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Deleted User.
Deleted UserGood day once again. As suggested I removed the head and barrel together to fascilitate removal of head to replace head gasket. Very simple operation to do that and I was singing the praises of Mr Scott.
However trying to drift off the head from barrel is proving to be quite a chore. Several applications of penetrating fluid and considerable amounts of heat via a rosebud have failed to dislodge it in the slightest. I had made a drift of hardwood slightly smaller than bore and with a 5 lb hammer failed miserably to achieve the slightest famount of movement. I am reluctant to use anything larger as am afraid of doing damage to the head, not sure how much force itcan take. It is at present immerssed completely in a penetrating solution.
A friend of mine who has a collection of Rolls- Royces mentioned how some of their models had aluminum heads and the same thing occurs at times with them. He mentioned a special type of metal drill bit that is hollow that is slid over the stud and material removed(including corrosion) down to the iron block. This is rather drastic I think and once again am asking for suggestions. Another friend suggested simply immersing it in water for a week or so. Another mentioned the electrical process of removing rust from steel and iron with a battery charger. I have done this with great success on small steel bits but not sure what it might do to the aluminum. I am assuming what is happening here is the electrolisis of the two dissimilar metals and the resultant corrosion.
Any further ideas or processes I should try. I would think it is a very common problem to the model. Also when re-assembling what precautions should be taken to prevent re-occurence.
Once again many thanks for the help provided on this forum. Might get her on the road this year yet.
Regards
Brian
Deleted UserThere is one avenue that you might care to consider, sacrifice the studs; they are after all easy enough to replace and the least costly. The head gasket provides the obvious place to do the deed providing as it does a good sixteenth of an inch to put a cutter down.
I’m lucky, I have my own milling machine and that would be the best and safest way of doing it. It might be possible, with care, to do it by hand with a hacksaw or even jury rig a drilling machine. But even with the set of the hacksaw teeth ground off there is the risk of marking the machined faces. If therefore you were not totally confident I’d say entrust the job to someone who has the know-how and equipment. Sadly, until I get my new workshop up and running I can’t offer any practical help.
With the head and cylinder apart any decent press should be able to deal with the stud remains in the cylinder head. The cylinder casting is slightly more of a problem as each stud would need careful setting up so that the stud remains can be drilled out without damaging the threads in the casting.
This is not the first time that this problem has come up and I’m wondering how much extra it would cost to have sealing ferrules(?) as fitted on the head gasket to seal the bores also fitted around the water holes and stud holes. My feeling is that this would reduce water creep through the asbestos core of the gasket.
One final point, I am a great believer in anhydrous lanolin (wool fat), after all when did you last see a rusty sheep? Any good chemist will be able to get you a 500g tub that will last for ages. A thin smear over any surface will all but eliminate the risk of corrosion. I learnt its usefulness when sailing and anything that can resist seawater has got to be good! It can be diluted with white spirit and brushed on exposed parts or ones that are to be laid aside for long-term storage. It is also brilliant for protecting brake pipes and the like on the car and even helps, (for those that are compelled by ‘er indoors to do DIY), with household chores, driving woodscrews and the like.
Deleted UserI have a tank of red diesel with two Scott block / head units resolutely united.
Next to this is a prayer mat. So far religion has failed to come up to its reputation. I have tried the hollow tube cutter, but when a hard tooth breaks off down the hole, you are lost. So far experience favours 3 months in diesel, refit on to bottom half, convert old spark plug to take centre bolt, screw down till it just touches piston at TDC, make sure nuts are unscrewed two turns (I do this before immersing in diesel) Screw down spark plug bolt one turn, rotate flywheel to exert pressure on head, either clamp flywheel in position or ask friend to keep pressure applied on flywheel, Use aluminium drift and medium lump hammer to beat the nuts on end, each in turn and in rotation. Repeat for other bore. With luck the combination of diesel, applied pressure and shock will start it moving. If no luck, saw it off. If you think you deserve better, then consider that I volunteered to remove heads as a job. I must be crazy!
