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Interesting topic!
My experience on my 1933 16/80 is that the original Lagonda machining was first class – must have been a tough place to be an apprentice. Holes are where they should be and individual parts are made to high standards of accuracy and practice. I don’t know about the new company’s standards…
The oddly-spaced holes may have been to direct more of the braking effort to the front, but I’m not familiar with the LG45 brake layout so that’s just a guess.I’m a mechanical engineer, not a metallurgist, but my two cents’ worth is:
With old castings and forgings, it’s hard to be sure what the composition of the metal really is. This does mean that your weld repair should be done by someone who really knows their stuff. Cast steel should be every bit as good as its wrought counterpart for tensile strength and ductility (except that it won’t have its yield strength raised by cold working). The same steel, but forged, will have somewhat better strength in the direction of metal flow, but forging was probably chosen more for cost reasons than for better properties.
As I said in an earlier posting, if I have to repair a worn hole, I will do it with brazing in a thin steel sleeve. The temperature for brazing is well below anything that will cause trouble for the lever metal, whatever it is, and the braze strength approaches that of steel. To me it’s the least risky option.
Having said that, there are many ways to solve the same problem!
AlecThis may help – It’s at least in the UK!
http://www.3trpd.co.uk/dmls.htmFor metals, that would be laser sintering. Very expensive! If I had to replicate parts like these, I think I would build them up from individual simple machined shapes welded together, then hand-finished to resemble castings. Once painted, they would look OK.
Hi David;
I’m toying with the idea of brazing in thin steel sleeves on mine. The net result should be close to original strength.
AlecI measured up my front brake levers as they were usually set up and assuming a gargantuan 300lb pedal force acting only on the front brakes, worked out the tensile stresses in the brake rods. The short rod connecting the brake pedal lever to the cross-shaft carries the highest load, some 56kpsi in this scenario, while the others carry less than half this. So you do need a good grade of steel for that one short rod, but the other rods could be a standard cold rolled low carbon steel. Sketch attached, I hope.
AlecHI David;
I did check out a brake rod today – it was 90,000 psi (600N/mm2) tensile strength on the outer surface and somewhat higher internally, about 100.000psi (660N/mm2). This is stronger than a low carbon cold drawn rod. Something with 0.5% carbon, cold drawn, maybe? I don’t know the European nomenclature but a 44SMn28 looked interesting and similar to 1144.
AlecHi David;
I’m working on that same area on my 16/80. I’ll probably use 1144 stressproof rod – here is a North American link. http://www.mcmaster.com/#grade-1144-steel-rods/=x0ubtt
I’ve been checking various bits with a hardness tester at work – I’ll take a brake rod in tomorrow and see what hardness it is – this gives me the steel’s tensile strength and it should confirm the above suggestion.Alec
Hi Colin – looks great! Any chance you can get some thickness measurements off the springs? Mine are not original except for three of the four leaves with the eyes in the ends and I’m unable to find the correct thickness for the other leaves. I’m guessing 0.218″…
Alec
Finished up redoing my gear lever – very happy with the results. I made the new reverse lever & pawl, rod, rod ends and screws out of stainless (the old ones were too pitted to easily salvage).
AlecDug out my old heat transfer book from school and ran some numbers with water and with ethylene glycol. For the situation I chose (steel 25mm pipe, 3 m long, flow 20mm/s, pipe at 80 degrees, inlet water at 60 degrees), the ethylene glycol only picked up 60% of the heat that the water did. The output temperature was lower too. Since our prewar engines were designed for water only (going by my 1933 manual), cooling with even standard antifreeze mix might start to be marginal in extreme conditions.
AlecInteresting chain. I found this link that seems to provide more information on the waterless coolant. I would be concerned with the lower heat transfer rate.
Alec
http://www.ffcars.com/forums/17-factory-five-roadsters/302124-you-using-evans-waterless-coolant.htmlColin;
I’ve had two experiences with Bars-Leak. In both cases, I didn’t know the cars had this stuff in their coolants. The first car had a massive water loss halfway through a 700 mile trip, the second (in a used car I had bought the day before) did the same, though fortunately close to home. This stuff does work, but it hides the leaks and as we all know, mechanical systems are generally not self-repairing. Sooner or later the leakage gap grows to the point where the Bars-Leak can’t fill it and the coolant just pours out. The only excuse for this stuff is as a “get-you-home” stopgap. Otherwise I would consign it to the far side of hell…
AlecHi Barry;
Yes, I removed everything that was bolted on. Only the big crossmembers and engine mounts are rivetted. Quite a job undoing all the bolts since this car was driven in Quebec and New Brunswick for about 17 years, year round. There is some rust visible at the rivetted joints, but the rivets are sound and it’s not going to be driven on salted roads anymore so I decided to leave it be. The worst (and only significant pitting} was between the wood body sills and frame, and where the copper grease lines were clipped to the frame. Otherwise it survived very well, due to so few enclosed spaces.
AlecThought I’d post a “before” and “after”. Cleaned up nicely!
Thanks for all the feedback. Maybe I’ll flip a coin… I’m leaning towards powder coating, just because the frame is completely stripped down (perfect opportunity) and I hear it’s a bit more durable.