After my air forks went down and would not come up, despite using my compressor, I eventually found that the 2 outer tubes were bent, starting at the bottom yoke clamping point, and up to 5mm out of line at the bush end. The piston and seal were way off centre at the fully compressed point hence the difficulty in inflating them again from this position.
So I am now looking at the following solutions:
1 Have my tubes straightened
2 Find some straight tubes
3 Move away from air but use springs, some straight tubes still required
4 Convert to Webb or Scott girder forks.My Flying Squirrel is around 1948 vintage, so girders could still be used. I have the double sided brake.
My question to the Forum is: Has anyone got the skills, parts or spares that would enable any of the above options to succeed?
I am currently having some springs made, but still need good tubes, and the girder fork option is high on my list if I could find some.
Welcome to the subspecies!
I too have a case of the Dowties! I also have several metres of new nearly-the-right-size steel tubing.
The trouble is the machinery in my little shed ‘aint big enough to resize a fifteen odd inch length to 1.625” I.D. and with a dead smooth bore.
What is worse in the soft South Eastern underbelly of this benighted country almost everyone else is too refined to get their hands dirty unless you call making loads of dosh creating nothing in the city “clean”.
The O.D. of this steel tube is correct and I can finish to the required length but you would need to be able to accomodate an I.D. of 1.590” as things stand. I am currently half way to figuring out a way of resizing a length. It can’t be that hard after all, they were boring cannon barrels several hundred years ago!
All of which rather puts me in mind of a letter written by Stevenson wherein he is waxing lyrical about a manufacturer he has found who could bore his steam engine cylinders “to better than the thickness of a thin shilling”.
James Watt’s design would not work without a precision machine tool was invented to do the job. Watt worked with Carron iron works for some time but they could not get the system to work.
Mathew Bolton knew of “Iron mad John Wilkinson” and his ability to dream up devices to do the job and so made a partnership with Watt.
John Wilkinson made the machine that made it all viable.
Mathew Bolton and James Watt made money
Who remembers John Wilkinson now–
As a long time designer and builder of special machines,– excuse the hollow laugh!
As regards the bore, it depends how much stock you want to remove.
Maybe a job for a long hone or a gun drill and hone.
Would it be more convenient to reduce the size of the internal components a bit to suit the tube you have if the tube has a decent bore.
I presume you have seamless tube?
Hello Roger, thought you might be along!
Yes, it’s cold drawn seamless and it measures 1.590” inside diameter so it needs 0.035” to be removed, that is to say 17½ thou. from each side. Rather too much for honing so some form of boring out first is indicated. Given the size I really need either a gunsmith who still makes punt guns, or someone who works for the Royal Ordinance! (Does it still exist? I know they closed Woolwich Arsenal and the Waltham Abbey Gunpowder Works because I bought stuff at the auctions).
Leaving the bore as it is would be OK if springs were going to be fitted, there is plenty of room for the bottom tube. If it was wished to preserve the air springing however then the problem of strange sized piston seals etc rears its head.
Oh! Yes! I do know what you mean about work, I spent over 20 years devising and making equipment for research work despite best the efforts of self serving dorks in suits more interested in their status and politicking than the job!
It’s not only John Wilkinson that is unsung, who remenbers Rosalind Franklin?
Many will know the following little tale which pretty well sums up my jaundiced opinion of managements.
A man is flying a hot air balloon and realises that he is lost. He reduces height and spots someone below.
“Hello! I have to meet some friends but have no idea where I am; can you help me?” he calls.
The man below tells him; “You are in a hot air balloon hovering approximately 30ft above this field in a location 51 degrees 31 minutes north and 0 degree 31 minutes east.”
“You must be an engineer.” said the balloonist.
“I am,” replied the man, “how did you know?”
“Well,” said the balloonist “everything you have told me is technically correct, but I have no idea what to make of your information, I’m still lost and still likely to be late for my rendezvous.”
The man below then said; “You must be a manager.”
“I am,” replied the balloonist, “but how did you know?”
“Well,” said the man below “you don’t know where you are or how to get where you need to be. You have made a promise which you have no idea how to keep, and you expect me to solve your problems. The fact is you are in exactly the same position that you were before we met but now somehow it has become my fault!”
If we ever meet in the flesh, remind me to tell you about how the captains of Japanese industry sent a team to the UK to discover how such a talented race could make such a hash of achieving commercial success.
It is a true and fascinating story, but their judgement was straight out of “O what a lovely war” Lions led by donkeys.
I think I would at least research the possibility of a seal arrangement to suit the tube you have, even if you use a different design.
I needed a special seal once, so I made a metal mould in two halves and had them made. You would need to find a small rubber moulding company who would tell you what they wanted. As regards gun drilling, firms like Mollart used to do this and I am sure that a forage through the internet would find someone, but as regards getting the bore to a surface finish suitable for seals, they might not get it right first time.
Sorry I do not have a ready made answer, I have never been asked to do that job. Kind Regards
That sounds about right!
What was the first car made is Japan?
The Austin 7
Jim although I can`t help with your dowty`s I can sell you a pair of Birmingham fork legs, which should be a direct replacement for them, if you are interested please e-mail me. Alan Noakes.
I can’t be 100% certain but I’m sure that there were what looked like ‘new old stock’ Dowty outer fork tubes among the older / used items that Gill Swan had on display at Stanford Hall – apologies if I’m wrong but may be worth a phone call.
Thanks Roy, I did see these tubes but they were internally threaded at the top, so I presume they were for the Birmingham Scott.