Good luck friend and if you find a better way, please tell us all. Roger
Ted RobinsonI am sure this has come up on the forum before but I have looked through all the posts to no avail. One method I remember was the welding rod on an industrial welder was replaced by a 5/16” diameter rod,it was applied to each stud in turn which heated up and expanded thus cracking the corrosion. I remember Jim Best had to cut a head off once and had to make new brass water tubes. When he refitted the head he enlarged the stud holes to give more clearance. I once made some new head studs and had them parkerised and they never corroded a process they used on shafts to prevent fretting. Unfortunately the factory where I spent most of my working life and was able to do this is now a large housing estate. Best wishes Ted.
Deleted UserHi Ted I have heard of this process but never used it. For anti corrosion I send to a local company who do blackodising and also phosphate treatment
I blast cleaned the webb fork blades plus fittings and had them phosphated which is a dull black finish.
It must be ten years since I had them done and not a spot of rust.
Given the time it takes to do a reasonable paint job, I now blast clean the flywheels after I have fitted new sprickets etc and have them phosphated. They look very smart and its cheaper than painting.
Company is
SPL Blacking
420 Thurmaston Boulevard
Leicester LE4 9LE
0116 223 6100
I do not think they are used to handling and repacking Work by post but if you needed I could handle that. Kind Regards Roger
ps I must try the resistance idea
Ted Robinson@Brian Rowe wrote:
Good day once again. As suggested I removed the head and barrel together to fascilitate removal of head to replace head gasket. Very simple operation to do that and I was singing the praises of Mr Scott.
However trying to drift off the head from barrel is proving to be quite a chore. Several applications of penetrating fluid and considerable amounts of heat via a rosebud have failed to dislodge it in the slightest. I had made a drift of hardwood slightly smaller than bore and with a 5 lb hammer failed miserably to achieve the slightest famount of movement. I am reluctant to use anything larger as am afraid of doing damage to the head, not sure how much force itcan take. It is at present immerssed completely in a penetrating solution.
A friend of mine who has a collection of Rolls- Royces mentioned how some of their models had aluminum heads and the same thing occurs at times with them. He mentioned a special type of metal drill bit that is hollow that is slid over the stud and material removed(including corrosion) down to the iron block. This is rather drastic I think and once again am asking for suggestions. Another friend suggested simply immersing it in water for a week or so. Another mentioned the electrical process of removing rust from steel and iron with a battery charger. I have done this with great success on small steel bits but not sure what it might do to the aluminum. I am assuming what is happening here is the electrolisis of the two dissimilar metals and the resultant corrosion.
Any further ideas or processes I should try. I would think it is a very common problem to the model. Also when re-assembling what precautions should be taken to prevent re-occurence.
Once again many thanks for the help provided on this forum. Might get her on the road this year yet.
Regards
Brian[/Hi,Brian, I think I would tackle the studs one at a time. After immersing in diesel I would screw a standard 5/16 BSF nut on the stud until it was just flush with the top, tack the stud to the nut with an arc welder then try and rock it back and forth with a suitable wrench. I think you would have more chance of breaking the bond than trying to release all sixteen plus the water pipes in one go. You could still use the studs if you wanted to by grinding off the weld or even skimming in a lathe.I dont know how long you would need to let it pickle in diesel I would not have the patience to leave it for three months I don’t think.
Deleted UserTed Robinson is correct about the heavy duty welder method of rapidly heating the studs to bright red along their whole length. The expansion crushes the accumulated corrosion products – according to American member Doug Kephart who wrote it up in Yowl several years ago. Are you still there Doug?
I always found that DK speaks with the authority of a very experienced and well equipped engineer – he admitted that not everybody has such a welder in his garden shed!! – and it would be nice to hear from him again on this topic. I can’t find the article in my haphazard collection of Yowls.
