Author Topic: Mark IV push rods (Read 11001 times)

Mike of Woking · « **on:** 10 Oct 2011 at 14:01 »

I believe the 4 pushrods are common to all the Mks and also the Pluses and possibly the Dragonfly. My push rods are very corroded / rusty having been left in a damp shed for many years by the previous owner, while the engine was stripped. So I thought I would get some new ones made up to a sample as I don't have the engineering drawings. These rods are very thin and as such need to be made of the right specification material or they will bend, wear or break under normal use.

Before any one asks, yes I am a member of the LDMCC, having just joined, shortly after I purchased the bike. ( 1950 Mark IV). And yes I am aware of the current problem at the moment with the post war spares situation within LDMCC, which is why I am appealing on the forum. I am also a chartered engineer, so I do have some capability in engineering and rebuilding classic bikes.

My questions to the forum are these:-

1. Does anyone have any new or used push rods that I can buy ?
2. Does anyone know anyone who can supply these, other than the LDMCC ?
3. Does anyone know what the specification of the push rod material ?

Unless anyone knows differently, my intention was the make the rods from silver steel, to retain strength and maleability, which I intend to carbon case harden to ensure that the surface wear characteristics are ok at the ends which touch the came follower and rockers.

Can anyone comment on this please ?

Kindest regards,

Mike of Woking

eddie · « **Reply #1 on:** 10 Oct 2011 at 17:59 »

Mike,
The pushrods you have were only used in the Mark series engines - the Plus had Dural pushrods with hardened steel inserts in the ends. The Dragonfly pushrods are totally different - alloy tube with hardened steel cupped ends.
In the past I have made Mk pushrods from 1/4" dia silversteel turned down to 3/16" dia for most of the length to leave just the 1/4" dia head. The head has a 1/8"radius dome and the bottom end has the same radius but, of course, does not form a full dome. Being an alloy steel, silversteel should be hardened by heating and quenching. On the pushrods I made, I hardened just the ends, and then tempered them back to a light brown colour.

Regards,
Eddie.

Mike of Woking · « **Reply #2 on:** 10 Oct 2011 at 21:14 »

Cheers Eddie,

You have been a great help on this. I will follow your instruction / advice. Another success story for the forum !

Do you also know where I can buy some piston rings - not currently sure of the size yet - could be oversize ?

Kindest Regards,

Mike of Woking

Doug · « **Reply #3 on:** 11 Oct 2011 at 07:12 »

Eddie, Mike,

Is not silver-steel a UK euphemism for various through-hardening tool steels? As such, unless tempered, I would not expect any malleability from it, nor could it be case hardened (or, it would be rather pointless.) But, for a push rod I suppose being dead-hard (unless tempered slightly), while not ideal, will still likely work satisfactory. Or I suppose one could heat and quench just the tips for a dead-hard condition.

-Doug

eddie · « **Reply #4 on:** 11 Oct 2011 at 08:44 »

Hi Doug (and others),
Yes, Silversteel is a through hardening tool steel that is available here in the UK in small quantities (usually 13" lengths) from most tool stores. As such, it is often the preferred option when making small quantities of any item, and can easily be hardened by heating and quenching. For the pushrods, I just heated the ends to cherry red and quenched in oil, then polished the ends and carefully reheated at a point about 1" from the end until the colours ran out to a brown right at the tip - then quenched the tip again. Using this method gives the required hard tip with a gradual reduction in hardness (and increase in toughness) as you get back into the body of the pushrod.
As you mentioned, being a through hardening steel, Silversteel cannot be case hardened. There seems to be an opinion in several quarters that you have the option of through hardening or case hardening, but as most hardening processes involve heating and quenching, the composition of the steel determines whether it can be case hardened or through hardened.
For those who are not aware of the heat treatment process, basic case hardening of low carbon steels involves increasing, say, the carbon content of the surface of the steel (effectively making it a high carbon steel) before carrying out the hardening process. This is done by heating the steel to a cherry red in a carbon rich environment - the depth of case being dependant on the length of time the steel is kept in this condition. The item is then quenched in the same way as through hardening steels, but of course, only the high carbon skin becomes hard - giving a hard, wear resistant surface but backed up with a much tougher core to maintain better strength (heavily loaded items like camshafts and crankpins are typical examples of components that have to be tough while having a hard, wear resistant surface). Moving on a little - why are postwar Douglas conrods copper plated? This is another part of the case hardening process - some components need to be selectively case hardened and the copper provides a barrier to the absorption of carbon. So the conrods are made, and copper plated, then the copper is removed from the bigend eye and it's side faces. Under these conditions, only the unplated areas get case hardened - giving a tough rod with hard bearing surface for the bigend without having to resort to fitting a hardened liner.

Regards,
Eddie.

trevorp · « **Reply #5 on:** 11 Oct 2011 at 09:45 »

mk1 pushrods were also a smaller diameter than mk 3 onwards

eddie · « **Reply #6 on:** 11 Oct 2011 at 10:23 »

Trev,
I think you have got that wrong - Mk1 pushrods are the same dia but shorter than the Mk3 onwards type.

