Can Anyone please advise on the stud & thread size required for the rear stand on My 1939/40 WM20 ?
They appear to be in good shape but if worn oval which is the preferred method of recovery ?
Fill with weld then retap or threaded inserts ?
Thank You in advance,
Steve..
email (option): s.foster11@blueyonder.co.uk
Do you mean the pivot bolts? 5/16" BSCyc. Ron
https://www.draganfly.co.uk/index.php/component/hikashop/product/4430-
email (option): ronpier@talk21.com
Sorry Ron .
Yes , I did ..My error as I thought I had put this .
Is plug welding & retapping the best method for these please ?
Many Thanks again ,
Best wishes,
Steve..
Belay that ..Ive just looked at the picture & realise the design , thought there were threads in the frame member initially .
email (option): s.foster11@blueyonder.co.uk
From the M.20s I have owned the frame lug casting hole tends to go oval which has then been brazed and drilled to the original size. The stand bolts wear badly when the frame lug casting hole has become oval so it is a matter of replacing the bolts.
I am not aware that the frame rear stand frame lug casting was threaded - if it was it is not something I have seen!!
As for the rear stands themselves they do not appear to deteriorate around the pivot area.
This is what can happen if the holes become worn and/or you are heavy handed when pulling the bike onto the stand or you stand on the foot rests when kick starting. Ron
email (option): ronpier@talk21.com
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 Ron!
Long time since I write in the forum. My 1946 M20 rear frame bosses has the same problem as the bike in this picture. Do you still recommend to: " I'd cut them out carefully with a grinder and dremel and machine up a new boss and mig weld them in. They weld ok as they are made of cast steel not iron." as you did to Noam on a previous thread?
Thanks in advance and best regards!
Matías.
email (option): mbilamdjian@gmail.com
We tried 3 times to make a replacement arc and weld it into place & 3 times it failed
So finally is was described , a complete new boss welded in after the old one was ground out
Made up a dummy shaft to go across he frame to make sure the new boss was squarred up to the forks or the stand will lock up when trying to be used
The frame lug is actually a forging so welds beautifuly using steel rods
In our case we made up an arc section ( got a lot of practice doing that ) to replace the missing bit
Tacked that in place in situ then used that to hold the boss in place while the boss was being welded
We deliberately made he boss too long then after it was welded in we ground it back to be a close fit to the new boss .
On the next one we went one further and shrunk in a steel bush so it could be replaced then it wore through which is about 3 to 5 years of regular riding
If it is just worn oval the fill the hole with hard facing alloy and then grind that back so it is harder than the bolt.
The bolt is easy to replace the frame is difficult to repair
The next one I do I will use a high tensile bolt and a bush to replace the shouldered bolt
If you are not a stickler for authenticity then you can fit a stand clamp on the bottom of the guard to hold the stand and a weak spring ( or none at all ) on the stand itself.
What you have been told about the wear caused by the spring is quite correct
I overcame that originally by using some big bands cut from an innertube then inserted through the lower guard says on both sides so you lift the stand then hook the bands over each end
I will be making some tougher stand bolts for my project.
Mark
email (option): pes.sales@btconnect.com
The reason welding the rear stand lugs is not working and it keeps breaking, is all the cast frame lugs are made of mallable iron. Once you weld a piece of mallable iron it turns back in to cast iron due to the heat. You now have a very brittle frame lug which will crack under load.
There is a very important reason all the manufactures of the time used mallable iron and not cast iron.
The factories brazed the frames together as brazing does not get the lugs hot enough to turn them back in to cast iron.
How can you successfully weld mallable iron? I don't know? I am not a welding expert but bronze TIG welding may work?
For those that don't know, mallable iron starts out as a piece of cast iron. It is then heated to about 1700 degrees F for a few days until it gets a little soft and is now "mallable".
If the part gets really hot from welding, it turns back in to cast iron.
None of the lugs on your BSA M20 frame are mild steel or forgings. They are all mallable iron.
Many of the smaller factories used cast iron frame lugs because they did not have a forge .
