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Post by gingerneer on Aug 27, 2014 8:21:32 GMT
Hi Guys
What are my options for repairing a chip in the flange of a driving wheel?
I know the belt and braces way is shrink fitting a steel tire. I am a bit hesitant to do this as the wheel set in question have inside cranks built up with Locite, and i am worried that any application of heat will break the bound.
Is is possible to repair the chip by grafting a piece of material in place. I have been looking at the likes of JB weld and plastic metal which if given a good key should be strong, the flange profile could then be cleaned up.
Any thoughts would be welcome.
Will
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Post by houstonceng on Aug 27, 2014 9:04:58 GMT
If you wrap the cranks in a wet cloth, the temperature shouldn't kill the Loctite bond. You'll be heating the new tyre, not the wheel.
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jma1009
Elder Statesman
Posts: 5,900
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Post by jma1009 on Aug 27, 2014 9:20:41 GMT
hi will,
i think it all depends how bad the chip is, and how big/long, and whether the loco is to be used only on a raised track or on a groundlevel track with points. it is possible to use a variation of the type of repair used by clockmakers if a cog loses a tooth, ie cut a notch in the flange and fit a new piece of steel into the cast iron flange. clean repeatedly with loctite cleaner or cellulose thinners beforehand so the joint is as clean as possible before loctiting into position.
the flanges on a driving wheel should have less pressure on them than say the leading wheels.
there is no reason why a new tyre shouldnt be loctited on rather than shrink fitted, but i think you would have to extremely careful putting a crankaxle between centres to turn down the wheels for fitting steel tyres.
cheers,
julian
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Post by Deleted on Aug 27, 2014 9:50:38 GMT
Hi Will, The Kingette I rebuilt had a repair to a flange done in a similay way to that Julian describes. A slot was cut in the back of the tread and a piece fitted in and held with a countersink screw. Whoever did it (not me) made a very neat job of it.  People have successfully silver soldered pieces in but cast iron is not the easiest stuff to silver solder. A screw and Loctite should be plenty strong enough. John |
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Post by ettingtonliam on Aug 27, 2014 10:59:50 GMT
Yes, that piece let in looks as if its dovetailed, so if thats a good fit, plus the screw, it won't shift.
Richard
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Post by gingerneer on Aug 27, 2014 13:59:14 GMT
Hi Guys
Thanks for the reply's
The wheel set in question is for a 5" Mabel (LBSC's take on a LNWR Jumbo). I have no photos with me at the moment of the damage to the flange. While i was hoping for a quick fix i think its going to be strip down job. After looking over the chassis one of the many niggles i have found are 2 of the wheel sets are out on the back to backs dimension. One of the wheel sets being the main crank axle. While i would be mainly using the loco on a raised track i would like the option of using it on a ground level, so the wheel dimensions are a lot more critical, the flanges would be under more stress going through point work.
So strip down and steel tires to be fitted.
What steel spec is best to use for tires, and were could i obtain some from?
With the fitting of the tire by Locite would you pin it as well?
Any comments welcome
Will
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Post by daveburrage on Aug 27, 2014 20:09:27 GMT
A friends engine, a 7 1/4 Black Five, had a large chip takem out of a wheel flange after de-railing. I got it welded up (you can weld CI with right rods and procedures). Its worked ok ever since.
It wasn't even trued on a lathe - just carefully hand ground.
regards
Dave Burrage
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61962
Seasoned Member
Posts: 129 
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Post by 61962 on Aug 27, 2014 22:54:45 GMT
Will,
I'm just in the process of putting tyres on my 3 1/2" gauge GNR Atlantic to rectify a chipped flange on a coupled wheel. I'm doing all four because the loco has done a lot of running and the flanges are getting thin. I've had the tyres made in EN8 which will give excellent resistance to wear, although I don't expect them to wear out before I do. I have done this before on single wheels and can't say I've had any problems. I make the interference 1 thou per inch plus a thou. Wrapping your axle in wet cloths should be sufficient protection for the Loctite in the crank, especially if you quench the tyre as soon as it has gripped the wheel. I'd be more concerned about the glued joints when you are turning the wheels. If you can get the axle into the lathe with the wheel you are turning next to the faceplate then that will solve the problem. Make sure you put accurately dimensioned spacers between the crank webs before putting the axle between centres.
