Brampton dimensions – similarities or differences from A to B.

[b'knighted]

Can any reader tell me any or all of the following, please? I can measure the C Girdraulic setup and may add them just for comparison but really need the comparative dimensions for pre and post war Bramptons. This is to try to work out which bits I've got and what it is safe to mix and match.
Is the head clip FF1 universal between all post war machines?
Is there a different equavalent to FF1 for prewar forks?
Are spindles the same lengths and diameter?

Dimensions required to compile chart. Answers 6 & 7 will vary but hopefully all others will be definitive.


1 A or B, Upper pivot centre to lower pivot centre when steering head is fitted to frame
2 A or B, Upper link pivot centre to lower link pivot centre on fork leg
3 A or B, lower link pivot centre to wheel centre on fork leg
4 A or B, Top link length
5 A or B, Bottom link length
6 A or B, Typical length from wheel centre to lower rear pivot
7 A or B, Typical length from lower fork spindle to top rear pivot

 

[Vincent Brake]

mine is at the paint striper now but in next week ill take some meaurements

 

[Oldhaven]

This is a 1948 B Rapide, but may be non typical due to taper roller bearings and Thornton coil over damper that allows setting preload.

1- 8 9/16
2- 9 5/16
3- 16 3/4
4- 3 3/8
5- 3 3/4
6- 19 3/8
7- 11 1/8

Ron

 

[b'knighted]

Thanks Ron,
You're first on the chart -
Measurement 1 may be affected by the taper roller bearings
Measurements 2, 3, 4, 5 should all be totally fixed and definitive for B forks.
6 & 7 may be affected by your enviable coilover damper.

 

[A_HRD]

Ian,

I think we've all been around this buoy several times over the years. I haven't looked recently, but I seem to remember there's quite a bit on thevincentdotcom too. In 2007 I started to make-up a document showing the differences between the A and B forks. I've attached it here for the record. Happy to receive constructive criticism in the interests of improving its scope and accuracy….

 

[bmetcalf]

"Top Links vary on both only as regards the stampings (HRD or Vincent-HRD)"

I wonder if Vincents stamped them or order them that way? (I admit - a pretty obscure question.)

 

[Oldhaven]

"Top Links vary on both only as regards the stampings (HRD or Vincent-HRD)"

I wonder if Vincents stamped them or order them that way? (I admit - a pretty obscure question.)

My links are stamped HRD only, and the steering damper knob is black ebonite, not alloy, though the fork damper knob is alloy, so there must have been some carryover or mixing of interchangeable parts. I imagine the links may have been stamped by the manufacturer if they were unique to HRD or Vincent HRD due to steering head angle.

 

[b'knighted]

Thanks Peter,
I've been through your document and it answers many of my general questions. You state that the B girder is 7/16" longer but don't say where the extra length is. As the headstem is 3/8 longer, 7/16" increase between the spindles at the front of the links would seem likely but hopefully other people will supply dimensions for comparison.
The only bit I can find on TheVincentdotCom directly conflicts with one of the differences you have listed. Where you state that the B headstem is 3/8"longer than the A, Humphrey says that the A stem is longer, but doesn't say by how much.
Perhaps I should have asked for a measurement of the A frame headstock to see if the change from cup and cup bearings to cup and cone demands the longer headstem but I can't imagine that it would need an extra 3/16" per bearing.
If all A & B links are identicle length it suggests that the B headstem must always be used with B Girders if the geometry is to be maintained.

 

[TouringGodet]

Is ebonite the same as bakelite?

 

[timetraveller]

No. Ebonite is a hard vulcanised rubber whereas Bakelite was an early plastic, think 1940s and 1950s radios