Lotus Elan

Another post about uprights / trunnions

PostPost by: Chancer » Thu Dec 07, 2017 7:58 pm

MarkDa wrote:Has anyone gone trunnionless with them?
Not much use to Jon as he's bought new already, but it would be interesting to hear.


On a Caterham yes, the rose joints soon wear as they are exposed and unprotected, with the extra weight of an Elan the wear would be more consequent.

I have a bike engined Caterham where I modified the trunnion uprights for a rose jointed lower wishbone, I turned the thread off on my lathe and screwcut a thread on the exposed portion for a nyloc nut, trouble is there is the lubrication bore up the middle and there aint much meat left, even Steve Broad would not take lightness to that extreme,

I must like living dangerously and they have held out to date, no way would I trust myself to someone elses machining with so little meat remaining.

I would say that a solid trunnionless upright (no lube hole) would be a lot stronger than the OE threaded version.
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PostPost by: JonB » Thu Dec 07, 2017 8:14 pm

Sorry, what's a trunnionless upright if it isn't the rose jointed type? Canley list them but there's no picture.
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PostPost by: MarkDa » Thu Dec 07, 2017 8:26 pm

By too late for Jon I meant that trunnions and bushes already bought.

Photo and description of CC upright here

https://www.canleyclassics.com/suspensi ... ension-kit

They look pretty substantial and are pretty pricey, but when you factor in reunions and bushes the premium may not be too enormous for going maintenance free.
And there's the extra resistance to potholes etc.
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PostPost by: Chancer » Fri Dec 08, 2017 12:19 am

JonB wrote:Sorry, what's a trunnionless upright if it isn't the rose jointed type? Canley list them but there's no picture.


Yes, the rose jointed type, a plain shaft at the bottom not a threaded one with a hole up the centre, not to keen on the whole thin being retained by a circlip like on the Caterham suspension though, maybe for an Elan/Triumph its a better set up.
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PostPost by: JonB » Fri Dec 08, 2017 10:09 am

I have decided to get a set of Canly uprights. Standard trunnion type....

Pop goes the weasel.
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PostPost by: vincereynard » Fri Dec 08, 2017 10:43 am

Does anyone know the logic behind Triumph fitting the dreaded trunnions in the first place?

They fitted a nice ball joint to the top, why not the same at the bottom? Same goes for the after market systems with an exposed rose joint. Why not a simple, lubricated, sealed ball joint?

I've also had a couple of failures over the years, both near side, always at full lock, also at slow speed luckily.

One on a Vitesse convertible. I had been doing an easy 80mph on the A38 into Plymouth a minute or so earlier, down the front, sharp left around a traffic island and nasty crunches as the whole plot hit the road.
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PostPost by: JonB » Fri Dec 08, 2017 11:21 am

I think you would find much conjecture on that question if you had a look round some Triumph forums!

My own take on the subject is as follows.

If we consider the difference between a ball joint and a trunnion in terms of how they move, we can see that the trunnion is superior in that it limits the degrees of freedom of the joint to only that which is strictly required by the suspension.

I can see a lower ball joint would allow for more twisting of the upright under braking (camber change effectively) and you would need a stronger lower wishbone as a result. If you look at modern lower arms with ball joints they are quite substantial box section units, whereas ours uses a weaker open section design, and it is in two pieces. This gives more opportunity for flex under braking, and the trunnion design acts to reduce this tendency.

Whether or not that was the intention, I couldn't say. It's simple, it works, and is safe if properly maintained. I now deem mine unsafe, but they didn't let go on me, fortunately.
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PostPost by: MarkDa » Fri Dec 08, 2017 1:08 pm

You probably need to go back to their 50s cars as well for a design that they just carried forward.
Trunnions were what a lot of cars as well as triumphs had then.
One of the advantages is the significant bearing area of all the thread which combined with the rigidity in the other two planes provided a durable solution.
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PostPost by: vincereynard » Fri Dec 08, 2017 1:27 pm

MarkDa wrote:You probably need to go back to their 50s cars as well for a design that they just carried forward.
Reunions were what a lot of cars as well as triumphs had then.
One of the advantages is the significant bearing area of all the thread which combined with the rigidity in the other two planes provided a durable solution.


Were those reunions in the 50's or of earlier cars? :o

I know Morris Minors had them and where also well known for collapsing!
Although I thought that was the top joint.

Minors and Heralds - A battle of the Titans!
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PostPost by: vincereynard » Fri Dec 08, 2017 3:29 pm

JonB wrote:I have decided to get a set of Canly uprights. Standard trunnion type....

Pop goes the weasel.



LOTUS = Open your wallet and repeat "help yourself".
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PostPost by: MarkDa » Fri Dec 08, 2017 3:57 pm

Long live predictive text!!
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PostPost by: JonB » Fri Dec 08, 2017 4:39 pm

That's quite funny, Vince, but it's the same with all old cars. As has been observed before though, it works out cheaper than a modern car.

Oh well, at least I will know it is done right. My only worry was about the quality of the steel and machining. But Canley have reassured me.
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PostPost by: MarkDa » Fri Dec 08, 2017 7:46 pm

Yes a range of 'BMC' cars had a substantial lower wishbone and a lever arm shock absorber as top link with a trunnion onto the upright.
Minor, Spridget etc.
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PostPost by: Chancer » Fri Dec 08, 2017 8:20 pm

The Herald predecessor the Standard 8 had top and bottom trunnions, quicker to replace than king pins and bushes together with the necessary in line reaming.
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PostPost by: MarkDa » Fri Dec 08, 2017 8:44 pm

Thinking about it the minor and midget were kingpin designs with plain trunnion at the top.
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