Regards,
Eddie.

trevorp · « **Reply #7 on:** 11 Oct 2011 at 12:34 »

Interesting the ones in my mk1 are thinner by half than my friends mk3, they may have been made up before i got bike, were the generator sets smaller in diameter or the same, i may have to change mine ill try and get some pics

Dawn · « **Reply #8 on:** 11 Oct 2011 at 13:23 »

May I ask a question?

Are the pushrods required urgently & do you intend running the bike before the end of this year? If not, why not wait until post war spares re-open? I do know they have loads of push rods & may be cheaper & easier to wait a little while??

In the meantime - I'll have a look in the garage for you.

Dawn

Mike of Woking · « **Reply #9 on:** 11 Oct 2011 at 14:11 »

Dawn,

It is good to hear from you.
My intention is to get the bike back on the road as soon as I can - so waiting until the new year for the LDMCC post war spares may not be a option. Your offer of some good second hand ones would be most useful. I imagine that my local firm would charge about £15 each made from silver steel, hardened and tempered to light straw as Eddie suggests. Added to this would be the base material cost (which would be peanuts). Please let me know what you would want for them if you find any in your garage ? Incidentally what part of the country are you in - are they collectable from Woking ? Otherwise it is the post.

I have some other Douglas spares that I could swap - if you are interested.

Does any of you know anyone who needs a set of Mark 3 / 4 front radiadraulic forks complete with yokes, caps and head light mounts - not sure if they are interchangeable to all Marks ?

Kindest regards,

Mike of Woking

eddie · « **Reply #10 on:** 12 Oct 2011 at 08:45 »

Trev,
The Mk1 pushrods were of the same type as the later Mks but were shorter. The generator engine pushrods had no head - that is they were 3/16" dia for the full length - but they had a collar 3/8" dia x 1/8" wide 1/2" down from the top. This collar kept the pushrod retained when there was a need to remove the cylinderhead.

Regards,
Eddie.

Dawn · « **Reply #11 on:** 13 Oct 2011 at 13:24 »

Hi Mike,

Had a look in the garage (at the spares from Dad) and am afraid there were no pushrods so you're out of luck.

Will ask around for you.

Regarding the Mark 3 / 4 front radiadraulic forks - they are not interchangeable to all Marks as with the Mark 3 Sports there is only one torque arm and the mudguard mounting is further up the forks where on a set for the Mark 4/5 there are 2 torque arms & the mudguard mountings are a little lower down (than on a mark 3 - on a mark 3 sports the wheel comes up to the mudguard saving it having a battering with pot holes) Am not sure about standard mark 3's.

All the best,

Dawn

Mike of Woking · « **Reply #12 on:** 13 Oct 2011 at 14:43 »

Dawn,

No worries - I have now taken delivery of the silver steel and should have some new ones made to Eddie's recommendations by the end of next week.

Kindest regards,

Mike of Woking

dragonmk5 · « **Reply #13 on:** 05 Nov 2011 at 14:44 »

I obtained a set of pushrods for my Mk1V from the club a while ago.
I take the view that, while it it possible to make certain components from silver steel, before deciding to embark down that road, I ask myself "what will be the repercussions if I get it wrong"?
In the case of pushrods, temper them too much and they will wear prematurely, too little and they may be too brittle and snap.
Based on that, I would wait and buy the genuine article.
I am looking to replace the rollers on the clutch actuating mechanism. I understand they are simply rollers from a drive chain.
It would be easy to make them from silver steel, but the tempering problem rears its head. The repercussion of failure of the rollers means engine out etc., so once again, I will wait til I find the correct item.
Scaredy cat? Maybe - but I don't intend to compromise the integrity of the rebuild by taking chances when I don't have to.
I have, however, made silver steel bushes for the gear selector forks, letting them down to a dark straw. These can be got at through the gearbox side plate, so I can keep an eye on them, once the beast is back in action. I am in the market for a gearbox in good working order though, as I fear mine might require parts that are not available from the club. Any-one got one to sell?

Mike of Woking · « **Reply #14 on:** 09 Nov 2011 at 13:23 »

Dragonmk5,

You view on life seems to be that making components from quality steel and tempering them is wrong. Yet you rely on the club supply which does just that, and indeed Douglas would have done just that when they were in business. The reality is that we are all human and if your assumption is that only the club source can guarantee the items to be perfect then you ar mistaken. The club simply uses engineering companies to make parts, like everyone else. These are made by humans - so mistakes can be made. As a practising engineer I suggest you are worrying unnecessarily and making something out of nothing. However I would never recommend that anyone makes anything which they are not competent or qualified to do. However you have to realise that a lot of us on this forum are suitably qualified and experienced.

On the subject of the rollers in your clutch, why don't you share the dimensions with us and hopefully we can help you source a standard product off the shelf which is made by a specialist bearing manufacturer. Most motorcycle clutches tend to use 1/4" dia x 1/4" long rollers, which are readily available from parts stockists, such as Norton, AJS and Matchless stockists (eg. Russell Motors) - but don't quote me on the size of your bearing, as it is along time since I had mine apart and I cant recall the size. Anyway I think that these are specified on the Mks Parts List as standard items with the dimensions provided. 9 Assuming that you one of these. Remember that like all motorcycle firms, Douglas would not make themselves what they could buy off the shelf from somewhere else.

