1975 SS Help with dimensions

[maelstrom]

Greetings all,
I need to get some dimensions and I hope some of you can help me out. I am building a chromoly frame for a bevel. I do have the frame drawings from the factory workshop manual as a start.

Update: Rick has provided me with the dimensions I have requested but this is going to be a difficult task. I have elected to get a frame scanned and have found a suitable technique to use. I need someone to take a suitable frame to be scanned, of course I will be paying the scanning firm. If anyone is willing to help me out then I will pay you for your help.


1/ the rear engine width between mounts. Should be the same for most models.
2/ the thickness of the rear engine mounting plates
3/ the internal and external diameter of the front engine mount lugs
4/ the external (found! 58mm) and internal diameter, beyond the race support, of the steering head. I know the bearing (639174) outer is 52mm
5/ the external diameter of the swingarm pinch lugs
6/ Fork offset. thanks Rick.
7/ Centre to centre swingarm to top rear shock mount
8/ Centre to centre swingarm to bottom rear shock mount
9/ If anyone has an original 3.50 V18 Metzeler C7 on the original rim I would like to know the wheel radius.

Thanks in advance.

[Rick]

I made hundreds of CAD drawings- bevel twins and singles, give me some time to dig through backup discs and I should have what you need. I can't find a way to add an attachment to a message here, so need to go through a longer process to add an image.
There were at least 2 different fork offsets- this drawing is what is usually called the 'flat' triple clamps, 26mm offset, 195mm between the tubes.

Rick

[maelstrom]

Thanks a million Rick. I sent you a PM.

[ducadini]

When You're building a cromoly frame, why not change a few things to get it steering a bit ?

Change the headstock angle to 28° and the rear fork pivot almost against the case (forgotten how much it moves forward).
Forkclamps with the least offset so You will be able to let go of the bars from time to time :-)

Don't forget the reinforcements between frontdowntubes, horizontal tubes and the toptube. Piece of cake when making one, troublesome when modifiying.

Nice winterproject (in the northern half)

ducadini

[maelstrom]

Mr Ducadini,
Thanks for your input. I am planning to build a fairly standard frame except for the materials 4130 (perhaps Reynolds 631). I will also make a monoshock version and finally something that is more avant garde.

Moving the swingarm pivot further forward is a sensible suggestion but I as I recall with my MHR. The swingarm is very close to the selector drum detent bolt in the back of the engine case. From memory you must have the detent version with the 1/2" sq drive to clear the swingarm. Not a problem with earlier right hand shift engines.

As for reducing the rake, I am open to this suggestion provided it clears the front wheel and can be shown to improve the handling. I think the Verlicchi monoshock had a claimed reduction in rake.

The trail increases as you reduce offset, since you are bringing your axle back but the point of steering remains that same. I think you mean to decrease trail? The bevels have a huge trail that has been quoted at 145mm. I could ride mine all day with no hands if I had cruise control. Trail has the greatest effect on steering so that I will approach with caution.

cheers

[Rick]

I have a 74 Sport, 74 SS, and a Verlicchi 'race' frame- all stripped down, so I should be able to get you what you need- most of the measurements were made from the bare Verlicchi frame, but I think the geometry you're looking for is the same. There is some variation between frames, and forget the four decimal place dimensions- I can't/didn't measure that accurately, just forgot to change my CAD settings. The steering head on the race frame is stepped- goes back to 52mm about 24mm down from each end- probably doesn't save enough weight to be worth the bother of chattering boring bars. These drawings were made for my own reference and use- I didn't plan to have them used by anyone else, so they're not really done, but the dimensions are accurate. Building a frame without another frame to refer to is a tough job- those top horizontal tubes have a tricky bend to them. And, I forgot to enable the metric dimensions.
Rick

1) 227mm to 228mm
2) 5mm
3) 32mm x 25mm, welded from a tube and a 'washer'
4) 48mm bored through, bearing cup shoulders 13mm to 14mm deep
5) 35mm OD, 40mm long, protruded through plate- welded both sided
6) 26mm
7) & 8/ see drawing

[maelstrom]

Thanks Rick.
I am afraid that you are correct and that this task will go on forever, particularly when it involves radii. The best option may be to get a scan.

If you or any other reader are willing to take your frame to be scanned then I will pay you for your effort. Please pm me regarding this.
cheers

[maelstrom]

As an aside, the page in the '75 workshop manual that gives dimensions to be used for the purposes of repairing the frame gives a rake of 29.5 degrees. With a 26mm offset and a wheel radius of 324.5, the figure given to me by Metzeler for the 3.50V18 C7 on a 2.15 rim, the trail would be 153.7mm. If we alter the rake to yield a trail of 145mm, the value I have seen reported, then the rake would be 28.3 degrees. Of course all of this assumes that the horizontal axis used on the diagram, front engine mount 14mm below swingarm pivot, is the same as would be used to cite the steering geometry values, that the tyre dimension is correct, and that my trig is not too rusty.

[maelstrom]

Rick has provided me with the dimensions I have requested but this is going to be a difficult task.

I have elected to get a frame scanned and have found a suitable technique to use, so I need someone to take a suitable frame (Sport/SS/Verlicchi) to be scanned. If anyone is willing to help me out then I will pay you for your help.
Thanks

[maelstrom]

Rick I seem to have lost the swingarm image that you put up. Could you make that available again with the dimensions for the axle slots and a horizontal view as well. Thank you.

[Rick]

Something went wrong over at Photobucket, all the photos I had there are gone, but I still have them. Not any interest from others, so I'll send them to your email address- I should still have your PM. Give me some time though...
Rick

[maelstrom]

Rick,
I found a print of the image you posted of the swingarm. I thought I had printed it but I misplaced it at work. Can you tell me what the basis is for the horizontal axis? I will still need all the other dimensions anyway. I shall wait in hope.
cheers