Swapping your king/link pins for heim joints

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mactaylor
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Re: Swapping your king/link pins for heim joints

Post by mactaylor » Sat Jul 15, 2017 9:30 pm

Hi All. I bought Greg Mackies car and it is a great car too drive! I have plenty of pictures of the car fully loaded up with very little flex in the front! I run the yokohama A050 gs tyres in 205/50/16 on the front and 215/50/16 in the rear. I am heading down the path of full slicks all round in 265/605/16. Cant wail to test it out! Hopefully the turbo conversion will happen soon too!

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petew
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Re: Swapping your king/link pins for heim joints

Post by petew » Sun Jul 16, 2017 1:28 am

Sooooo jealous. :twisted:

Bring on the turbo! :D

mactaylor
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Re: Swapping your king/link pins for heim joints

Post by mactaylor » Mon Jul 17, 2017 1:55 am

Working on brakes at the moment! I have 356 alloy drums at the moment and they are fine! However I did run out of pedal at a race track a while ago and with the added HP I dont want a repeat! Im trying to keep the wide five but the price and reliability of suppliers is a little worrying! May end up making my own! Im going to stay with the linkpin setup and swing axle but I will need to up the spring rate in the rear! Do not be jealous pete! Just join the club! Linkpin for the win!

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4agedub
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Re: Swapping your king/link pins for heim joints

Post by 4agedub » Mon Jul 17, 2017 2:08 am

MacTaylor, I still have some old pics of your car. Greg helped out quite a bit when we did setup on the swing axle car.

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I have now driven both swing axle and irs. The irs / McPherson car is so much easier to drive fast and is more predictable (even with minimal setup work since building it). The biggest difference is on corner turn in. The swing axle car is slow to respond on corner turn in, but good on mid and corner exit.
Superbug Racing Team
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mactaylor
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Re: Swapping your king/link pins for heim joints

Post by mactaylor » Mon Jul 17, 2017 3:33 am

Hi Louis! Suspension has changed a bit since then! Not heaps but a fair bit! In the rear it is coil over with a long triangular trailing arm. Front is basically the same but better front anti roll bar. Turn in is one of the best things about this car! You can be loose as on the brakes trailing to the apex, then plant the throttle and its a juggle on the way out! Biggest weird thing I get is a slide, grip, slide thing happening on fast corners! Have not worked out what is happening yet! Im thinking its not enough rear spring! As it loads up it goes negative camber, then as it is fully compressed it goes to positive camber as the body rolls! Well thats my thoughts. Please feel free to share your thoughts as we are the some of the only blokes in the world at this level! There are a few but it is a limited number.

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FJCamper
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Re: Swapping your king/link pins for heim joints

Post by FJCamper » Tue Jul 18, 2017 9:53 am

Slide-Grip-Slide!

Not saying I know the answer to your particular problem, but slide-grip-slide very accurately describes a common Brit car handling quirk.

The older Triumphs and MG's were bad about this because of overstiff suspensions. Some described it as bouncing sideways, some blamed in on tires that didn't have enough self-aligning torque and the slide-grip-slide was the last stage before slide-spin.

The tires we use today grip. They do not slide gracefully, and we swing axle guys like and use controlled slides.

I'd experiment with tire/tyre pressures first, to see if it makes any difference.

FJC

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Re: Swapping your king/link pins for heim joints

Post by Ol'fogasaurus » Tue Jul 18, 2017 10:21 am

FJ, todays rubber bands on large dia. and wide rims (donuts) don't have much sidewall to them. It used to be that you needed some sidewall action (and from the pic... 3-wheels on the ground :wink: ) with too stiff of sidewalls causing similar problems. Would that still be true today?

Just curious as this has piqued my interest.
Lee

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mactaylor
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Re: Swapping your king/link pins for heim joints

Post by mactaylor » Tue Jul 18, 2017 11:15 am

Hi FJC. I have played with the tyre pressures a fair bit and have found that 30 psi hot gives the best lap times. I get about 150klms out of a set of rear tyres. The slide grip slide problem only happens on fastish corners say above 100kph where i have run out of hp to powerslide the car. Anyway its all about to change again with the new slicks! Car will be wider by about 100mm so will need changes to account for this. Funny thing I found with the new slicks is they are lighter than the R spec tyres! Win win!

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FJCamper
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Re: Swapping your king/link pins for heim joints

Post by FJCamper » Tue Jul 18, 2017 1:43 pm

Hi McTaylor,

Ah. We have a clue. The rubber is trying to stick once you run out of throttle to force a slide.

It's tires.

https://www.youtube.com/watch?v=Vgd30thmPsc (Road Atlanta)

Here's a video of a recent short sprint race, from green to checkered flag, of our IRS Ghia, ball joint front axle, exceeding our tires. The Ghia gets less and less precise in the corners as the Falken street radials (185x15) get hot and "greasy."

We, as a class, all pass under the bridge to the checkered in one group, so the Ghia on its hot rod 1600cc debut wasn't disgraced. We'll be faster at Daytona.

The rattle you hear is from a loose tow ring near the camera.

FJC

mactaylor
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Re: Swapping your king/link pins for heim joints

Post by mactaylor » Tue Jul 18, 2017 6:35 pm

FJC I probably worded that wrong Im not trying to slide im just powering on as much as the corner and car will allow. On the slower corners im having to modulate the throttle more as wheel spin in the first two gears is readily available, I still think it might be in the setup rather than the tyres themselves. BTW car has a solid spool and its awesome!

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petew
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Re: Swapping your king/link pins for heim joints

Post by petew » Tue Jul 18, 2017 8:41 pm

mactaylor wrote:
Tue Jul 18, 2017 6:35 pm
FJC I probably worded that wrong Im not trying to slide im just powering on as much as the corner and car will allow. On the slower corners im having to modulate the throttle more as wheel spin in the first two gears is readily available, I still think it might be in the setup rather than the tyres themselves. BTW car has a solid spool and its awesome!
Could it be that what you're experiencing is slight power transfer between the inside and outside rear wheels? That would be down to the spool. Like me, the thought of a a quaife or similar make your wallet gasp. Might sticker tyres and a more aggressive attitude be a fix in getting the outside wheel to remain planted?

mactaylor
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Re: Swapping your king/link pins for heim joints

Post by mactaylor » Wed Jul 19, 2017 3:02 am

Hey Pete I do not know! I would have thought that the spool would more likely promote a more reliable and consistant exit under power! The normal thing that a full spool does is promote under steer on turn in then over steer on the way out! These are not a problem! My reasoning is as you hit the gas all the power is being distroed evenly,as long as your pointed roughly in the right direction all should be equal, so the only unaccounted for movement has to be suspension. Its just weird! and I hope it does not get worse the wider and more grip I have! I know if i firm it right up it will be a oversteering monster! And wreck the reasonably finely tuned chassis i have!

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