Thinking through a trunnion conversion

[BiTurbo228]

I've been thinking recently about trying to make my own trunnion conversion. Partially because I just like making things and partially because I'm a tight b*stard

I've just picked up a set of 3 GT6 uprights from eBay for experimentation, so I thought I would test out some thoughts.

It's my understanding that the weak point on the trunnioned uprights is the threaded part itself, no? I'm assuming it snaps at the end of the threaded section.

So, the plan would be to make up a threaded sleeve with either a 1" or 3/4" OD to thread over the trunnion bolt, with an unthreaded section to butt up against the vertical link where it would then be welded in place. A rose joint would then go over this (butting up against a shoulder machined/welded onto the sleeve?).

The rose joint would then need to thread into/onto a block that would bolt into the wishbone.

The issues I can forsee so far are that there's very little clearance between where the block needs to go and the base of the shock, meaning you wouldn't be able to get a locknut on there.

This means that you would either need to move the spring/shock mount to above the wishbone (or the block below) meaning you'd need adjustable shocks to lower it back down again, or move it forward meaning you'd need adjustable wishbones up top to sort the camber.

Just being able to purchase a carrier from Canleys would probably sort the above, but they've got their own (fixable) design issues.

Thoughts?

Waste of time? (probably)

Interesting thought experiment? (definitely)

When will I actually get round to trying it? (judging by how I accumulate projects, likely when I retire - for info I'm 25....)

[Clive]

I woudn't want my uprights welded.....They are cast I think?

I am renowned for being careful with cash, and when it came to building my spitfire I bought teh CC conversion, it was very little extra over new std parts.

If you want to "play" then look at alternative uprights and arms? But the suspension is a very good design. Apart from trunnion issues when older and abused.

[BiTurbo228]

Quoted from cliftyhanger

I woudn't want my uprights welded.....They are cast I think?

I am renowned for being careful with cash, and when it came to building my spitfire I bought teh CC conversion, it was very little extra over new std parts.

If you want to "play" then look at alternative uprights and arms? But the suspension is a very good design. Apart from trunnion issues when older and abused.

Yeah I've got the CC conversion for my Spit 6, I was thinking of having an experiment with my next Spit project.

The uprights are cast, but from what I understand they're cast steel which can be welded quite readily (provided you pre-heat it slowly to prevent cracks between hot and cold bits).

It's the old and abused bit that I'm concerned about, given that I'm using old parts and plan on doing a bit of abusing myself....

[toolmaker]

why are you even thinking about trunnions aged 25?

[BiTurbo228]

Quoted from toolmaker

why are you even thinking about trunnions aged 25?

The GF rolls her eyes despairingly at it too

In reality, better to think about trunnions than don a flat cap and try and get my Veedub to scrape along the ground like the stereotypical 25-year-old car enthusiast

[toolmaker]

[BiTurbo228]

Oh no! I've mixed up my MGs and my VWs.

It's a flat-brimmed hat, not a flat cap

[sparky_spit]

What about trying to strengthen what you have rather than re-make it. Vegas Steve had an idea some years ago, and I'm not sure whether he actually did it or not, of drilling out the existing oilway, and inserting a high tensile rod up through the new drilling and into the body of the vertical link to provide greater strength to the top of the threaded area.  This drilling would either be bottom tapped to accept a high tensile countersunk bolt or the rod bonded in place. Or both. I think his intended size of the rod/bolt was 8mm.

Lubrication for the bronze trunnion would be provided by a new oil nipple at the top of the bronze part itself.

I thought about trying it myself, and messed about for a bit trying to set it up in the lathe but then something else came along and it went into the "maybe-one-day department".  I ended up buying some CC kits like everyone else.

It would be nice to see somebody make the idea work though....

[Gt6s]

Vertical links are DROP FORGED STEEL not cast ! Will weld no problem at all.

Laurence

[GT6 M]

they O snap right at the end, bit where its just left the taper.

generally rust pits eatin into thread
which aint rolled, but cut, an can be quite wuff wuff if looked at under a magnyfying glass

be better to ..polish  first thread away,and then the loaded area is deeper int carrier.


Just oot of curiosity,they seem to goawol after 30-45 yers,
Ive seen modern ball joints go awolafter 8 years on cars
Vauxhalls an fords wer a common sight in me marras garage ev,n lost the bottom ball joint

So really, a new,n is going to last a long long time,esp if its well lubed often

M

[sparky_spit]

Quoted from GT6 M

So really, a new,n is going to last a long long time,esp if its well lubed often

M

I'm debating whether to open this subject again as it got a bit heated last time.   Oh what the heck....

Sorry , link no longer available

[junkuser]

That is a good thread Sparky.
It brings up a lot of worthwhile things to think about and evaluate from which others can make their own decisions.
Good pictures showing what happened in one case at least.
Bill's point about the step in the drilling in this particular upright would certainly localise stress.
Marcus mentioning corrosion is the one I had thought about, especially with the design of the "seal" that runs here which seems designed to hold water in the area, particularly as it ages and loses its flexibility.

As for Rose joints, the critical thing in my mind is getting the directions of loading correct.
The lower end Rose would be subjected to vertical loadings and lateral loadings but Rose joints are primarily designed for one direction of loading.

Just my feelings.

[BiTurbo228]

Quoted from sparky_spit

I'm debating whether to open this subject again as it got a bit heated last time.   Oh what the heck....

Sorry , link no longer available

Good link, with a lot of good information, especially towards the end.

I definitely agree with the 'want quality, then pay for quality' attitude as that's what brings high quality parts to market so I may just go for the Canleys VL (with a modified carrier) simply to support its continued availability.

I'd still like to experiment though, just in case continued supply becomes a problem (and I've already got myself 3 sets of used VLs that I otherwise have no use for). Drilling, tapping and winding in a machine screw to strengthen the VL would be an option.

Another thought. What about cutting off a balljoint taper from another VL and welding it on in place of the trunnion. Then you could mount something like the pictured balljoint onto the wishbone with minimal welding.

I'd have to be damn sure of my welding though, and get it sonically tested....