The postings do not mention a reference in Technicalities – page 2.4.30
where the head corrosion problem is discussed by Glyn Chambers and Ken Lack. This material goes back to Yowl V 9/10 1975/6 where it is stated that Spares Scheme stainless steel head studs were to be cadmium plated as part of a preventive solution to the problem. This apparently reduces galvanic effects between alumimium and stainless to 2% – impressive! Other aspects are also mentioned such as, slightly enlarging the holes in the head, anti-corrosive painting inside the holes, and use of Halfords “Bars Leak” in the water. Ken Lack recommended “Fernox” for crystal clear water on opening the drain tap.
I have not personally implemented these recommendations – apart from buying stainless studs from the new Spares sec, which do not appear to be plated. It just goes to show how hard-won knowledge can be lost in the passage of time so that newcomers have to start over again, trying to re-invent the wheel.
Deleted UserThe resistance method sounds very interesting and I must investigate it further. However I had two heads firmly attached to their studs that I put in diesel for about 2 months and then started to consider how to get the two elements separated. T got a pice of steel plate 38mm thick and ground both sides. In this I put four holes for retaining bolts to go into the barrel.
On bore centres, I tapped two M16 holes and made two M16 threaded rods x 200 long with nuts welded to the bottom end and 118 degree taper at the top.
I then made two large cylindical black nylon bungs that had their tops radius turned to match the inside contour of the combustion chamber.
Lastly I made two steel inserts to fit in the underside of the nylon thrust pistons to spread the effort from the M16 stud to the thrust pistons.
You can imagine that this was neither cheap in time or materials. I reasoned that reducing the bond was one thing, but being able to hold the barrel while removing the head without any damage whatsoever, was another. I do accept that it is in my nature to try and devise equipment to make the job more easy, especially if it is likely to be needed again.
The end result was that the two heads lifted evenly from the studs without excessive pressure and with the knowledge that whatever force was applied was applied evenly over a wide area so that any destructive point loading was avoided.
As I said, success so far and I will be pleased to help if other owners have this problem Kind Regards Roger
Deleted UserI am wondering just how effective this resistance heating idea might be despite the claim that it has worked previously.
Firstly let us consider the limits in such an exercise; the melting point of aluminium is about 660°C and as we don’t particularly want to melt the aluminium let us establish for arguement an absolute, (and optimistic), upper temperature of 500°C for this operation. The danger is that at these temperatures even modern aluminium is pretty fragile and the technology has moved on a lot since Scott castings were made, some of which are, shall we say, a bit “iffy”? In fairness it ‘aint that long ago that aluminium was a rare and expensive, even precious, metal which is why some medals were once made of it as was the statue of Eros in Piccadilly Circus.
At 500°C a steel stud will increase its diameter by about 0.002” and the aluminium hole by about 0.004”. The axial elongation of the stud will also help loosen the “grip” but it is the difference in expansion that will break the “grab” and that will still be only 0.006”/inch even though the stud overall will elongate by maybe 0.020”
Now that might be enough but there is still the question of the current required, something in excess of a continuous 300A by my estimation, so how many of you have access to a wopping big welder?
Finally there is the amount of preparation that will be needed if there is to be any reasonable expectation of success. Witness the amount of work Roger has described with his previously mentioned successful pressure method. Preparation, like genius, should not be underestimated; it also consists of 90% perspiration! And usually takes at least twice as long as you think it will into the bargain!
On balance I still consider that cutting the studs through the head gasket joint and dealing with them one by one is the safer and overall quicker method.
Deleted UserMmm. I question the assumptions made here. Firstly that the alloy head will be at or near the stud temperature. The welder current flows through the stud and block – how rapidly does it reach bright red? What transfer of heat takes place, in the time available, into the head which is itself a large heat source and a good conducter? So is it correct to just look at the differential expansion rates – if that were true then the head and its corrosion products would expand away from the stud without any pressure and close back onto it with cooling.
Secondly, is it reasonable to imply that Doug Kephart’s detailed report amounts to just a doubtful claim? He did do it and unscrewed all the studs. If not then what would have been the the point of his articles?
And rather little preparation in fact. No soaking in diesel for months for a start.