BSA did have a forge, in fact they had 4 of them.
The really big drop hammer + 3 smaller air hammers plus some rolling forges but they are usually not considered to be a forge
The rear frame lug on every rigid BSA I have worked on was a steel forging and a simple spark test verifies this.
Some of the other lugs can be either steel forgings or iron castings and again I always do a spark test before atempting a repair because I have found the smae part to be made either way although the forged lugs are generally thinner due to the substantially higher strength of forgings .
As for malleable iron transforming back to plain cast iron I did not do enough Iron metallurgy when I got my degree back in 72 but SG iron is SG iron because of the chemistry and in particular the tin content .
In fact the local foundries used to make their charges from brake drums & tinplate .
Ove heating fine graine grey iron can cause grain growth and thus make the casting brittle but I have never come across a case of malleable iron becoming brittle due to reverson to grey iron.
Most cast iron welds fail becaue the welder does not do proper pre weld heating & post weld stress relief
Thanks Trevor, my metallurgy skills are a bit behind yours and I wouldn't have been brave enough to type that.
I'm only qualified to teach, inspect and design welds.
Mark
email (option): pes.sales@btconnect.com
I must say, I was a bit dismayed at Bruce's post as I had always assumed that BSA lugs and footrests etc were cast or forged steel, but I don't have the knowledge to argue it.:thinking_face: Ron
email (option): ronpier@talk21.com
I'm with Bruce on this one...I've argued the point for years that most, if not all, of the frame lugs (and other cast chassis components ) are malleable iron castings...Just as grey cast iron was generally used for barrels and heads for many years because it's one of the cheapest engineering materials, so malleable iron lugs were favoured for the same reason...
BSA were capable of producing forgings without any problem but it's the high tooling costs for forgings that determined they weren't used across the board...
I'm not a welder myself but I've had them tig welded on numerous occasions without any subsequent problems....I ensure they are allowed to cool naturally after welding...Ian
email (option): ian@wright52.plus.com
I'm only qualified to teach, inspect and design welds.
Mark
I torch weld so welding iron is never the problem it is if you attempt an arc weld .
As you know the preheating and post heating takes longer than the actual welding.
And FWIW I mostly used plain carbon steel coat hanger wire or old fence wire , not fancy alloy welding rods unless it is going to be a particularly big fillet .
I am yet to drag out the ASM handbook to triple check the SG iron post as I am more than capeable of getting things wrong but you would have to heat SG iron up in a reducing atmosphere for quite some time or use a massive amount of filler rod to either burn off the tin or dilute it beyond the critical levels .
Where as insufficient preheating will create a brittle weld / parent metal interface every time .
I ended up being a non-ferrous foundry tertiary metallurgist ( Recycling ) so irons & steels are not totally my bag but there was a lot of learing in 12 years of tertary education + 4 years of teaching and of course selective scrap for different foundries .
We used to use iron moulds for th aluminium & lead ingots which were all sorts of alloys because we had a standing order with 6 local iron foundries to pour our molds when they had to take a funace down to a low wash or had a massively out of spec load that had to be dilluted so we got the moulds really cheap, but repairing them was a nightmare as they could be any iron or steel alloy thus the use of spark testing
I do not like to toss qualifiations around on the web because everyone should independiently verrify everything they read on the web.
I could really be an 8 year old child with good computer skills who gets their jollies by fooling adults .
BSA were capable of producing forgings without any problem but it\'s the high tooling costs for forgings that determined they weren\'t used across the board...
I\'m not a welder myself but I\'ve had them tig welded on numerous occasions without any subsequent problems....I ensure they are allowed to cool naturally after welding...Ian
However most ( not all ) of the rear fork lugs I have come across are steel not iron and fracture / cracks do not have charasterics of castings and they are particularly thin
Castings are no where near as cheap as many would like to think.
While a set of forging dies are very expensive , a mould box is not cheap either , then there is sand & sand recycling , packing & baking the moulds , break out , cleaning + patterns , sprues & runners let alone the furnace itself and contol over the melt chemistry .
