Drum brake skimming?

[T i m]

Hi all,

No, this isn't a new thing like stone skimming. ;-)

I'm in the process of trying to tidy up (for the potential SonIL) what was probably a fairly expensive 'Peak' trailer that has unfortunately been left standing out in the elements for a good few years.

Yesterday we collected it, got it home and have now stripped it down and whilst some of the sights were pretty grim, after a once over with a wire brush and a quick squirt of Plus-Gas to get things moving it seems salvageable (especially when you see the s/h price of 1 tonne goods trailers). The actual chassis is galvanised so seems unmarked.

So, I'm trying to work out some rough costs before we commit too much and the first thing that could work out expensive is the brake drums are pretty grim and new are quite expensive (£100+ / pair). So I wondered if anyone knew roughly how much it might cost to get them skimmed (it's only to remove the rust / scale from the actual braking surface), or is there a d-i-y solution by using one of those expanding

3 legged hones you can put in an electric drill maybe?

This is only a trailer (as opposed to a performance car and no I won't skimp of brakes etc whatever it's on, but ..) and the doesn't seem to be much wear to the drum (the shoes look new and show contact all over the surface) and I'm guessing they might self clean to some degree in use in any case?

If anyone knows a friendly engineering shop or retired engineer with the facilities to give these a quick once over for me please I would be pleased to know (ideally Nth London / Herts / Essex etc as they would be quite heavy to post).

All the best and thanks for your time etc.

T i m

p.s. They are a bit too big to fit in my Myford ML10. ;-(

[Gary]

Why not just clean then with a bit of wet and dry. the surface shurly will settle down with use and they are not distorted?

just a thought. Gary

[T i m]

Hmm, I could give it a go I guess. Can't see it doing any harm as long as I keep it all uniform etc.

That was my thought (that they might 'settle down') and from experience of the braked trailer I built over 30 years ago (where like many cast iron brakes rust up a bit if used infrequently than can 'grab' for the first time they are used)

And a good one. ;-)

I did run some of that fairly coarse yellow paper (comes in a roll, seems pretty durable) over one drum as a test and it did feel like I was getting down to the metal but as it still looked a bit pockmarked I considered the skimming option.

Cheers, T i m

[NT]

A bit pockmarked doesnt matter. What matters is to get the lumps of crud off the surface so the brakes wont lock up in use. It should be possible to do that with sandpaper, I'd resist the temptation to get the surface spotless, as doing so would inevitably take it out of round very slightly, which would impede performance for a while. Rust etc will come off a lot easier in use on the road than solid metal.

FWIW there are some fairly evil experiences to be had pulling trailers, I'd make sure he's familiar with the things limits before using it in anger.

NT

[Dave Plowman (News)]

Just take the rust off by your usual means. The shoes will soon clean them up. You only need to skim if they are oval.

[Matty F]

Angle grinder with a flap disk. Someone rotates the drum while you use the angle grinder.

Now that I have a lathe I would put the drum in there and turn it smooth.

[Paul - xxx]

As has been said, clean as much crap off and out as you can and get them in use, the shoes will do the rest. I'd syggest a 10 mile round trip with lots of braking points ..

Then take them off and clean 'em up again, it's likely there'll be a lot of s**te in them again .. :)

[T i m]

Oh, ok. I guess if the edges of the holes are smooth it wouldn't abrade the shoe lining particularly (ie, not like a cheese grater).

Understood. Strangely the rust that is on most of the inside of the drums looks very bad but mostly seems to brush off quite easily?

Of course as most of the stuff is cast iron or stamped steel and inside the drum it doesn't matter what it looks like as long as it woks ok. ;-)

After the easily-removed surface / loose rust there seems to be a particularly had 'skin on the actual frictionable surface of the drum, more so than anywhere else. Possibly because it was clean / bare metal at some point in it's life (the trailer was actually stored on one side at some point so the lower hub will have been full of water and possibly for a considerable time). That said everything was moving again pretty quickly / easily and I've had much much worse from less 'bad' circumstances (maybe begin immersed in water is less bad that being wet / dry / wet / dry etc)?

Understood.

Understood. FWIW he comes from rural Scotland and is of a agricultural / horticultural / tree surgery background so (luckily) is familiar with all sorts of (often nasty) machines and devices. However, he does still need to take his trailer test to be able to tow bigger than

750kg on the road.

