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KING PIN THRUST WASHERS - Dennis Nicholas - 28-11-2017
A technical question for the engineers.
The A7 has a flanged bush in the bottom of the stub axle to take the king pin (phosphor bronze?). Between that and the axle beam eye there is a thrust washer. The Big 7 is similar except no flange on the lower bush so the thrust washer runs directly on the stub axle and beam axle eyes. The big 7 beam has a recessed area around the bottom of the eye into which the thrust washer partly sits. Big 7 king pin is 5/8 inch dia.
I would obviously like the least possible wear to the stub and beam axle faces. Washers can easily be replaced
The big question is what should the thrust washer be made from????
There is information that they should be hardened steel.
The ones that came with my last set of KP and bushes were a tuffnol type material!
The A30/A35 Austin swivel pins (also the 5/8 inch dia. like the big 7 king pin) also have thrust washers and are same size apart from being 1 1/4 OD instead of smaller (I recon 1 1/8 for the big 7 beam and stub spot faces but easy enough to turn down the OD by mounting them on a bolt in a drill and filing the edges).
Bull Motif can supply the A30/35 thrusts but theirs are made in brass.
I am sure I read somewhere that hard and soft metal rubbing together then perversely the HARD metal will wear away quicker?
So - hardened steel, brass, phosphor bronze, Nylatron, tuffnol, ?, ?. What and why?
The last time I did the king pins I put a thin washer in the big 7 beam recess with araldite so the thrust was wearing against the washer and not the beam (washer could be replaced eventually). I will also araldite a thin washer onto the stub axle lower eye.
Dennis
RE: KING PIN THRUST WASHERS - Mike Costigan - 28-11-2017
(28-11-2017, 01:55 PM)Dennis Nicholas Wrote: ... I am sure I read somewhere that hard and soft metal rubbing together then perversely the HARD metal will wear away quicker?
This is correct; what happens is the soft material traps the abrasive material in its surface, and this then acts like sandpaper or a file to wear down the harder surface.
RE: KING PIN THRUST WASHERS - Dennis Nicholas - 29-11-2017
Here is a duplicate of my post on the associated thread about refacing. Perhaps I should have only had one subject, but I could see 2 issues.....cutters for refacing and thrust washer supply.
Alan....why would you not chose oilite? what technical reason? Here is blurb from Bowman .co.uk:- (just for interest the manufacturing process of sintering is the means where the metal has the pores into which the lubricant soaks)
Materials
Oilite bearings are manufactured in three standard materials.
1. Standard Oilite oil retaining tin bronze is the generally specified material. It gives good balance between strength, wear resistance, conformability and durability in operation. Ideal in a wide variety of applications where self-lubricating properties are required over a long period of time.
2. Super Oilite® is an iron copper material suited to high static loads and slow oscillatory motion.
3. Iron Oilite® are 100% iron oil-retaining bearings which provide an ideal solution in high stress low revolution applications.
Please see the Oilite® materials page for further technical details.
Dennis
RE: KING PIN THRUST WASHERS - Alan - 29-11-2017
Because what they avoided saying is that because it's a sintered material (i.e. Metal powder fused together) it's impact resistance isn't all that great, and I'm not convinced it will work in this application. Like has already been said, I don't know why you'd use this when correct parts are available. I'm not that familiar with big seven stuff, but I imagine there should be a bronze washer in the recess, with a hard steel washer above. An I bternet search should easily find both of these.
RE: KING PIN THRUST WASHERS - Chris KC - 29-11-2017
(29-11-2017, 11:49 AM)Alan Wrote: Because what they avoided saying is that because it's a sintered material (i.e. Metal powder fused together) it's impact resistance isn't all that great, and I'm not convinced it will work in this application. Like has already been said, I don't know why you'd use this when correct parts are available. I'm not that familiar with big seven stuff, but I imagine there should be a bronze washer in the recess, with a hard steel washer above. An I bternet search should easily find both of these.
Agree with Alan on this. Correct parts are not only available but work well. I think you are looking for a fix where there is no problem...