Cutting through the studs as recommended aint so simple either. If a milling cutter does the job for the peripheral studs what about the inner ones? A band saw runs the risk of damage. And you also end up having to get the studs out, by drilling and tapping presumably.
Doug Kephart’s engineering knowledge and experience is second to none, as any reading of his many articles about his Douglas and Scott bikes would confirm. He got a bit of similar stick from doubters before when he first published his rebuilding – a – Brum series in Yowl. Nobody said they had tried the welder trick and found it didn’t work.
Deleted UserI am appalled that anyone should think I was casting aspersions, why, I’d not even heard the name Doug Kephart until I read it here! I have no reason to doubt his expertise or the accuracy of his report; my thoughts are based purely on what appears on this site.
The devil lies in the detail, just as it takes 10 or more people to put one soldier into the field so a successful outcome to a job such as this depends on a lot of incidentals not the least of which is the expertise of the operator. Was the job done on a Scott engine or another machine, what equipment was available and so on? One clue to Doug Kephart’s success is the statement that, “Doug Kephart’s engineering knowledge and experience is second to none.” Well, fair enough, but I too have done a little bit of hands-on engineering as it happens.
To reply to Mike Fennell’s points, I was not assuming that the whole head would be near the stud temperature but for all that aluminium is a darned good conductor and it’s going rob an awful lot of heat from the stud, inevitably it will get very hot locally. The suggestion that the stud might be brought up to “bright red” worries me not a little, bright red is generally accepted to be about 900°C. and at that temperature the aluminium local to the stud is at considerable risk, 900°C. is, after all, half as much again as the melting point of aluminium. I’m not suggesting that the whole head will transform itself into a puddle on the floor but there is a real risk of local damage. And whatever is the case you’d still need an ‘effing big welder!
On the matter of cutting through the studs, yes, I agree, the bandsaw idea is not the best, it was thrown in as a last resort, all quite possible but not one I’d choose if there was an alternative, there is a real risk of damaging both the cylinder and head surfaces even in skilled hands even though I have in the past successfully and accurately sawn through much thicker sections of more difficult materials than a Scott cylinder.
My method of choice still remains the milling machine.
I do not see the centre studs as a particular problem as they only 1½” in from the fore & aft edges of the cylinder casting and 6″ diameter slitting saws are readily available.
And yes, the threaded remains of the studs would require carefully drilling out of the cylinder casting but while requiring care in setting up it ‘aint exactly rocket science although equally its not a job for a wobbly arm and a pistol drill!
It is customary to drill the tapping hole for a thread slightly larger than the theoretical root diameter of the thread, typically to give a 70% thread; this creates a little void at the root of each thread, which is easily discerned as a dark spiral in the hole when the size is just right. It should only be necessary to progressively enlarging the hole in small steps on the first hole until this is seen. The remains of the stud can then be picked out, with a little luck and accurate centring the remains of the thread may even uncoil in its entirety but if not, (more likely), once the first two or three turns are extracted then the careful application of a plug tap of the correct size will loosen the remainder. A little at a time is the order of the day here, don’t get too ambitious, remove all loosened detritus regularly.
The remains of the studs in the cylinder head can best be tackled with the aid of a fly press or something similar. A straight push is required; I don’t think the bench vice is on for this job. Preferably the head will be sat on a flat plate with a clearance hole for the stud to pass through to support and spread the load on the gasket face. This will prevent localised loading and the risk of distortion.
I still think that sacrificing the studs is the safest option, even if the heating method succeeds in loosening all the studs in the head the head still has to be lifted or each stud has to be unscrewed and with all that rubbish in each hole the likelihood is a minefield of troubles whereas the stud cutting method uses safe, tried and tested engineering procedures.
But then lets face it; if this particular job was a doddle we’d not be discussing it here in the first place!
Douglas KephartOh-oh, who is this Doug Kephart and why is he causing so much trouble!
