1960 Slimline Frame/Mudguard support

Hello Sean,

I don't know if these help, but mine's a 1960 99 Slimline Dominator, and I think these photo's may show what you're looking for?
On mine, the long bolt doesn't attach to anything on it's way across the rear of the frame, I'm thinking that it just adds strengthening support for the rear of the frame. If you want measurements, then let me know which lengths you need, I've got the tank and seat off at the moment.

Rear mudguards are known to rust at support area and fracture .the chrome grab handles should have carried forward to double the fixings and improve support to guard. We have welded plates inside the guards to stiffen. 

I don't know, but I suspect that the cross tube is there to support the back end of the half-mudguard on the DLs as they had a different part No. for it, the stud also secures one end of the lifting handle on them, I have never seen one of the DL type tubes though, so it's just a guess, but on the naked bikes it seems to be just a stiffener.

On a DL there is a tube brace  that stiffens the bathtub from the frame to the rear light . 

This shows the rear of my 1963.  This has a pair of upstanding angle lugs inside and above the rear suspension supports.  They are drilled to take the two pegs which project down from below the seat.  The seat doesn't rest on the cross tube.  Did they change between 61 and 63?

(The carrier is from 15mm copper central heating tubing, with end feed solder fittings.  The two forward projecting arms are also drilled, and the set pegs hold it from moving backwards and forwards.  1/2" lengths of garden hose act as spacers on the tips of the pointed pegs.)

Hi guys,
AMC at the time used similar rear frame braces on other models. The thinking was this. 
It strengthened the area between shock mounts. 
Each side has a strong tube of about 40mm welded to the frame tube via a steel vertical plate. Also strong. And keeping the distance between tube and frame short. 
The holes in each 40mm tube are fractionally over 3/8  inch and a very close fit to the long 3/8 inch stud. 
The holes in the 40mm tubes were made exactly (ish) in line by AMC. 
The long steel spacer is a tight fit between the 40mm tubes and is itself a close fit to the 3/8 stud. The spacer varies from model to model so that there is frame commonality even though some models have tool trays, mudguards and other paraphernalia supported on brackets welded to the centre spacer. 
All three spacers are very thick wall so that the flat machined ends, when clamped heavily together, contribute to the rigidity. 
It seems Sean's frame never had the strengthening cross stud. It would have left the factory like that and been deemed OK. 
However, if Sean goes ahead and wants the benefit of the AMC brace, I hope he appreciates it is more than a couple of plates and a stud between. 

Peter 

Hi I am a new boy to the group. I have just inherited a 1960 99, Dominator, it's been kept in a garage since 1975, it's in a bit of a mess, the exhausts are a complete write off. I am aware of a set from a 1958 Dominator, do any of you guys know if these will fit my bike. My frame number is R1491230. Thank you in advance for any help you can offer. Nick.

The early engines had a narrow angle between the engine exhaust outlets. The angle was increased later to open out the exhaust ports/pies so more air would flow over the head,
So the exhaust pipes are different.
Make sure you get the correct pair.
At least, that's my understanding of why the items I first got, were not correct.