RE: KING PIN THRUST WASHERS - Jeff Taylor - 29-11-2017
(28-11-2017, 01:55 PM)Dennis Nicholas Wrote: A technical question for the engineers.
The A7 has a flanged bush in the bottom of the stub axle to take the king pin (phosphor bronze?). Between that and the axle beam eye there is a thrust washer. The Big 7 is similar except no flange on the lower bush so the thrust washer runs directly on the stub axle and beam axle eyes. The big 7 beam has a recessed area around the bottom of the eye into which the thrust washer partly sits. Big 7 king pin is 5/8 inch dia.
I would obviously like the least possible wear to the stub and beam axle faces. Washers can easily be replaced
The big question is what should the thrust washer be made from????
The first image below shows the bronze thrust washer originally fitted to MG TA / TB / TC - these are available from NTG but of course are the wrong size being I/D 3/4". The Morris Eight however uses 5/8" king pins just like the Big 7 and therefore uses bronze thrust washers of the correct I/D. Unfortunately as far as I'm aware (I also own a 1936 Morris 8 Tourer) the thrust washers are not available separately, only as part of a new king pin set which retails at around £90. The second image shows a Morris 8 king pin set.
RE: KING PIN THRUST WASHERS - Dennis Nicholas - 30-11-2017
Jeff
Thanks for the info. What is the source for the Morris 8 thrusts/king pins? ---Phone number, email? What is the Morris 8 thrust OD? Measuring on the second Morris 8 photo it seems to be the size I need of 1 1/16 inch. (note edited from 1 1/8")
For the thrust the ID of 5/8" is good, the OD needs to be 1 1/16 inch give or take a very small amount. (note edited from 1 1/8")
The Austin Big 7 club secretary has no thrusts and is considering getting a batch made in brass (have intimated that may be the wrong material). It could be to the mutual benefit of all to get together for batch purchases of items separately.
Dennis
RE: KING PIN THRUST WASHERS - Dennis Nicholas - 30-11-2017
I have just had another look at the BIG 7 front axle and measuring the recess in the underside of the ends realise that the OD of the thrust needs to be 1 1/16 inch to fit partly inside. (not 1 1/8".....I got that from measuring the largest face on the stub axle.
For those that have said the thrusts are easily available from our suppliers -- NO. Seven workshops says no, Mark Greening says no, A7c says NO. You are all thinking of the standard A7 not the BIG 7.
Standard 7 thrust ID 1/2" X OD 15/16" X thick 3/32" (0.15748")
Big 7 ID 5/8" X OD 1 1/16 X thickness ? Around 0.157" (4mm)?
Dennis
Will try to put some photos up.
RE: KING PIN THRUST WASHERS - Dennis Nicholas - 30-11-2017
Big 7 axle end. 5/8" king pin.
underside of kingpin eye showing recess that thrust washer partially fits into. Dia 1 1/6". Recess depth = 0.176 inches.
Big 7 Stub axle bottom thrust face showing about 1 1/4" of thrust face. Note there is no flange on the bottom king pin bush.
Big 7 stub axle underside of top king pin hole. note also about 1 1/4" dia. surface around king pin bush.
Hope this helps with visualisation of difference between 7 and big 7. (it takes the same hubs and 7" brakes)
Dennis
RE: KING PIN THRUST WASHERS - Stuart Giles - 30-11-2017
I have done the kingpins on a few Big Seven axles in the past, and was always lucky enough to pick up period -Thompson, Brivec etc. manufacture kingpin sets to do the work. These did include a bronze thrust washer as well as the hardened steel washer in the package. However, the Bronze thrust washer was never anywhere near thick enough; I assumed that this was due to the recess below the axle eye having worn deeper over the years.
Rather than put a stack of washers in there, I just turned up a pair of thicker thrust washers on the lathe. I used Colphos (a type of Phoshor Bronze) for these, because that's what I had in the workshop at the time. AFAIK they're still working OK, I think almost any bearing material would work there; but I wouldn't be happy to use Oilite (Sintered Bronze) as it is really brittle.