Dowty forks – anyone out there interested in a solution?

[efr215]

This post is an enquiry about how many people might be interested in a “final solution” to the leaky air springing of their Dowty forks.

The system I have in mind works on paper and I intend to conduct some trials soon having at last found a source of a suitable material to complete the design.

If there is sufficient interest I am prepared to look into making a batch once I’ve proved the idea but I would like to know the degree of interest as I would need to make some tooling. Just how much tooling depends on how many and while I’d like to offer as near to an “at cost” service as possible I really do have to recover my costs. (Another crumbly on a pension.)

Working on the basis of “first do no harm” the design involves some internal changes, (reversable), but external appearance would remain unaltered.

All observations gratefully received.

[Jan Buchwald]

Want to hear more
Jan B

[Steve Bowles]

OK – As long as we have some idea of what you are proposing and as long as it does not include springs – I’m interested in what you have in mind…

[efr215]

Hi! Jan, how many can I put you down for?
Hi! Steve, rest easy, no springs involved!

The concept first came to my attention as a result of my dealings with Stirling engines. The big brutes, (150KW), use Hydrogen as a fluid, a substance as fluid compared with air as treacle is to water. In other words it’ll leak through damn near anything and in this case it was at around 1,000psi with next to zero leakage over 12 months… I tend to make a mental note of things like that!

In the case of the forks the material will be different but then it’s not being asked to operate at several hundred deg. C. in an engine moving at 1,000 rpm! I know the idea works in far more arduous conditions than in a set of forks will experience but there is still a lot of work to prove it in this application and there the important matter of personal safety to consider.

This is then not going to be a quick fix, it’ll take some time to properly sort out, so bear with me please.

[Jan Buchwald]

I have but one Scott, and the forks are not leaking at the moment, but I am interested anyway.
Do you have any idea of te cost?
Jan B

[Mike Fennell]

Converted to springs last year but only in desperation. I was unable to
make them hold air in spite of new (expensive) seals from a Velocette
spares source, and very diligent polishing of the fork leg interiors.
In spite of all this I am intrigued by the proposed solution.

[John E. Smith]

YES! I would certainly be interested, but, like you, I am a wrinkly, so cost cannot be ignored.
Looking forward to learning more. Regards, John E. Smith

[efr215]

Before I go and hibernate with a cheap bottle of scotch ’till the “festive season” is over I thought I’d bring those interested up to speed on where I am with this idea.

My first concern was to do nothing that required any modifications to the existing fork parts. This I think I have resolved.

The second problem was materials, this has been a much more intractable problem than I would have ever thought possible and even now has been only partly resolved.
Why, Oh! why?!!! Won’t businesses reply to potential customers?

On the parts front I can see no way of doing this without making some new bits in addition to the new seal and this will inevertably add to the cost of conversion. The additional parts mostly involve turning and is within the capacity of my facilities so I’ll be able to keep the cost down to a minimum if that’s any comfort.

Question: As I have only the one example to work on if anyone else has been inside their forks and taken some measurement could they confirm:-

(1) That the full stroke of the legs is 5 .75″
(2) That the inside diameter of the upper tubes is 1.625″
(3) The correct quantity of oil each leg was supposed to carry?

A Happy Christmas to everyone and also my particular thanks to all those that sent me loads of useful information about Scotts.

[Author]

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