So yes it is cheaper than machining from a solid but the cost difference between forging & casting is not all that great .
For generations schools taught that "casting is the cheapest form of fabrication" based on the cost structure of grey iron casting very large items .
It looks like I have only Ian on my side!
I am not a metallurgist and my knowledge of the frame lugs is from what I have been told or read. So anything and everything I say is suspect.
Back in 1978 I bought a pre-unit Triumph with a broken side stand lug. A common problem from the owners trying to start the bike on the side stand. I went to my local Triumph shop to see about getting it fixed. The owner was Clyde Earl who had been Triumph's USA warranty manager in the 1960's until they went out of business. He said all the lugs on the frame were mallable iron. What it was welded with to repair it, I don't remember????
As BSA and Triumph were the same company and all their iron castings were made by Qualcast in Birmingham, I doubt BSA was using a different material than Triumph.
There is currently a company in Europe making new Norton frame lugs. They state they are made out of mallable iron just like the original lugs.
Phil Irving in one of his book mentions mallable iron for frames.
On BSA Gold Stars in I think about 1956, they started using forged frame lugs for the front motor mounts as the existing ones were breaking. Had they already been using forgings on the frame they would not have made the change. If we look at the rear wheel/rear stand mount which started this post, you can see it would be very difficult to forge this part do to the thin wall thickness where the tubes are brazed in. To forge it would require the frame tube holes be bored after forging which adds to the expense of the part. BSA was trying to make these bikes as cheap as possible and there is no need for a forging in this location as it see little loading and costs a lot more. Also if your forging a part you are going to use a tough alloy steel which adds even more to the cost.
As for a mild steel casting, not a good choice and it does not cast well and mallable iron has better fatigue resistance.
As for cast iron, the cheapest option but it is hard and brittle so likely to crack.
Now mallable iron, good fatigue resistance, casts nicely and cheap. A good clue is the parts are mallable iron is the foot pegs. When you crash your M20 and they get badly bent, there are no cracks anywhere on the foot peg. You can bend it back may times without problems. Mild steel, cast iron or a steel forging would crack after a few bends. As for welding mallable iron, at the point of the weld where the iron has melted, it turns back in to cast iron. I did a little research today and it appears that bronze or nickle TIG welding is the best choice. I AM NOT A WELDER SO ONLY KNOW WHAT I READ.
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 did a little research today and it appears that bronze or nickle TIG welding is the best choice....']
Irrespective of what the lugs are made of, and it seems none of us are 100% sure, the professional (coded) welder that does all my welding uses nickle/iron tig rods on the lugs...That has produced a reliable result to date....Ian
email (option): ian@wright52.plus.com
While BSA owned Triumph the businesses were kept totally separate , one of the reasons behind the ultimate demise of BSA.
Before BSA started making motorcycles they made FORGED FRAME LUGS for almost the entire pushbike industry.
Iron castings, in fact all sand castings can not be cast to finished size so the cast lugs are all machined to final size in any case.
White metals pressure die castings can be cast to finished size but few can achieve a surface finish that does not need machining.
You can forge just about any grade of steel.
Next time you are at a old trade fair, have a chat to the blacksmiths .
The grade of metal used is determined by the end use of the item .
The ends of most BSA mudguard stays are forged .
The head of nearly every bolt is either hot or cold forged
The threads on most modern bolts are roll forged
Every rivet used on every tank & every battleship was made by forging and placed by forging .
You steering stem is forged both ends to make the upsets to take the steering bearings
You seem to have a strange idea of what a forged item is and it's cost relative to casting.
It's a very interesting subject Trevor, and shocking that many people who claim to be some kind of mechanical engineer don't understand casting and forging. Also how a casting becomes a forging. Let alone the effects of subsequent heat treatment.
Not surprising as the education system in the UK is not fit for purpose.
Just because you google something, it doesn't make it correct. Most questions I ask, google doesn't have an answer.
It's a shame the internet wasn't kept for academics only. There would be a lot less rubbish to search through.