I did once fix a chipped flange by putting a series of steel studs in the space, dressing them off to match the profile and filling between with plastic metal. The wheel is still in service, although the plastic metal has long disappeared.
Best of luck
Eddie
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Post by Roger on Aug 27, 2014 23:03:02 GMT
If you fit steel tyres, be sure to rough them somewhere near to the final size before you shrink them on because you don't want to remove any more material than absolutely necessary when they are turned on the axles.
Just a thought on the plastic metal route... you can buy Titanium Putty in the Devcon range and that's incredibly tough compared to the Aluminium loaded normal variety. I've made up bearing journals with that stuff to reclaim shafts where ball races have fretted on the shaft. You'd have to use a tipped tool to machine it or a Dremel though, it's very hard.
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Post by chris vine on Aug 28, 2014 9:18:18 GMT
If the crank axle is bonded with loctite, there is no need to do anything stronger for the tyres. There is much more area for loctite to grip and the forces are much less, so it will be much less stressed than the crank parts.
Chris.
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61962
Seasoned Member
Posts: 129
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Post by 61962 on Aug 28, 2014 21:56:18 GMT
If you fit steel tyres, be sure to rough them somewhere near to the final size before you shrink them on because you don't want to remove any more material than absolutely necessary when they are turned on the axles. Roger, The tyres are machined to finished dimensions before fitting. The wheels are machined on the axles between centres to suit the tyres so there is no need to finish machine the tyres in-situ. Eddie |
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Post by Roger on Aug 28, 2014 22:13:05 GMT
Ah, I see. I just thought it would be easier to get the back to back distance and runout right if it was done on the axle.
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jma1009
Elder Statesman
Posts: 5,900
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Post by jma1009 on Aug 28, 2014 22:28:08 GMT
hi Eddie,
werent tyres finish turned on the axles after fitting?
ive watched BR wheelsets turned on a 100 year old wheel turning lathe in Ryde Works on the IOW, and modern tyre turning machines in more modern mainline workshops where the wheelsets stay on the train.
cheers,
julian
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61962
Seasoned Member
Posts: 129
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Post by 61962 on Aug 28, 2014 22:47:40 GMT
If the crank axle is bonded with loctite, there is no need to do anything stronger for the tyres. There is much more area for loctite to grip and the forces are much less, so it will be much less stressed than the crank parts. Chris. Chris, Whilst I understand that Loctite is an excellent bonding agent and that many people have great faith in it's properties, I'm afraid my experience with both built up cranks and Loctite make me avoid using Loctite for crankshafts. I have silver soldered, brazed and press fitted crank axles over the years and the only certain method I have found is to use substantial interference fits with keys and dowels to ensure the parts stay together in service. I'm sure someone will tell me that they have successfully used Locitite on loco crank axles, but my experience with Loctiting wheels to axles has usually ended with the joints failing when the axles have been put into the lathe for profiling the wheels, and this has happened to me with locomotive and passenger vehicle wheels and I am concerned that in this circumstance the crank axle will be very vunerable, particularly the crank pin to web joints. It may be that the problem is related to the application of the Loctite. Clearly cleanliness and fit are important considerations as well as the type and the age of the Loctite and I know there are many model engineers who can achieve the exacting standards required to make the joints properly, but all too often Loctite is used as a last resort when press fit tolerances have not been achieved and I therefore recommend that proper press fits and keys are the only way to ensure longevity in model locomotive axles. Loctiting tyres is another issue. The shear stress in the tyre/wheel interface must be very low and the Loctite will do what's necessary in service, but one of the advantages of the shrink fit is the compression the tyre applies to the wheel centre which improves the security of the attachment of the wheel to the axle. Another advantage is that a shrink fitted tyre has built in circumferential stress which is a mitigation of the possibility that the rolling action will cause the tyre to increase in diameter over time and therefore come loose. Eddie |
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Post by Deleted on Aug 28, 2014 23:08:07 GMT
error!!
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Post by Deleted on Aug 28, 2014 23:14:50 GMT
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61962
Seasoned Member
Posts: 129
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Post by 61962 on Aug 28, 2014 23:16:26 GMT
Julian,
I'm pretty sure you are right about new tyres being finish turned on the wheel set on full size locomotives, but I think that may have been due to the ability of the manufacturers to produce a really accurate tyre given that it is quite a flimsy component. In our sizes the tyre is fairly rigid and they can be produced on CNC machines to high accuracy. I do get mine done for me, but I have made them in the past, the most difficult being for a 3.5" gauge Stirling single because it was so easy to distort them whilst being held in the lathe. They were turned in stages clamped to the faceplate and I did do the final profiling after fitting to the axle.
