question Disc Brake resurfacing

[fesm_ndt]

Curious if anyone has heard of any company that re-surfaces disc brakes?

 

When I say re-surface I am not talking skimming I am talking about putting a layer of weld on the increase the thickness of the original disc then machined flat?

 

I have seen metal spray, weld overlays and other more fancy stuff in my line of work so I cannot see why it can't be done. Just haven't found a link to it.

[oily]

Probably because it'd be cheaper to buy new discs, or have new ones made, or existing similar ones modified/machined to suit....

[fesm_ndt]

Probably because it'd be cheaper to buy new discs, or have new ones made, or existing similar ones modified/machined to suit....

 

yeah I thought the same thing, but also thought there must be some rarer discs out there ie the Pinzgauer discs are specific. I have heard of no other disc that fits.

[robin craig]

Mike,

 

You have me somewhat caught off guard by your question.

 

The act of spray welding would still require some machining afterwards and even then one would have to spray weld both sides at the same time otherwise warpage would occur but seeing as how you are familiar with welding processes I think you have to agree the economics would be beyond what it would cost to produce new rotors.

 

Are they that scarce or are you just a bit short of a quid or two mate? (meant in the best possible way)

 

R

[Stormin]

From what I undertsand brake disc are usually cast iron.

Welding to cast iron is not a simple process, usually involves pre-heating. Preventing warping and cracking could be an issue. Obviously will need to be machined afterwards.

 

Probably easier to just get new ones cast from a pattern. If you make or have the pattern made and keep it, getting a batch done every now and again, I'm sure there would be market for Pinz replacement discs.

[zoltan]

The ramifications of a failure in any coating onto cast iron with the thermal cycling that discs see don't bear thinking about. Pound to a penny this will be downhill full load etc etc :shocked:

 

From a liability perspective I'd be surprised if you found a company who would undertake this

 

As a safe alternative you could consider getting a aluminium bells made and fit flat disc rotors to these thus making replacement in the future a great deal cheaper. There are plenty of vented and solid flat discs available from motorsport brakes manufacturers such as AP Racing

[fesm_ndt]

Probably because it'd be cheaper to buy new discs, or have new ones made, or existing similar ones modified/machined to suit....

 

I think this is the most likely reason no-one is doing it i.e. most vehicles with disc brakes are newish so not so scarce. Also there is a lot of compatability is most vehicles.

 

Mike,

 

Are they that scarce or are you just a bit short of a quid or two mate? (meant in the best possible way)

 

R

 

Apparently they are hard to come by. I have plenty of spares so the question is academic on if anyone had heard about it. I do work for a living and never had a silver spoon, so I do tend to look for alternatives.

 

The ramifications of a failure in any coating onto cast iron with the thermal cycling that discs see don't bear thinking about. Pound to a penny this will be downhill full load etc etc :shocked:

 

From a liability perspective I'd be surprised if you found a company who would undertake this

 

As a safe alternative you could consider getting a aluminium bells made and fit flat disc rotors to these thus making replacement in the future a great deal cheaper. There are plenty of vented and solid flat discs available from motorsport brakes manufacturers such as AP Racing

 

I really don't concern myself about liability as I work with insurance companies doing investigations and there is no liability if done correctly.

 

Distortion in welding is caused by poor parameters and technique, not welding. For example the surface could be TIG (GTAW) welded with very little distortion or damage to the parent metal or HAZ (Heat Affected Zone). However as Robin said the effort would cost a lot as TIG (GTAW) is quite slow. There is robotic TIG (GTAW) but goes up a notch in price again.

 

The reason I was wondering:

 

- I have seen large steam valve butterflies weld overlaid basically using a rotating device and an automatically fed GMAW system similar to BUGO system. The weld overlay is far more resistant to abrasion than the stock item.

 

- I saw several websites saying they resurface but in reality they are skimming which is not that great in full floating disc brakes as at a certain point the pads can fall out.

 

I guess in the end the best solution if they become completely unobtainable is to machine them up out of some billet material like Porsche high performance discs

[robin craig]

Mike,

 

I would tend to side with Stormin Norman that considering the labour prices and dare I say it the proximity to China that re casting them and machining sounds like an option that would be cheaper than trying to rebuild them by any process.

 

You might even turn a profit

 

Try not to grimace as you read this

 

R

[fesm_ndt]

CHINA :banghead:!!!!!!!!!!

 

was just reading a post about adjustable shock absorbers, made in the USA but really made in China. Not suprisingly they had zero quality, actually zero would be an upgrade.

