DIY rear hubs

[ChrisShaw]

Hi all,

Had a bit of a mad thought and wanted to discuss. Since some kind folk here have made the cad files for the rear hubs publicly available I was considering how to use them. Has anyone considered 3D printing the hub, making a sand mould, and casting the hubs from the same grade aluminium that they were originally made from?

[Thartje]

There are some billet CNC hubs out there now. I think that would be the best route, or picking up a used set as they become available.

[ChrisShaw]

Yeah, they are the best current solution, I was just floating the idea of casting some replacements also since the originals were cast aluminium. I see people cast numerous car parts from aluminium so just wondered about these.

[superdavelotus]

Alan Voigts Gearboxes already make the hubs cast like the originals for the past couple of years.

 

[mike_sekinger]

I don`t think that Alan Voigts offer them any more as they had a number of failures in the field.

[superdavelotus]

1 hour ago, mike_sekinger said:

I don`t think that Alan Voigts offer them any more as they had a number of failures in the field.

I didn't realise this Mike, when did this happen?

[mike_sekinger]

@superdavelotus Not sure exactly, but this was one of the primary drivers for JAE putting up the funding for advance orders that helped to make the CNC upright project viable.  

[ChrisShaw]

That’s interesting. I spoke to one engineer who was talking about high-pressure casting, presumably to minimise the risk of voids?

I was also considering making an equivalent from chromoly, it would be heavier but at least would be more robust.

 

[andydclements]

I guess casting would need enlarged mould compared to the actual machined items, due to shrinkage as the metal solidifies and cools, but that should be easy enough to factor in, then final machining to the standard size anyway.

[EXCEL V8]

The choice of alloy, and just as important, the heat treatment have a major impact on the strength of the finished items.  I've had stuff cast in LM25 and no heat treatment and it stays fairly soft, but LM27 with heat treatment gives a really tough casting - you can tell when machining it that it is much harder.  I wonder if there is any info on Lotus' choice of alloy/heat treatment?  I've considered having the Elite rear hub carriers cast and machined to take a modern "cassette" type wheel bearing assembly like the later Esprit.  Done nothing about it though! 🙄

Pete

[ChrisShaw]

I read somewhere that the grade of aluminium used by lotus was A356.0 T6 (which Google told me was a fairly common casting alloy) but I can’t find an official source. I don’t know much about the alloy itself or how it compares to LM27?

[sailorbob]

The material specification for the rear hub carriers used on vehicles with ABS sensors was LM25TF to BS 1490 with a Brinell hardness of 90 - 110. I imagine the earlier hubs would have been the same.