I saw several wheel sets reprofiled when I was a regular volunteer at Carnforth. This was on a traditional wheel lathe and is quite labourious, each pass taking several minutes. One locomotive that came in had very worn tyres with seriously concave treads and undercut flanges and it took days and weeks to get them done at the expense of the full stock of tungsten tool tips in the stores, because the surfaces were so work hardened.
Modern machines do turn the wheels without the need to remove them from the vehicle. The machines I have seen use rotary cutters rather than fixed tools and are very quick.
To answer your comment Roger, the tyres are as I said accurately machined, The wheelset is machined to receive the tyres between centres and the back to back dimension is easily achieved by careful measurement of the overall width over the wheel centres. The tyres do have an outer flange which sits against the wheel face, so by facing the wheels the back to back can be corrected if the original assembly is wrong. I've check my atlantic' wheel sets tonight and the back to back is only about 3 thou out, but there is a slight run out which will disappear when the wheel centres are turned for the tyres.
Eddie
Eddie
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Post by Roger on Aug 28, 2014 23:53:40 GMT
That sounds plenty good enough to me too.
I think the issue with Loctite and axles may be due to two things. I don't know how it adheres to Cast Iron, but my guess is that it's nothing like as good a bond as it is with steel. It's also vital to get every last hint of oil off the surface and that's not easy to do. We used to have to get that kind of cleanliness on Air Bearing spindles and virtually all solvents that you use leave a residue behind. We used to pre-clean with meths and then use an electrical safety solvent and lint free wipes. Only then was it totally free from grease. Touching a surface once it's degreased is an absolute no no. Maybe that sounds over the top, but if you want it to stick to the surface, you have to let it reach the surface if you see what I mean.
The other issue is that you need to leave a very definite undercut for the Loctite to remain in. If you don't, there won't be enough Loctite in the joint to give it any strength. We used the Retaining compound, the one with the blue colour. When it's applied that way on two steel parts, good luck getting it apart!
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dfh
Hi-poster
Posts: 197
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Post by dfh on Aug 29, 2014 9:20:26 GMT
That sounds plenty good enough to me too. I think the issue with Loctite and axles may be due to two things. I don't know how it adheres to Cast Iron, but my guess is that it's nothing like as good a bond as it is with steel. It's also vital to get every last hint of oil off the surface and that's not easy to do. We used to have to get that kind of cleanliness on Air Bearing spindles and virtually all solvents that you use leave a residue behind. We used to pre-clean with meths and then use an electrical safety solvent and lint free wipes. Only then was it totally free from grease. Touching a surface once it's degreased is an absolute no no. Maybe that sounds over the top, but if you want it to stick to the surface, you have to let it reach the surface if you see what I mean. The other issue is that you need to leave a very definite undercut for the Loctite to remain in. If you don't, there won't be enough Loctite in the joint to give it any strength. We used the Retaining compound, the one with the blue colour. When it's applied that way on two steel parts, good luck getting it apart! Loctite 603 is an oil tolerant high strength retainer made for when cleanliness cannot be guaranteed, we used to use it in Witte fluidise bed shaker g/boxes to hold the bearings in cast housings, the g/box had belt driven input shafts at each end and eccentric weights flying around in the middle. Loctite was specified by Witte and was used in new boxes as well as rebuilds, never saw any failures. Don't believe you have to have an undercut to have a good joint, just the recommended clearance or lack of clearance as with a press fit as specified by Henkel, there are irregularites in the materials surface and Loctite fills these, it is a myth that the Loctite is pushed out when used in a pressed fit so no undercut is neccessary. |
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Post by Roger on Aug 29, 2014 11:58:29 GMT
it is a myth that the Loctite is pushed out when used in a pressed fit so no undercut is neccessary. I think this largely depends on the fit. On the sorts of very high precision assembly we used to repair, there was always an undercut for the Loctite and the fits were so close to retain concentricity that there was no visible Loctite on the locating areas. I don't think you'll have much Loctite left in a joint where there's a press fit, although Cast Iron would probably have enough texture in the surface to retain some. I think undercuts are considered by most to be best practice because they take the chance out of the equation. |
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