 

ahh I been living here too long ......... CHINA, talk about welding with no rules

 

I had to buy a welding mask for the guy who does my welding as he welds with no mask, just blinks a lot (pretty common). I got a picture somewhere of a guy using 2 rods at once, one in each hand. Thought he was pretty clever but wasnt really following procedure so ended up with 3m long cracks which was some concern as was on the worlds tallest building at the time.

 

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[steveo578]

those are the funniest photos I've seen in along time:-D brilliant

[griff66]

bloody hell poor buggers

[zoltan]

I think this is the most likely reason no-one is doing it i.e. most vehicles with disc brakes are newish so not so scarce. Also there is a lot of compatability is most vehicles.

 

 

It is more likely that it is potentially very dangerous. There is a very real risk of failure under load. Cast iron discs have enough of a hard time with the continuous heat cycling in use without other imposed thermal stresses and variations in friction caused by the addition of other materials. Assuming you found someone brave or foolish to undertake the work I would expect you will have pretty severe juddering problems when the discs get hot. There will also be a very high probability of cracking from differential expansion of the CI and the filler/weld material

 

 

 

I really don't concern myself about liability as I work with insurance companies doing investigations and there is no liability if done correctly.

 

I was thinking more from the perspective of the person doing the work for you. I make brake discs from castings (amongst other things) and would certainly not undertake this kind of work for any customer.

 

 

 

I guess in the end the best solution if they become completely unobtainable is to machine them up out of some billet material like Porsche high performance discs

I don't know the Pinzgauer discs, are they a solid or vented disc?

[fesm_ndt]

 

I don't know the Pinzgauer discs, are they a solid or vented disc?

 

They are solid which is a mystery, so a machined up set is feasible.

 

Welding is feasible, or a welding technique is feasible as there are suitable techniques, so damaging the material or failing under load is not an issue as I deal with all types of welding so I have zero doubt it is not feasible. I work for a welding research company.

 

Just seems there is no need in the mainsteam as the steam valve butterfly repair would be under more severe stresses than brakes and the welding technique was not difficult but the welding wire was fancy. There are several automated repair techniques like this in the petrochemical and power sectors.

 

Some things are just Pinz specific, discs, rear shock absorbers and tie rods (why they would make specific tie rods baffle me).

[fesm_ndt]

bloody hell poor buggers

 

In some cases this is true as the imported workers can get treated like slaves. An incident that sticks in my memory was the bus stands needed repainting in a particuliar city.

 

Solution = get workers give them buckets of paint and rags. To paint the bus stands they had to soak the rags in paint and wipe the paint on.

 

Result was they had paint all over themselves. At the time I could not believe they would not buy cheap paint brushes.

 

Another incident was when we got extentions done at the welding school the contractor was welding some bits with no mask. I got a bit worried about this as we are meant to be the welding people so I got him a mask and he refused to use it. I can'y understand why they are not completely blind as I hate it when I get an inadverdant arc flash.

 

I will see if my welder today will wear his mask as I bought him an auto one

[andym]

Another incident was when we got extentions done at the welding school the contractor was welding some bits with no mask. I got a bit worried about this as we are meant to be the welding people so I got him a mask and he refused to use it. I can'y understand why they are not completely blind as I hate it when I get an inadverdant arc flash.

 

I will see if my welder today will wear his mask as I bought him an auto one

 

Methinks that reading the Health and Safety at Work Act might be useful, especially understanding the obligations of employer and employee. And I think we've wandered off-topic somewhat!

 

Andy

Edited September 20, 2010 by andym

[fesm_ndt]

Methinks that reading the Health and Safety at Work Act might be useful, especially understanding the obligations of employer and employee. And I think we've wandered off-topic somewhat!

 

Andy

 

Why would I want to read UK regulations in Malaysia?

 

The SHE armchair crowd can KMA as I don't live in a country where people want free payouts for spilling their mCDonalds coffee.

[andym]

Why would I want to read UK regulations in Malaysia?

 

Good point - I'll pay more attention next time! :embarrassed:

 

Andy

[fesm_ndt]

No worries. I got nothing against SHE but western countries have screwed themselves with frivolous cases.

 

We had a recent one in Australia where a guy in a bar took out a lightbulb and stuck his finger in there with obvious results. He sued the bar and won a payout because the judge said he should not have been able to do it. These costs get tacked onto everything else.