I confess it was I that took an arc welding machine and attacked a poor defenseless Brum. Yes I did it, and yes it did work very well. I did try penetrating oil and warming the head up with a propane torch and letting it cool, to no avail. But that was it as far as preparatory work goes. I had heard of others using the hacksaw method, but even with grinding the set off the teeth I was worried about damage should the blade wander off course. The head gasket looked mighty thin, and it sounded like a very laborious task. I was afraid I would loose patience, rush it, and ruin the job. Hence my thoughts along the lines of the old electric rivet furnaces.
The reason Mike that you may not have been able to find the original reference in the Yowl is that was a quite a while ago, Vol.17: No.5, August 1991 (good grief time flies!) Second, it was buried in the middle of a three part and never finished saga on restoring my Brum. It was not an article specifically on the topic of removing stuck head studs.
Mike PM-ed me querying about the original article, and I gave him a summary of the technique and results, but I have to confess I did not check back on the forum till now (another PM) to see what came of it. Only to find I seem to have gone ‘missing’! The three Brum restoration articles and violence with an arc welder are copied in the Technicalities 9.2.18, general restoration topics.
Now to address some of the points raised, particularly the concern about melting the surrounding aluminum. There are a couple of reasons that explain why this does not happen. The stud (if stuck) is surrounded by aluminum oxide, which is a fair electrical and thermal insulator. When confronted with that route or a nice direct path down the stud and into the cast iron block, the current takes- well- the path of least resistance. But probably the main reason the alloy does not get hot, is that there just is not enough time. As I recall it took twenty seconds at most to turn the stud incandescent. No doubt some of the alloy immediately around the stud gets hot, but it does not get near melting temperature. The rest of the aluminum surrounding it is a fairly effective heat sink and the heat transfer from the stud through the aluminum oxide is poor.
I was using a 250amp arc welder. An industrial model, but since I was only using it for twenty seconds at a time, duty cycle rating did not factor in to it. I did not experiment as to how little current it took; I had 250amps on the dial, so of course I set it to maximum! The result was zero to glowing red in twenty seconds. Based on that I do not believe you need 300amps, but that would heat the stud up much quicker. I could not say what the minimum amperage required would be. If you only had say a small 125amp hobby welding machine, then it might take too long to bring the stud up to heat. The aluminum will then have a chance to heat up and expand with the stud. That still might break the corrosive bond and so enable the stud to be removed. In either case axial elongation as the stud heats up will help break the grip of the corrosion. But I think most of the gain was through rapid expansion of the stud and compaction the aluminum oxide. Then as the stud cooled, it pulled away from the surface of the hole. When I finished with a stuck stud, it actually had a slight amount of clearance in the hole; the stud backed out freely. There was a hard ‘skin’ of discolored oxide in the hole, backed up by a softer, powdery oxide. Nor were the threads stuck in the block.
Worst case is if the resistance heating was too slow, you could have time to transfer enough heat from the stud to the aluminum to melt it. But I think this would be rather difficult to achieve because of the thermal conductivity of the surrounding aluminum pulling the heat away. You would have to heat the aluminum through to the water passage right up to the melting point to get it to sag, else it has no where to go, even if the material right next to the stud did start to get a little ‘soft’. One could fill the water passages with water if it is a concern, but it may be easier to find a larger welding machine and get the job done quickly, or use the saw method. It would be a different story if the current were flowing through the aluminum. Remove the cylinder head nuts so that you do not accidentally create a circuit through the head.
One point made in the original article, but not here on this forum, is to make sure that the cylinder block is well grounded. Trying to pass 250amps through too small a contact area will cause arcing. This happened to me, and it burnt a small chunk out of the cylinder skirt. Making sure the skirts were sitting flat on the steel work table (which was grounded to the welding machine) seemed to be sufficient to stop the arcing. I did not have to go to the trouble to find a place to clip the ground cable to on the block, or make a special grounding lug to bolt on.
