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Dave

2024-06-11, 20:02:05
Have you tried the new Drafts feature yet? I just lost a long message today and learned my lesson. It is a good idea to save a draft of any long post you are writing. You can then just keep writing and keep saving a draft, knowing you have a backup if there is a glitch. The draft is automatically deleted when you post the message.

Dave

2024-06-08, 18:30:04
For Sale
xman has two very nice 1950's machines available - a green 1950 mk4 and black 1951 mk5 - both in good condition and running well.

Dave

2024-06-07, 02:13:36

Dave

2024-06-03, 08:23:05
For Sale
Duncan has just listed his green and cream 1957 Dragonfly for sale with spares and documents.

Dave

2024-06-02, 08:34:05
Parts avalable
alistair still has parts available - barrels, carburettor, castings - see all listings.


Dave

2024-06-01, 18:33:27

Dave

2024-05-28, 00:09:46
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Douglas 2 3/4hp Valve Spring Retaining Collars/Pins

Started by pvn06, 01 Mar 2019 at 07:57

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pvn06

Another item I can now offer are the small valve spring retaining collars fitted to Douglas 2 3/4hp models.  These collars have a recess and a milled slot in their top face to retain a small pin that feeds through the top of the valve stem, holding the valve spring in place.
Again, another part I CNC machined for my own rebuild - from EN24T with Silver Steel retaining pin, available from our catalog at the following address:
https://racingnorton.co.uk/epages/4c675e64-813f-4c0a-8926-87a680c962a0.sf/en_GB/?ObjectPath=/Shops/4c675e64-813f-4c0a-8926-87a680c962a0/Products/%220729%20DG234_018%22

Best wishes,
Paul Norman
www.RacingVincent.co.uk


eddie

Paul,
         I guess you were working from a used collar when you produced these. I have seen the original Douglas drawing for them, and there is no half round slot for the cross pin shown on that drawing. The pin is located by just the rim around the edge.  If I can find the drawing, I will email it to you.

  Regards,
                 Eddie.

pvn06

Thank you for the update Eddie, it does not totally surprise me - and I appreciate someone far more experienced than I am with these engines in practice, coming back with useful updates.
That said, I am still not sure the original collar I was working from had not been modified itself, the indent/slot for the pin looks very pronounced, with no other noticeable marks around the recess. 

However, I only have a couple of manky other originals (hence why I wanted to manufacture new ones) - one of these looks like the slot is less pronounced (or just worn!), and the other still in situ on a barrel, but looks like it is badly worn.

With your advice, I have manufactured another set of collars, but to the original pattern you describe - i.e. just a recess for the full circumference - this is now Item 0730 on my catalog.

From an engineering perspective though - I still think the type with a milled slot to be a better design, in that it holds the pin properly captive - but most importantly stops the valve collar from spinning around the valve.  Since starting to acquire old Douglas 2 3/4hp engine parts I have seen a few examples of old worn valves where the top of valve (where the collar sits) is also worn in the same way as a valve stem wears at the line of the valve guide.  This does not seem like a good thing, and on most later design of engines (particularly where taper cotters are used) it is more normal the valve spring top plate is locked to the valve stem. 
I would be interested to take feedback from other owners with knowledge in practice - but until I hear anything contrary, will offer both types so anyone wanting to can try for themselves.  For my own part, I am still going to give the modified type a try in my own engine first, and will report back once I have done so.

Thanks for feedback Eddie, and see attached couple of photos of type without slot below

best wishes
Paul
www.RacingNorton.co.uk

pvn06

Thought might be worth showing a couple of photos of barrels and engine for my Douglas 2 3/4hp, now reassembled with new valves, valve springs and our retaining collars (the type with milled slots fitted).  a future article on the build progress so far to follow (when I can stop farting around and find the time!)

Paul

desmobikes

Do you have any more of these collets, I,m also after 2 pair of valves. yhanks, Bob