 

Anyway my guy used his new welding mask and I ended up with the arc eye

[gritineye]

Just a thought, but presuming the metal spraying/welding/machining works OK, isn't the next thing to worry about the coefficient of friction of the new surface compared to the parent cast iron, and then matching the pad friction material to that?

 

As the surface wears down near the parent metal, through the join area and so on the braking performance would surely change..

[fesm_ndt]

Just a thought, but presuming the metal spraying/welding/machining works OK, isn't the next thing to worry about the coefficient of friction of the new surface compared to the parent cast iron, and then matching the pad friction material to that?

 

As the surface wears down near the parent metal, through the join area and so on the braking performance would surely change..

 

That is most likely an interesting point as the hardfacing I seen is definately harder. One type I seen looks porous as the little holes help disapate the heat.

 

Anyway is good to get several heads looking at it from different angles. Just thinking on the comments I guess drums are the same issue but for another academic question....... Do they make these from cast iron for purpose or costV ie a milled item from a big chunk could be made but lots of material wasted

[Stormin]

That is most likely an interesting point as the hardfacing I seen is definately harder. One type I seen looks porous as the little holes help disapate the heat.

 

Anyway is good to get several heads looking at it from different angles. Just thinking on the comments I guess drums are the same issue but for another academic question....... Do they make these from cast iron for purpose or costV ie a milled item from a big chunk could be made but lots of material wasted

 

Drums are cast as well. As you summise much cheaper to machine from something that's near the right shape to start with. Cast iron must have the right sort of properties as it's been used for brake friction surfaces for hundreds of years. One advantage above steel is it's not as prone to rust.

[sirhc]

We often salvage mis-machined and worn parts using these coatings, including parts made from cast iron such as bearing housings etc. Not sure I'd want to do a brake disc or drum though!

Metco 447NS 10-133.pdf

Metco 450P 10-137.pdf

[fesm_ndt]

We often salvage mis-machined and worn parts using these coatings, including parts made from cast iron such as bearing housings etc. Not sure I'd want to do a brake disc or drum though!

 

Thats interesting stuff, a much more fancy version of what we used to call metal set. I once stupidly used it instead of Bondo filler and was a real problem to sand back. I guess it is quite pricey? We have a diff casing with a divet in the side, would be ideal for that.

 

One advantage above steel is it's not as prone to rust.

 

that's interesting also, I guess its got to do with the second law of thermodynamics.... basically steel requires more energy to create compared to the base state it wants to return to. Cast iron is only a slight notch above so is more stable.

 

been a good topic, welding, safety, bonding, casting

Edited September 20, 2010 by fesm_ndt

[sirhc]

Thats interesting stuff, a much more fancy version of what we used to call metal set. I once stupidly used it instead of Bondo filler and was a real problem to sand back. I guess it is quite pricey? We have a diff casing with a divet in the side, would be ideal for that.

 

 

Yes, the powder is expensive, but nowhere near as expensive as the equipment required to spray it! More info here: http://en.wikipedia.org/wiki/Thermal_spraying#Plasma_spraying

 

Chris

[zoltan]

Yes, the powder is expensive, but nowhere near as expensive as the equipment required to spray it! More info here: http://en.wikipedia.org/wiki/Thermal_spraying#Plasma_spraying

 

Chris

 

I have to confess, having said that coating discs could be dangerous that we used to manufacture aluminum rear brake drums for classic cars with plasma sprayed friction linings and although expensive compared to our competitors who cast steel rings in,ours were pretty reliable and very light.

Too much heat could cause delamination so we only recommended them for the rear. One benefit of the plasma spray was being able to adjust the powder mix to put plenty of copper in and achieve very good heat transfer without lowering friction levels to much

[fesm_ndt]

Yes, the powder is expensive, but nowhere near as expensive as the equipment required to spray it! More info here: http://en.wikipedia.org/wiki/Thermal_spraying#Plasma_spraying

 

Chris

 

Ok I just skimmed it and saw the bonding bit. The mob I worked for has a lot to do with inventing these weird welding techniques. Interesting to see something like hollow turbine blades weld repaired both sides one pass from one side with electron beam.

 

http://www.twi.co.uk/portfolio?playlist=pl_laser

 

http://www.twi.co.uk/portfolio?playlist=pl_friction

 

http://www.twi.co.uk/portfolio?playlist=pl_resistance

 

http://www.twi.co.uk/portfolio?playlist=pl_arc_welding

 

 

didnt know these were online just now

Edited September 21, 2010 by fesm_ndt
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