This method has come up before on the forum in 2004 in John E. Smith’s post of 15Jun04; re- his stuck head on his 1949 Flying Squirrel, where I have a follow-up reply. I think it was in the preceding post referenced, wherein incredulity to resistance heating was aired. I am pretty sure I responded to that and outlined the method used. I could not find that specific post, but note the date mentioned of 16Apr04 seems to just predate the oldest post on this forum, so it must be on the old forum prior to implementing registration. There use to be a link to the old forum, as a sort of archives, but I do not see that now.
I hope this clarifies the method that I used. It is not a method for everyone due to equipment or nerve, but it did actually work. Once…
-Doug
P.S. “metalastic bush”
Deleted UserHmmm! Still got reservations!
I agree, firstly you’ve got to have the nous* and the equipment, to even contemplate going down this route. Let’s face it, there are people that are adequate mechanics, there are a lot more who have five thick stubby thumbs on each hand and then there are the few that have that special “feel” for the game. It seems pretty clear that Douglas Kephart falls into the latter category, his was a clever bit of lateral thinking that worked.
But if you are not totally confident in your abilities and equipment just don’t go there!
The points about the possibility of the oxide layer forming a thermal barrier and the conduction path is fair enough but my reservation here is that the conditions inside the holes cannot be known with any certainty and thus cannot be relied upon.
By the way, given that the job succeeded with about 250A I don’t think my first order guesstimate of 300 amps was too bad!
Douglas says there is no risk of locally melting the aluminium, well fair enough, maybe not in his hands but there would be a lot of heat going in and I still see risks. The comment about damage by arc burning and his stricture about really good earthing is to be taken seriously.
Another point, some of the castings I’ve got are a bit flaky, a lot were made at a time when the metallurgy was in its infancy and seem rather soft with a bit of porosity. Also I’ve heard that the factory was almost always impoverished and you can bet the bean counters had an eye to cost over the best alloy for the job, not the best starting point and these castings are not getting any younger either!
I’ve pointed it out before, aluminium is an extremely reactive metal, (Space Shuttle booster rocket fuel and thermite welding of railway track come to mind); the only reason that it doesn’t normally burn like magnesium and stays nice ‘n shiny is the almost instant thin impervious oxide skin that forms. There are other factors too, so all in all and notwithstanding Douglas’ success; I just don’t see the need to take the risk when there is an alternative.
Anyway, after brutalising the studs in this way I’d not want to use them again for anything other than a pattern so they are still my candiate for sacrifice.
Oh! Yuss! For them wot don’t know their proper English ‘ow she is spoke:-
*Nous /nowss/ n. Brit. colloq. Intelligent perception; common sense; gumption. He! He!
Deleted UserI am very pleased that my prodding has aroused Doug Kephart sufficiently to decide to stick his neck out again on this topic. In my opinion Doug it’s definitely in the wider interest, and how much better to get it from the horses mouth than relying on my failing memory, especially now you have told us that it all took place 18 years ago!
I feel also that I owe efr215 an apology for assuming that everybody in the SOC knows of Doug Kephart and has read his stuff. Obviously not. And I accept that his theoretical calculations were accurate and interesting.
So, where does the average owner, confronted by the problem in 2008, now stand?
Firstly, putting the cart before the horse, I suggest that the old studs should be discarded even if they can be backed out successfully. Reason is, they should all be replaced with plated stainless to reduce future electro-galvanic corrosion. I guess that should include plated washers as well? Then follow the other protective measures in Technicalities 2.4.30
Coming back to the crucial issue though, is it efr215’s cool, careful milling, drilling and defragmentation, or go for broke with DK’s hot, fast blast? In the end it’s probably a matter of temperament. Personally I’m attracted to the DK method but even if you gave me a brand new 250A arcwelder to play with I wouldn’t have the guts to even turn it on, such is my ignorance of those things.
As it happens, I do have a seized head awaiting attention, so I intend to look for an experienced welder with enough nous and adventurous spirit to give it a try. If I find the right man ( and I have an unsuspecting victim in mind ) I’ll document the whole thing and publish it in Yowl and the Forum.
Deleted UserMmm, reading all this I am glad I only have blind head Scotts…
But interesting all the same!