This trailer was last used to carry a diesel 'jetter' and a couple of water tanks so is 'very solid'. I was initially tempted to reduce it's with to that of a more typical car or his Hi-Lux truck so as to minimise the issues with having a trailer wider than the towing vehicle (if only by 5" each side as in this case) but the effort in doing so would be less than this 'issues' (and advantages of it re carrying volume) of it being a bit wider so I'll leave it for now at least.

As it's basically a flat grid, for speed and convenience I was thinking of just making up an 8' long angle 'sub-frame' to turn it into a 8' [1] x ~5' x ~3' goods / box with drop down tailgate. He wants it to be a tipper but he can dream on for now. ;-)

Cheers, T i m

[1] Ply easier to get in 8' lengths. ;-)

[T i m]

Hmmm, I like the idea but I'm not sure there is quite enough room between the bearing hub and the inner drum face for such (it's more like the newer rear drums on a car where you have to undo the bearing to get it off, rather than the drum just sitting on the end of a halfshaft etc).

Oooh, where do you live! ;-)

Cheers, T i m

[T i m]

How practical is a home shot / bead blasting booth do you think Dave? I think I'd put one alongside my parts washer, angle grinder, lathe and MIG these days.

I have a 50l 15 cfm compressor if that might work in a mini slow-but-sure-and-it-works kinda way?

Ok thanks. I wasn't sure if doing such would be considered 'bad practice' (but I guess that could depend on 'how bad' the rust was and the application etc).

Well, whilst I haven't checked for that (I was going to once I'd got them a bit tidier) it doesn't look like they have had that much use (no real obvious lips etc).

Cheers, T i m

[T i m]

Yup, been there, done that. ;-)

Good tip, ta.

Cheers, T i m

p.s. the 1/2 ton (it wasn't tonnes then) braked (Morris minor brake parts) trailer I built 20 years ago doesn't have a damped brake coupling so when the trailer hadn't been used for a while and especially when it was empty you did need a few 'test brake sessions' to get the overrun part to work smoothly again. Once the sharpness had been knocked off the brakes it was (is) one of those well behaved trailers that just sits there [1] and you can generally forget about (as it was generally no wider than most of our vehicles). As is the trailer I tow behind my BMW motorbike ... it's 50mm narrower than the touring panniers. ;-)

[1] I still have a couple of the Indespension (I think it was) rubber mounted tow balls so you don't even hear much in the way of coupling noise from the trailer either.

[fred]

In article , T i m writes

A small cup shaped wire brush in a drill would be my first port of call, then cleaning up by running the trailer around the block with the brakes just rubbing (manual adjust?). Knock off any stubborn pips with an old screwdriver.

Something slightly larger than this but you get the idea:

[Paul - xxx]

Might be worth also checking the shoes again, the cost of a new pair shouldn't be too extravagant .. ;)

Nice .. ;)

[Dave Liquorice]

Sounds to me as if they have cleaned up reasonably well with a bit of abrasive paper. A bit of soft rust isn't normally a problem in brakes first few uses cleans 'em up if looking at how quickly discs rust up these days.

Be worth checking that they are within tolerenace of being round.

[The Natural Philosopher]

Or deeply scored

BUT its almost not allowed these days. Reduces thermal mass and so brakes get hotter.

[dennis]

What rubbish.. they will not get significantly hotter (at best they will heat up quicker by a fraction of a second). The reason you can't skim them these days is that there isn't enough metal left to do it. They have already cost/weight reduced them to the limit when new.

If its a really old bit of kit off a minor I wouldn't be surprised if you could skim a mm off them.

[Dave Plowman (News)]

It would be nice to have - but not needed for this. A wire brush will do fine - the shoes will do the rest.

Discs especially rust up quite quickly when not used. The lining material is hard enough to soon remove it. But with drums, a clean out after a short amount of use would be a good idea.

[Dave Plowman (News)]

Doesn't seem to effect their performance in practice.

Discs often have a minimum thickness marked on them. Not seen this with drums.

[MuddyMike]

I used a flapper wheel sanding tool in an electric drill for cleaning the drums on an old (1953) Sankey trailer I bought that had stood idle for many years. Never had a problem with the brakes once they settled in and I got them properly balanced.

Mike

[The Other Mike]

Ones from the 80's and 90's often do.