension inner wishbone of Herald/Spitfire   Or was it 141481 the lower wishbone bush for IRS car front suspension.

No guarantee but perhaps worth a measurement.  Spit bush is 3/8” hole TR is 1/2” hole

Peter W

Not sure they are servicable, I ditched the one from mine as the large rubber section had separated from the centre bolt and would rotate.

Stuart.

[Andy Moltu]

Many have been ditched.

One can only speculate that they didn't work or did so little that their removal was not noticeable. Of course if the damping element had failed its removal was not going to be meaningful.

[Ralph Whitaker]

There was an excellent article in issue 324 of TRaction (September/October 2020) explaining why the damper was originally fitted and deleted again after the gearbox mounting flange was made thicker on the TR4, less clear why it was re introduced on the 4a on both normal and O/D gearboxes.

Ralph

[Ralph Whitaker]

On 6/26/2020 at 5:11 PM, Lebro said:

So would it be an advantage on a sidescreen car ?

bob.

Maybe not needed on the 1998cc engine, possibly introduced after engine went up to 2138cc so maybe resonance was harsher, deleted again after thicker gearbox bellhousing flange introduced, so I guess you and I with saloon gearboxes are OK.

Ralph.

[Lebro]

That's good !

Bob.

[Bfg]

Ian Gibson's shared with Technicalities  the Service Information sheets (May 1963) regarding these gearbox dampers, in response to a letter from John Scarr in TR Action #177.   

The document says that it was incorporated with the TR4, from approximately CT.18000, unless prior customers specifically complained of vibration between 2700 - 3000rpm, and then it may have been retro-fitted under warranty.  I guess after this, they were factory fitted to the TR4's and the TR4A as well, and to cars with overdrive (albeit perhaps with a different rubber bush). 

And that rev range relates to 70+mph cruising speeds of non-overdrive cars ?

Such a narrow vibration period would suggest harmonic vibration from the larger capacity engine, in sympathy with components in the drive train or other TR4-model car parts, perhaps noted as scuttle shake or panels humming at those speeds ?

Thank you Richard for your very kindly passing a copy of these on to me.

Pete.

[Bfg]

2 hours ago, Ralph Whitaker said:

less clear why it was re introduced on the 4a on both normal and O/D gearboxes.

On 22 December 1965 a temporary maximum speed limit of 70mph (112kmph) was introduced on Britain's motorways. The experiment initially lasted four months but was then formally introduced in 1966. The limit was made permanent in 1967.    TR4 and 4A drivers generally complying to the speed limits would particularly have noted this vibration period.

I had the same with a touring BMW motorcycle, whose vibration peaked at that same speed.  At 65 the bike was smooth, at 80 it was silky smooth ..but at 70mph it was quite uncomfortable.  In Germany, with their higher Autobahn speed limits, they might not have been so concerned but to British owners it was a nuisance.

In the US., where most TR4's went, I'm guessing that speed was again less of an issue. Possibly Triumph left the vibration damper off for some markets. If any customer complained then just that car was dealt with under warranty. This would have been cheaper than fitting every TR4 with it.   

Tr2 - 3A.  The first UK motorways were first opened in 1958 with the Preston By-pass.  It then took a few years before motorways became widespread, by which time the side-screen cars had been replaced by the TR4.  Quite possibly the earlier cars had the same vibration period but it wasn't of concern because few drivers would have sat at that speed for long on a smooth road. They'd just drive at a speed that seemed sweeter. 

Pete.

  

 

Edited July 2, 2021 by Bfg

[Andy Moltu]

Good grief - I didn't think speed limits applied to TRs

[Bfg]

 

[BlueTR3A-5EKT]

11 hours ago, Ralph Whitaker said:

Maybe not needed on the 1998cc engine, possibly introduced after engine went up to 2138cc so maybe resonance was harsher, deleted again after thicker gearbox bellhousing flange introduced, so I guess you and I with saloon gearboxes are OK.

Ralph.

Two more cylinders on that saloon engine as it is 1.5 Herald engines.   If that is the reason the weight was not on saloon cars or 6 cyl TR’s

Peter W

Edited July 2, 2021 by BlueTR3A-5EKT

[BlueTR3A-5EKT]

9 hours ago, Bfg said:

Ian Gibson's shared with Technicalities  the Service Information sheets (May 1963) regarding these gearbox dampers, in response to a letter from John Scarr in TR Action #177.   

