RA Bit by Bit

The frame for my RA project was altered extensively to an approximation of the later DT model.  Missing from the rear lower chain stay was the anchorage lug for the distinctive RA brake system. The lug was subsequently used on the OB model when it came out in 1924. In fact, so cleanly has the lug been removed it appears as if was never fitted. Judging from period photos, into 1926 and '27 RAs were being supplied without some or all of the brake components as the former road racing machines were being sold stripped down for the rapidly growing sport of dirt track racing. Yet where it can be ascertained, they all seem to have that particular lug present. Indeed, it continued redundantly to be seen on early DT frames.

And I needed one. Originally these would have been a steel casting or perhaps even a forging, but for the sake of replicating one plus spares, milling from billet was more practical.


It starts with a block of steel.



Pivot holes and their faces (as counterbores) from the outer face; that side facing away from the tyre.



Stood on end and the hole for the chain stay tube bored.



Flipped over and the faces of the pivots counterbored from the inner face; that side facing the tyre. The smaller hole for the reaction pivot has no counterbore as it is flush with the billet surface



Rough pass, inner face. Note cut has broken through to the counterbore from the opposite side.



Second rough pass with ball tip cutter.



Finish pass.



Thread milling.



Checking with homemade thread go/no-go gauge.



Production!


The first side was relatively easy as there is a square block to grab in the milling machine vise. The second side required some fixturing to hold the part.



Sawing away some of the excess material.



The fixture.



With workpiece installed. A crossbar is passed through the bore for the chain stay tube.



Rough pass.



Second rough pass..



Third rough pass. As this setup would not be as rigid as the first side grabbed directly in the vise, the roughing was done in three stages rather than two.



Finish pass.



All done.


To install over the frame tube, I will either need to split the lug or de-tube the chain stay from the frame. That will be a big job for another day.

To be continued...
-Doug

As noted in the listing this item sold in 2005.

-Doug

VERY INTERESTED IN THIS ENGINE. HOW MUCH TO SHIP THIS TO THE US? DAVE BAGNE 1025 DALE ST SOUTHWEST  HUTCHINSON MN 55350?

Quote from: My 4th bike on 04 Oct 2024 at 23:27 There are additives in these oils that can damage yellow metals in an older style gear box.

While this note of caution is well deserved, those days are long gone ?

My understanding is that this only applied to some oils, for a wee while.
Apparently the sulphur compounds involved/used could bond with moisture (and heat)
and form sulphuric/ous acids.

If this problem had been widespread, it would have eaten out millions and millions of automotive gearboxes
As it didn't, it seems to have been confined to a few specialist oil makers ???
Rectified as soon as it was recognized - the staining on the brass bits was an early indicator ?

QuoteOne of these hypoid type oils may give some slight benefits - if there is zero chance of any oils intermingling, or getting near the clutch.

Please be careful when using Hypoid gear oils.
There are additives in these oils that can damage yellow metals in an older style gear box.


Penrite T-90 gear oil. It's a GL1 oil made for older gearboxes and is equivalent to the S.A.E 50 motor oil.
https://penriteoil.com.au/products/transoil-sae-90

Hope this helps.

Aha.
Good advice !

The SAE50 tells you that Douglas recommended engine oil in the gearbox then.
Which makes it simple at maintenance time.
(SAE50 engine oil is the same viscosity approx as 90wt gear oil)

While oils have improved over the years, engine oil in gearboxes was very widely used,
for quite some number of years. In such a lightly loaded application, still good advice. ?

One of these hypoid type oils may give some slight benefits - if there is zero chance of
any oils intermingling, or getting near the clutch.
You'd want to have someone saying they tried it, and all was good.
Me not knowing precisely what is in a T35 box ...

My teutonic flat twin uses such an oil.
Maybe it ekes out some extra miles in the wear dept ?

According to the handbook, 1¾ pints of SAE50.

Regards, 
            Eddie.

What does the Owners Manual say ?
Always a good starting point.

Tropics shouldn't make any difference.
Change the oil(s) more frequently - if you habitually ride through thunderstorms !!

Relube ALL the lubing points also if this the case 
And wipe down/polish/oil all the paintwork and chrome to remove any lingering effects of salt spray .......
hth

Quote from: cardan on 06 Dec 2016 at 23:20 I'll try to put it behind me and move on...

Nope...

Fitting a pre-1910 Chater Lea belt rim brake to a (non Douglas) bike today, the threads for the two screws that clamp the mechanism to the chain stay are both 17/64-25, as is the threaded hole in the shoe where the operating arm attaches.

Lovely that the original screws are still there, with the rarely-used 1/8 Whitworth hexagon.

Mark down 17/64-25 as a Chater Lea proprietary thread that was enthusiastically adopted by Douglas.

Leon

1915 Douglas advertising/promotional brochure. with lovely prints of the current model range and the works as well as a photo of the works team. brochure details Douglas success in trials and in military use in the great war. it has the well known "Scotsman" image on the rear cover.
showing some signs of its (appx.) 110 years there is the remains of previous sticky tape repairs and the first few pages are loose the rest of the publication is hanging together well despite its age.
please PM me for further details.





















Photos cropped rotated as needed and converted to linked files - Dave, 01Oct2024