Scania truck S cams..

[snowcat]

Shot in the dark this, could be a few phone calls to the TWI to find the answers but IL give it a shot here first, The pictures show an Induction hardened S cam off a Scania Truck, at nearly £400 a throw, firm has used 10 in six months OUCH!! the cams are fine but they wear on the shaft, where 2 Phos bronze bushes sit, we think its simply down to road grime/corrosion rather than any great wear issues ocour as the phos remains perfectly in tact...

So the thinking is of a shaft build and machine back, simple except for the fact the materials induction hardned.....

Heres the question,s I need to be able to put about 0.040"+ of filler onto the shaft, It needs to be machinable but still be suitable for the parent material, the material on the shaft does not need to be particular hard (Its only running on phos) but I cant lose the induction harding or temper the material too much in the cut splines or cam end.....

This might be impossible (Ho Hum) but could be a nice little continual refurb job if it is, answers on a postcard please

 

[Drains]

1) have they been in touch with Scania about their crappy short-lived S cams?
2) what does an S cam do?
3) any danger of a weld/machine/case harden on that?
4) where is the grime getting in, and why, and would more regular greasing help?
5) weld with whatever TechnicAl will hopefully suggest ( a 70xx rod, standard mig wire, er.. a stainless????), and draw the heat from the splines with Cold Front

No danger of shrinking a sleeve onto that by the looks.

 

[matt1978]

How about Mig Brazing it Snowy with a Cu Al 8 filler wire??

 

[TAITSIE]

Hi
The pictures show that the wear has been caused by water/dirt ingress
I would change the seals at the same time as the cam and also check that if fitted the autolube system is working ok. I worked on buses for over twenty years and I reckon that 75% of the cams that I fitted had been reworked but I dont know what process had been used

 

[Hitch]

There must be some sort of unerlying problem surely?

Tell them to lay off the middle pedal!

 

[Hitch]

Heres a thought.... Is it on the same one every time, surely not. Is one of the brackets that the bush fits in damaged at all, perhaps putting an awkward load on the shaft?
It looks like the end nearer the splines has taken a bit more wear?

Im not certain oof the setup, but how about adjustment, are they being pushed too far round? Obviously the s end can only go so far, but is the actual actuator trying to push it a bit to far, causing it to wear more than it should?

 

[zzr1200]

Snowcat, I personally wouldn't go near them, the idea of an on going re-occurring job is great, but if something should ever go wrong you don't want VOSA, HSE and legal briefs knocking on your door (and we are talking well loaded 8 wheel tipper brakes here).

I would look around for a supplier of pattern parts there must be a firm producing them somewhere, I would start by contacting:


Industrial Friction Services Ltd.
Unit 1
Manor Road
West Thurrock
Grays
Essex
RM20 4BA

Tel: 01708-864935

One of the best commercial vehicle factors in the area, ask them to find and supply, then become a middle man "buy 'n' supply" is the way to go here, imho.

zzr

 

[snowcat]

Righto, S cam forces the brake shoes on so kinda of an integral part yes scania are aware, but its a greased item, so thats there argument.... saying lube greaser etc is all fine However a fleet of 16 Lorry's, 6 360s, 3 shovels 4 concrete crushers, plus untold other plant, and just two fitters it don't happen, drivers cannot be assed with such dirty work..........You get me point, be great to live in a perfect world, but it ain't gonna get greased as it should

The wear is identical on the 8 or so worn cams I was given, and its around 0.040" oversize when it causes braking issues, also theres no seal, it is only the grease that keeps it alive.

as said we cant soften the splines or cam, or temper or weaken the shaft, but the deposit can be soft....

Open really to any process BTW Matt MIG brazing is something I'm a complete Virgin on tell me more......

 

[matt1978]

Its a a little like conventional brazing, where as the filler material melts at a lower temp than the parent, so its not a weld, but a Eutectic bond. Its quite a bit lower on heat input than conventional mig, so it should help with you keeping the distortion to a minimum. You can either Pulse weld it or do it in short arc, use 100% Ar or Ar and small amount of Co2. Other than that, you just point and shoot like normal mig.

The Cu Al 8 (Ally Bronze) filler wire is used a lot in overlaying and cladding of wear plates and its very easily machinable afterwards.

 

[snowcat]

Snowcat, I personally wouldn't go near them, the idea of an on going re-occurring job is great, but if something should ever go wrong you don't want VOSA, HSE and legal briefs knocking on your door (and we are talking well loaded 8 wheel tipper brakes here).