The document says that it was incorporated with the TR4, from approximately CT.18000, unless prior customers specifically complained of vibration between 2700 - 3000rpm, and then it may have been retro-fitted under warranty.  I guess after this, they were factory fitted to the TR4's and the TR4A as well, and to cars with overdrive (albeit perhaps with a different rubber bush). 

And that rev range relates to 70+mph cruising speeds of non-overdrive cars ?

Such a narrow vibration period would suggest harmonic vibration from the larger capacity engine, in sympathy with components in the drive train or other TR4-model car parts, perhaps noted as scuttle shake or panels humming at those speeds ?

Thank you Richard for your very kindly passing a copy of these on to me.

Pete.

Do we have dimensions and or weights for the lump?

Peter W

[Bfg]

27 minutes ago, BlueTR3A-5EKT said:

Do we have dimensions and or weights for the lump?

Peter W

I don't. 

What would you want them for Peter ?

 

Edited July 2, 2021 by Bfg

[BlueTR3A-5EKT]

Curiosity’s sake.

Peter W

[RAHTR4]

Peter,

A complete "Damper kit" weighs a total of 3.83 lbs.

I can provide the size of the weight itself if required.

Regards, Richard

[BlueTR3A-5EKT]

20 minutes ago, RAHTR4 said:

Peter,

A complete "Damper kit" weighs a total of 3.83 lbs.

I can provide the size of the weight itself if required.

Regards, Richard

Yes please.

Peter W

[Ralph Whitaker]

4 hours ago, BlueTR3A-5EKT said:

Two more cylinders on that saloon engine as it is 1.5 Herald engines.   If that is the reason the weight was not on saloon cars or 6 cyl TR’s

Peter W

My TR3 only had 4 cylinders last time I counted. And it is a TR4 engine so might be worried if it had standard gearbox, but I was under the impression that the  weight was introduced to combat vibration,  and deleted again after the thicker bellhousing was introduced. All gearboxes after then having the stronger flange, inc the 2000 saloons that my box came from.

Ralph

Edited July 2, 2021 by Ralph Whitaker

[RAHTR4]

Peter,

The damper / lump of metal itself has an overall diameter of 3.1/2” and a thickness of 1.3/4”.

The weight of a damper with the silentbloc fitted is 3.20 lbs.

Regards, Richard

[RAHTR4]

Ralph,

The life of the damper did not end with the introduction of the stronger gearbox casing.

Engineering Change EC 7823 for the TR4A issued on 7th May 1965 states :

Vibration Damping Weight and Fixings introduced in order to eliminate Engine and Transmission noise and boom.

Thus the damper was installed on every subsequent TR4A until production ended, which was approximately 37,000 cars.

Regards, Richard

 

[BlueTR3A-5EKT]

1 hour ago, RAHTR4 said:

Peter,

The damper / lump of metal itself has an overall diameter of 3.1/2” and a thickness of 1.3/4”.

The weight of a damper with the silentbloc fitted is 3.20 lbs.

Regards, Richard

Thank you

Peter W

[Ralph Whitaker]

On 7/2/2021 at 7:09 AM, Ralph Whitaker said:

There was an excellent article in issue 324 of TRaction (September/October 2020) explaining why the damper was originally fitted and deleted again after the gearbox mounting flange was made thicker on the TR4, less clear why it was re introduced on the 4a on both normal and O/D gearboxes.

Ralph

 

16 hours ago, RAHTR4 said:

Ralph,

The life of the damper did not end with the introduction of the stronger gearbox casing.

Engineering Change EC 7823 for the TR4A issued on 7th May 1965 states :

Vibration Damping Weight and Fixings introduced in order to eliminate Engine and Transmission noise and boom.

Thus the damper was installed on every subsequent TR4A until production ended, which was approximately 37,000 cars.

Regards, Richard

 

Yes I realise that, see my original post above. John Kenyon`s excellent article also explains why they may not be any good today due to age hardening or softening of the rubber mount, or even with currently available replacement bushes, although your reply does make it clear why it was introduced again. 

Ralph.

 

Edited July 4, 2021 by Ralph Whitaker