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Dave

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Throttle repair on 350cc Douglas 1930

Started by douglas1947, 28 Jan 2020 at 16:54

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douglas1947

Hi,

I hope to finish the restauration of my 1930 Douglas H3 soon. one of the last Problems is the repair of the throttle /air lever  body.
the slot for the air cable was broken and there was an old repair to keep the cable with some wire in Position.
The other problem is the fixing to the handle bar: there was a clamp with 2 small slotted srews on the throttle Body, looks not good.

I´m afraid there are no spares available. Has someone an idea for help?

Michael

douglas1947

2nd photo from top side (air Lever).

Michael

EW-Ron

I'm not familiar with that part at all.
But if its aluminium, a good aircraft welder could likely weld back the missing bits in fresh new aluminium.

Its amazing what those guys can do.
Usually found at small airports...

Doug

#3
Michael,

The fracture where the throttle clamps to the handlebar is a common defect. Here you can see on side of the clamp boss broken away:



The problem is the body is not aluminium, but Kingswood aluminium! (sarcasm) Kingswood aluminium is more like floor sweepings and the twenties and thirties crankcases can be a real challenge to weld. Given that this is a smaller part, it might have been poured from some of their better aluminium; that is with less contaminants. Only option is to try welding it and see. At least it should not have the issue of oil contamination, like a crankcase.

Doug


eddie

Having had problems getting Douglas castings welded in the past, I sought advice from an aerospace welder. It was to mechanically clean (wire brush) the parts first. Then set up the welding set so that the current is too low to weld, and the arc bias set to maximum cleaning. Then go over the joint so that the arc cleans the area without actually welding, wire brush again and repeat the operation. Make sure all parts are correctly positioned, set the welding machine to the usual settings and weld up as normal.
   Hope this helps,
                             Regards,
                                            Eddie.

Eric S

This is the kind of parts that my friend in UK might be able to cast from aluminium...

Dawn

Hi

There is normally a German guy at most of the autojumbles who sells what looks like a length of wire and using gentle heat can use this as a form of solder to fuse ali parts together.  I have used this to help put back together external parts on a fragile 274 carb.

Sorry cannot remember the guys name or the product, except its very expensive to use.

Cheers


Dawn

douglas1947

Thanks for all the advises.

Doug,
many thanks for the good photo of the throttle body to see the original clamp.
Do you have also a photo from the top side of the throttle body. This will help to see the shape of the missingpart of the air lever base.

Michael

Doug





There seem to be some additional holes, probably to secure it to the handlebar after the clamp broke.

Another, from my 1936 600 Aero.



-Doug

Jonathan Hewitt

Thanks Doug ,that's helped me with my Bantam throttle as well.
Jonathan

Eric S

Quote from: Dawn on 30 Jan 2020 at 11:32
Hi

There is normally a German guy at most of the autojumbles who sells what looks like a length of wire and using gentle heat can use this as a form of solder to fuse ali parts together.  I have used this to help put back together external parts on a fragile 274 carb.

Sorry cannot remember the guys name or the product, except its very expensive to use.

Cheers

Dawn


I met LB Restoration Services at the NEC in Birmingham. They sell such aluminum repair rods.
https://www.lb-restoration.co.uk/cgi-bin/store/commerce.cgi?product=RESTORATION&keywords=WeldingProducts&cart_id=1140601450.1725