Lotus Elan

Trunnions. Angles and greasing

PostPost by: 661 » Sat May 20, 2017 11:31 am

26GTS build for FIA racing.
I have to say I feel uncomfortable loading the trunnion abnormally by pushing the ball joint rearwards any further in order to gain castor. I found that with the ball joint centred on the top chassis supports it took 2 and a half washers each side to 'nip' the spherical bearings, whilst using 2 std AN washers each side of the ball joint. The ball joint appears to need probably at least 1 std and one thin washer each side to avoid the rubber fouling the TTR wishbones on suspension travel.
I've, therefore put 3 washers on the back support and 2 on the front. The trunnion seems to be OK with this but moving the ball joint back further ( by following TTR suggestion of moving more ball joint washers to the front)seems to make the suspension travel quite rough and the trunnion's poly bearings are trying to distort as the trunnion is angled. That really doesn't look like good engineering principle. So, I'll settle for the chassis ' determined castor plus the 2mm from the 1 extra rear washer.

And for greasing.........
With the solid vertical links, has anyone put a stubby grease nipple in the centre of the bottom surface of the trunnion?

Does anyone use M8 bolts for the ball joint to wishbone connection instead of 5/16 as the ball joint holes appear M8?
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PostPost by: vstibbard » Sat Jun 03, 2017 12:24 pm

Hi Graeme,

I ended up running less caster than TTR suggested due to the loading of the trunnion/wishbones. Note the trunnion is designed to run with heavy gearbox/diff (NON LSD) oil NOT grease. My replacement shell is about to leave UK, with the rebuild we'll bring slight offset into bottom wishbones trunnion bolt holes to allow the trunnion to sit at the TTR recommended caster angle and then yet to be worked through either offset bore the lower wishbone nylon bushes, fit a spherical inside the inner wishbone bush with dummy bush like covers!!.

I understand the cars are less nervous with more caster.

V
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PostPost by: 661 » Sat Jun 03, 2017 9:33 pm

vstibbard wrote:Hi Graeme,

I ended up running less caster than TTR suggested due to the loading of the trunnion/wishbones. Note the trunnion is designed to run with heavy gearbox/diff (NON LSD) oil NOT grease. My replacement shell is about to leave UK, with the rebuild we'll bring slight offset into bottom wishbones trunnion bolt holes to allow the trunnion to sit at the TTR recommended caster angle and then yet to be worked through either offset bore the lower wishbone nylon bushes, fit a spherical inside the inner wishbone bush with dummy bush like covers!!.

I understand the cars are less nervous with more caster.

V

I saw your shell at TTR.
I must speak to you in more detail about the castor stuff. I'll P M you when I've thought it through a bit more
Last edited by 661 on Mon Jun 05, 2017 6:16 pm, edited 1 time in total.
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PostPost by: patrics » Sun Jun 04, 2017 8:22 pm

Hi,
I was very unhappy about loading the trunnion so on mine I fitted spherical joints to the bottom arms.
No idea if that's okay with FIA

Regards
Steve
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PostPost by: elandoc » Sun Jun 18, 2017 9:52 am

vstibbard wrote:Hi Graeme,

I ended up running less caster than TTR suggested due to the loading of the trunnion/wishbones. Note the trunnion is designed to run with heavy gearbox/diff (NON LSD) oil NOT grease. My replacement shell is about to leave UK, with the rebuild we'll bring slight offset into bottom wishbones trunnion bolt holes to allow the trunnion to sit at the TTR recommended caster angle and then yet to be worked through either offset bore the lower wishbone nylon bushes, fit a spherical inside the inner wishbone bush with dummy bush like covers!!.

I understand the cars are less nervous with more caster.

V


It hasn't left yet? A mate up here had to replace the front chassis member and built in extra castor with angled uprights and matching angle in the bottom wishbone mount. I understand the Series 1 had a lot more castor than later models - not sure what TTR has engineered into his. I use the top and bottom spacer technique in my rally car, but of course am limited by binding.
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PostPost by: 661 » Mon Jun 19, 2017 8:00 pm

The first chassis were about 7 deg I understand and later, including the TTR replacements, about 3 deg.
I want to add degrees without straining/binding the trunnion/vertical link shaft. I may have a solution but it requires some bespoke bushes for the trunnion.
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PostPost by: vstibbard » Tue Jun 20, 2017 11:16 am

Hi Graeme,

It better be on the way by now! Apologies Iv'e not replied to your email, I've been sucked into a work vortex.

V
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PostPost by: vstibbard » Tue Jun 20, 2017 11:16 am

Hi Graeme,

It better be on the way by now! Apologies Iv'e not replied to your email, I've been sucked into a work vortex.

V
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