The prewar stand is a different design than the standard WDM20, it is a nicely shaped casting and fitted not with a fork but just on the outside of the frame with pivotbolts threaded into the rearframe casting. So no oval worn holes in the framelug here...:relaxed:
You most likely have a rearframe which had this stand fitted, Stephen.
BR Michiel.
BTW, the WDM20 lugholes seems to wear oval not that much by using the stand but mainly while the stand is 'dancing' when riding. I noticed the right-hand side is usually more worn than the left-hand because the spring is on that side and gives more force on the pivot.
Hi, I've been reading through old posts relevant to my M20 rebuild and saw this thread and Bruce's comments:
Bruce, Dec 19, 2022 - 9:37AM
It would be nice if someone had access to the BSA drawings so we could see what they used. Actually maybe not a good idea as I may be proven completely wrong about everything I have said!
I have a number of BSA and Triumph drawings which I have shared quite widely, Mark Cook has had copies of a number of them, mainly those pertinent to the oil in frame BSA unit singles.
A number of the drawings are of frame lugs etc. There is some detail within the drawings which may be helpful(?). The drawings are all from the late 60's into the 70's:
Brand, Part No, Date, Drawn By, First Used On, Titl,e Material, Finish, Treatment
BSA, 82-9776, 23/01/1967, G F, A75, Offside Front Engine Lug, WHITE HEART MALLEABLE CASTING BS309 1958 W22/4, NIL, SHOTBLAST
BSA, 83-3088, 29/04/1970, C H Fellows, P34 (B25 / B50 OIF) Footrest Lug - RH, BS 970 EN 3A STAMPING, NIL, NORMALISED BY SUPPLIER TO 120-170H.B.
Triumph, QF7948, 17/11/1966, DG, P10 ?, Frame Bottom Lug, MALLEABLE CAST IRON BY SUPPLIER
A Stamping is a cold forging just so we understand each other
There are 2 main types of malleable iron, white heart & black heart , it is all about the carbon distribution
I did a quick search to find a simple understandable comparrison and came up with this one ( ignore the pearlite bit as they were a much latter developement )
https://www.mecholic.com/2018/10/types-of-malleable-cast-iron.html
Of importance & it should answer questions about why a forging would be used in place of a casting, note the times taken to heat treat malleable iron as comparred to the single heat & hammer used to make a forging
people seem to think I could cast a 100 frame lugs today, machine them tomorrow the braize the frames the day after
but as you can see it is a lot longer process than that,
even worse in wartime because most interuptions to the heat treatments mean that entire batch becomes very expensive scrap metal
Early on in the history when BSA was making models with almost no common parts then malleable iron becomes the least cost method.
however as production volumes increase forgings become a lot cheaper.
This was one of the reasons for the redesign of the new 1936 range, to bring in economies of scale .