I would look around for supplier of pattern parts there must be a firm producing them somewhere, I would start by contacting:


Industrial Friction Services Ltd.
Unit 1
Manor Road
West Thurrock
Grays
Essex
RM20 4BA

Tel: 01708-864935

One of the best commercial vehicle factors in the area, ask them to find and supply, then become a middle man "buy 'n' supply" is the way to go here, imho.

zzr

No patten available apparently, Scania are fierce about keeping patterns off the market. I take your point, however I don't think were going to be altering the structure of the part enough to cause a problem, The Transport managers pretty hot on that sort of thing, and wouldn't fit em unless he was 100%.....Most likely If it came off they could be done, It would be worth getting a procedure drawn up.. It could be quite easily paid for even if it was a £1000 or more..

 

[rusty69bus]

how about an automatic presurised gease pump like a scottoiler on a motor bike

 

[snowcat]

Its a a little like conventional brazing, where as the filler material melts at a lower temp than the parent, so its not a weld, but a Eutectic bond. Its quite a bit lower on heat input than conventional mig, so it should help with you keeping the distortion to a minimum. You can either Pulse weld it or do it in short arc, use 100% Ar or Ar and small amount of Co2. Other than that, you just point and shoot like normal mig.

The Cu Al 8 (Ally Bronze) filler wire is used a lot in overlaying and cladding of wear plates and its very easily machinable afterwards.

scuse me ignorance on this subject, but what are the advantages over an O/A braze??

how about an automatic presurised gease pump like a scottoiler on a motor bike

autolube, would be OK but again, it ain't gonna happen tho, this is the world of construction theres no TLC just patch it up and get it running.. Not even the 360s run auto lubes as a rule, and unless they have a care-full driver 5 years down the line all the pins are F***d, line boring here we go

 

[Welderpaul]

Fk the S Cams where's my *** machinin bits?

 

[snowcat]

Fk the S Cams where's my *** machinin bits?

Guess when your **** material turned up Paul, Tday at ,half 4..... Saws been busy apparently (hacksaw maybe) 5 phone calls of abuse and its here .... thats got to be a record on crap service, So pins be made tommorow.......

 

[Welderpaul]

Guess when your **** material turned up Paul, Tday at ,half 4..... Saws been busy apparently (hacksaw maybe) 5 phone calls of abuse and its here .... thats got to be a record on crap service, So pins be made tommorow.......

Only pullin yer pisser mate!
Saw been busy? Suppose thats a new one! One up on 'it's at the galvanisers'

 

[peterd51]

Hi,

could you turn the shaft down on a lathe so it's the same diameter all the way along and put a sleeve on it? Maybe brass, heated to get over the shaft and cooled to shrink it on?

Or would that reduce the strength too much?

If so, how about just sleeving the worst worn bit near the splines?

Regards
Peter

 

[matt1978]

scuse me ignorance on this subject, but what are the advantages over an O/A braze??

Its easier to do (no harder than normal mig welding), don't need to pre-heat the component, its much faster, more gap tolerant.

 

[Hitch]

Have they tried TTC

Theire catalogue has almost everything

 

[snowcat]

Only pullin yer pisser mate!
Saw been busy? Suppose thats a new one! One up on 'it's at the galvanisers'

Arseholes all because its a cut piece, how hard is it to cut a 5 1/4" bar, amazingly my saw managed to cut it six times ready for faceing in less than 10 days

Hi,

could you turn the shaft down on a lathe so it's the same diameter all the way along and put a sleeve on it? Maybe brass, heated to get over the shaft and cooled to shrink it on?


Or would that reduce the strength too much?

If so, how about just sleeving the worst worn bit near the splines?

Regards
Peter

There ****** hard I mean ****** hard, even a tip tool stands little chance against that sucker... as it stands its non machinable

Have they tried TTC

Theire catalogue has almost everything

I dunno they say there not avalible not a good idea to start sugesting where they might "get things" all of a sudden work might become kinda dry

 

[MrFluffy]

You could get that ground undersize, however that might mess with the induction hardening on the surface because the depth isnt very deep, its only a surface treatment. Could get them rehardened afterwards but where do you stop and say "is it worth doing".
However what I would look at is changing the bearing that runs on it slightly, any chance to line it with something like oillite or a thinwall ptfe bush? phosphor bronze breaks down and destroys the bearing surface a lot earlier than the alternatives...
Im guessing thats the cam the end of the slack adjuster pushes on. I used to be oily rag on a fleet of about 14 class 1's and the things we were religious about were greasing the nipples, and changing the diesel filters. Everything else got done at gv9 time