If I'm correct these frames were furnace brazed. So would have been heated to around 1000deg C. Any forging strength imparted would be lost by the steel being normalised. If in fact the lugs are steel castings and the carbon content isn't too high there shouldn't be problems with any kind of welding or brazing. The down side of electric welding is, if the carbon content is too high the heat affected zone can become very brittle without pre and post heating.
email (option): pes.sales@btconnect.com
['It's a very interesting subject Trevor, and shocking that many people who claim to be some kind of mechanical engineer don't understand casting and forging...']
It's not in the least shocking, no one has an encyclopedic knowledge of every area of engineering, though no doubt some claim it.....For example, you could be a mechanical engineer specialising in packaging machinery, pumps or guided missiles and have little or no knowledge of casting and forging techniques...Many processes that come under the general heading of 'Forging' have no relevance whatsoever to the potential manufacturing methods used to produce motorcycle frame lugs, like producing horse shoes...
The question of lug material is still lacking a definitive answer...I have found information describing the malleable iron frame lugs used on 1930s BSAs and also for AMC machines and there are references to the practice in 'Tuning for Speed' for example...I'm prepared to accept Phil Irving wasn't too badly infomed on the subject. There is absolutely no doubt they were widely used throughout the industry for frame lug components....However, though forging was also common practice (in many forms) was it used for wartime frame lugs or not..?....
That question is still looking for an answer and so far I haven't found any documentary evidence to suggest it was...Has anyone else?...Ian
email (option): ian@wright52.plus.com
And as we have just about exhausted the subject I will not add anything else
The fedintaive answer would be to do a macro section on a broken piece or an entire rear frame lug.
As I have not had access to those facilities for decades I definately will not be doing it .
FWIW I always do a spark test , you can google that fairly safely before doing any welding on anything I am uncertain of.
However if you do you should always test a couple of know samples at the same time .
So I have a destroyed B 40 foot peg ( cracked ) , a cheap supposedly drop forged shifter with a broken jaw and some 04 plain carbon from my scrap pile and a broken grey iron vice
And some times I do it 2 or 3 times just to make sure I am right because it is some thing I do not do very often .
We also have to modify what we think of as "furnace braized "
Most think of a great big kiln with rows of frames where in reality it would usually be an oven the size of a bread box slightly open on each side and the frame is only there for long enough for the precoated tubes to slide into the lugs
Usually they are as small as humanly possible because heat = money and would generally be of radient wall construction.
As suck the microstructure should not be destroyed unless it was left in there too long .
Again I did not work at the factory but there is every chance that the only piece that gets to red head is the section that the tube slides into
Quite doable on am M20 as the sides are separate so could pass through one side at the time but much harder to do with a swing arm rear end without over heating other parts .
Now days a "furnace braize " is usually an induction muff that is placed over the joint
Trevor,
I realize what forging is. If you take a piece of metal and hit it with a hammer, it is now a forging.
But as for BSA, why would they forge a rear frame lug? If you are gonna waste your time making a forging for strength, once it has been brazed that extra strength is now gone do to the heat. So now you have wasted your time and money making a forging which now has no more strength than a steel casting. What was the point?
Here in the USA, large heavy commercial trucks have forged chassis frames. They are marked on the frame "no welding" as the heat will destroy the strength of the metal.
Also the part in question, it would be very difficult to forge. As the wall thickness where the tubes are brazed in is too thin to forge unless you bore the tube holes later which adds to the expense. Forging this part costs more and gains you nothing.
Also a malleable iron part has better fatigue resistance than a forged steel part and is a lot cheaper to make as the frame tube holes can already be in the casting and only require a little bit of boring to clean up.
Also I was told by the person who was the USA Triumph/BSA warranty manager that all the lugs on a Triumph were mallable iron. BSA, I don't know?
Anyone who thinks that a forged part is cheaper than a cast part has never worked in the industry. And no I am not talking about a 5/16" CEI bolt which you cant cast. BSA most likely had a sand cast mold that could make 50 of the lugs in one mold at a time. If forging is so cheap, why did BSA not forge the piston?