I hope this helps,

Mike

dragonmk5 · « **Reply #15 on:** 09 Nov 2011 at 16:22 »

Wow! Well Mike -thats me told!!
As an ex toolmaker I am quite capable of hardening and tempering silver steel to the required standard and I CERTAINLY do NOT consider that contributors to this forum are incapable or inexperienced - in fact I have benefitted from advice from a number of members. The decision to buy components from the club as opposed to making them myself is a personal one and hopefully, one from which the club profits. I did not imply that making components from quality steel is wrong, merely that I choose to buy ready manufactured items. Where a company sells components that are hardened and tempered, it is likely that they have and use test equipment to ensure the correct hardness of the item in question, in which case, that is going to be as good as it gets - no guess work involved.

Thankyou for the advice re clutch rollers.

I sincerely apologise for the stupidity of my previous comments and for any offence caused. Please be assured - it was not intentional.

olesuffolkbuoy · « **Reply #16 on:** 09 Nov 2011 at 22:06 »

Gents,
Dont know a thing about your pushrods as my sole exposure to Douglas is a 1921 machine.
But on steel specs, I fear you are getting a little muddled.
Silver steel is a high carbon steel and not an 'alloy' steel.
In the absence of case hardening, any plain carbon steel must contain at least 0.9% carbon in order to form iron carbides - which are the hard bits! It may be hardened and tempered in the traditional manner as mentioned earlier.
Direct hardening alloy (tool) steels normally reside in the old EN16 range or better, achieve a full 64Rc when heat treat treated and may not be tempered after hardening. These materials are approaching high speed steel, which of course, exhibits 'red hardness'. It is the inclusion of chromium and other elements that make it an alloy steel, carbon making little, if any, contribution to its ultimate hardness.
Have a look around this site and you will see the different materials:-

http://www.westyorkssteel.com/silver_steel.html

I'd stay with your silver steel and follow the normal hardening and tempering route. At least its pretty machineable in the annealed/normalised state.
Hope this helps.
Tony

Mike of Woking · « **Reply #17 on:** 10 Nov 2011 at 13:17 »

DragonMk5,

Eitherway it is pot luck - whether you get parts made directly of thorugh the club . We need to be sure that the people making the stuff are completely profficient at hardening and tempering as you state.

On the subject of your clutch, I have checked the parts lists that I have and there are ball bearings on the thrust race and also 3 rollers on the lift mechanism. If it is these then which are hollow which you are looking for then please disregard my previous reference. Again I don't know what the dimensions are of these, but they do look like the rollers from a Renold chain. Why not buy a couple of links and experiment ?

Noted the comments of Tony, and yes my push rods are now made and have been hardened and tempered at the tips to light straw colouration. They look great. I did make them out of silver steel as per Eddie's recommendation. Although I did think about making them from Stainless at one stage.... But then I changed my mind.

This one is for Tony. With my oil industry background, I believe there was a widespread view that 316SS (Austenitic marine grade) could be case hardended - is that true ? As this combines the high tensile strength, corrosion protection, with surface hardeness. Also as a high nickel / chromium steel, it also has good work hardening properties.

Mike

eddie · « **Reply #18 on:** 10 Nov 2011 at 14:19 »

Regarding the 3 rollers for the clutch release - why not wait another 3 weeks and then contact LDMCC Postwar spares - they have a good stock of original rollers from the factory - so no worries about whether they have had the correct heat treatment!!!

dragonmk5 · « **Reply #19 on:** 10 Nov 2011 at 16:24 »

Thanks Eddie - that is exactly what I am doing. Will probably need a couple of other parts as well. I did try a local yamaha dealer to see if I could buy a couple of links, but without success. Am not in a rush as am waiting to see the outcome of the new barrels currently under manufacture. My barrels are +0.030 and will not clean up at +0.040 due to uneven wear. Not keen on going to +0.060, and, after the problem I had having a liner fitted to the barrel of my AJS whereby the barrel blew apart on the first kick under compression, I won't be going down that route again!

Doug · « **Reply #20 on:** 11 Nov 2011 at 17:12 »

Mark,

You are probably thinking of the Kolsterising process, trademarked by Bodycote. This is presently being use to surface harden 304 and 316 (austenitic) series stainless steels, as well as some other alloys unlikely to be encountered on a Douglas (like Hastelloy, Iconel and a few other exotics.) Basically the process diffuses carbon into the surface, akin to a carburizing process. While technically there is no limit to the depth (so claimed), standard processing is limited to a mere 0.001". So not very deep. It can achieve a fairly hard surface though, on the order of 70-74HRc. The depth is not sufficient to make austenitic stainless steel a good choice for a pushrod.

Both 304 and 316 can be cold worked, and the latter can be purchased in various forms pre-cold worked. It does increase the mechanical properties, hence why it is done with 316 medical grade implant raw materials, but not nearly to the extent one would claim a case hard surface.

-Doug