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57 frame difference

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57 frame difference

Posted by chris_cunliffe at Sunday 00:58

I have 2 57 dommi 99's one built Oct. 56 and one mid 57 both with M14 prefixes. I have just noticed a difference in the frames at the bottom rear engine plate mountings. On the earlier frame there are bosses, with a hole, on the outside of the lower tubes which the later frame does not have. Was there a purpose for these bosses and what if anything fixed to them

Re: 57 frame difference

Posted by richard_evans at Sunday 08:21

The 57 parts lists certainly don't show any bosses.  I don't have access to an earlier parts list.   Could they be anything to do with a side stand?.   The 57 parts list shows a clamp on type side stand.

Re: 57 frame difference

Posted by ian_cordes at Sunday 09:40

Not sidestand. The clamp-on ones fit farther forward, and anyway, are obviously only on one side. These bosses are on both sides, farther back. Also Richard, you mention the '57 parts list shows the sidestand, and as Chris pointed out, the '57 frames do not have the bosses, so are therefore not in question.

My '55 frame has them, and I have never ascertained for certain what they were for, and why they were considered unnecessary on later frames. One suggestion is they provided a strong fixing for a sidecar mount. That would make sense in that a long stud or bolt, with a spacer between the frame rails, would spread the load to both sides of the frame, contributing to preventing the frame from twisting. However, I am not convinced. The holes are too small for a decent sized bolt necessary for a sidecar mount, and anyway, at that time Featherbeds were not considered suitable for sidecars, the Model 77 being the twin sidecar tug of choice.

Re: 57 frame difference

Posted by chris_cunliffe at Sunday 14:07

Strangely, I have just looked at the 1959 parts book for 88, 99, ES2, and 50, and the frame illustration shows the bosses but I suspect the artwork is a carry on from previous parts books.

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