All the lugs on a Vincent frame are malleable iron. If you don't believe me, look it up. Same applies to all the lugs on Ariel and Sunbeam frames who were owned by BSA.
As for spark testing a piece of iron or steel, a complete waste of time if you are trying to determine what it is made out of. It will give you an idea of it carbon content and hardness, but not what it is made of. It can tell you if you have a piece of steel or cast iron but not what type. For an unknown piece of steel/iron you are just guessing. You need a test sample to compare your part to. Only chemical analysis can tell you what you have. And as malleable iron has a lower carbon content than cast iron, I am guessing it will spark similar to mild steel? At work we had an X-RAY florescence machine which could identify metals. Sadly I have no access to it now as I am retired.
So BSA who owned Triumph, Ariel and Sunbeam used malleable iron lugs on these bikes but for BSA's they did not? Also you did not appear to see my post about BSA Gold Stars, they started using forged front motor lugs in about 1955 or 1956 (no one is sure what date). If the lugs were already forged, there would have been no point in making the change.
As for me, I am a retired electrical engineer. I ran a factory of 600 people. We did aluminum casting, welding, forging, electrical assembly and lots of other things. Many things people who worked for me did, they knew a lot more than me and I just watched. But I learned a lot of practical knowledge.
I am sticking with my idea that all the lugs on a M20 are malleable iron. Can I prove it, hell no!
Usually the "no weld " is because it interfears with the post forging heat treatment .
Most cold rolled fraim rails have "no weld" tags on them as well.
In order to soften the steel & destroy the forged grain structure you need to both heat and hold because solid state diffusion and phase changes do not happen instantaneously .
There are a whole series of TTT ( Time Temperature Transformation ) diagrams produced now days
People also need to understand that a weld is a casting and all welds have a cast microstructure.
Now specific to truck chassis
They are designed to use the minimum cross section of steel that will withstand the tensile & tortional loads of the fully laden truck + a safety margin
If Mike the moron welder does an arc weld with good penetration then he has replaced 1/3 ( or more ) of the cross sectional area with a casting and that is the real reason why you are not supposed to weld onto the chassis rails.
Even worse it will usually be in a strait line most if not all the way from top to bottom
If done properly a 1/4 wide weld bead will have a HAZ of less than 1/8"past the bead and a recrystalization zone about 1/2 that again.
However a 1/4" fillet bead will have a 1/8" deep penetration pool.
So from the surface, your 1/4" thick chassi rail has 1/8" of weld material ( with a cast structure ) + 1/16" of recrystalized steel + 1/64" of HAZ which has now severly compromised the rail and that does not matter weather th rail is forged, or rolled or pressed .
If you have a close look at the same chassis rail you will see welds done during manufactue and you will see they are usually vey thick beads , the extral thickness is there to compensate for the reduction of strength from forged / rolled microstructure to cast microstructure .
If furnace braizing is altering the microsructure in any way other than by some liquid into solid diffusion then the braizing is being bone very badly .
I suspect we're overthinking the question of material selection and repairs to frame lugs...:laughing: ...Hopefully some documentary evidence might turn up to provide an answer...Until then I'm going with malleable iron castings (as available anecdotal evidence points towards that) and the tried and tested welding methods I've used with success for years...Ian
email (option): ian@wright52.plus.com
They appear to be in good shape but if worn oval which is the preferred method of recovery ?
Fill with weld then retap or threaded inserts ?
Thank You in advance,
Steve..
email (option): binnawan@iinet.net.au
The second post...and then we went off at a tangent when repairs were discussed...:laughing: ....Ian
email (option): ian@wright52.plus.com
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
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
- BSA / Triumph, F8084, 16/02/1962, TJG, A50 & A65 Prop Stand Lug [F8085 (68-4752 Complete 68-4753)], EN3A STAMPING, NIL (BRAZED TO FRAME)
I don't know if this info helps anyones point of view or not?
email (option): steve@bsa-inc.com
It certainly does Steve and thanks for the post .
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 .
It appears they were using both from Steves post...So now the challenge is to tell which is which in the workshop...Ian
email (option): ian@wright52.plus.com