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Phase 1 torsion bars

 
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Dave-M
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Joined: 20 Jan 2006
Posts: 376
Location: Yorkshire, England

PostPosted: Sat Dec 05, 2020 5:23 pm    Post subject: Phase 1 torsion bars Reply with quote

After seeing the discussion on Farcebook regarding the "different" torsion bars used on the P1 I thought this calculator might be useful.

It should be useful for interested parties to compare the spring rates for their particular torsion bar diameter. All you need are the length of the bar between the mountings. the length of the bottom arm between the centres of the torsion bar and the upright along with the diameter of the torsion bar.

All dimensions are in inches and the calculated spring rate is pound/inches as is usual with coil springs.

I put this on the forum as it will be accessable in years to come, long after the Facebook page has dissapeared.

It would be good if the calculated results could be posted here for the benefit of future interested parties.

Please read all the other posts in this thread before using the calculator.

Here is the link :-
https://swayaway.com/tech-room/torsion-bar-wheel-rate-calculator/

Regards, Dave
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Ph.2 Ford 1500 GT
GT with Rochdale Chassis


Last edited by Dave-M on Fri Dec 11, 2020 5:18 pm; edited 2 times in total
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keith hamer
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Joined: 28 Jan 2006
Posts: 286
Location: Ellesmere Port

PostPosted: Fri Dec 11, 2020 9:15 am    Post subject: Torsion bar calc Reply with quote

From the details below from one of my spare Riley torsion bars the calculator shows the wheel rate as 84.7 lbs/in

Dimensions are :-
Torsion bar active length 34.25"
Bar diameter 0.76"
bottom arm length 11.25"
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Dave-M
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Joined: 20 Jan 2006
Posts: 376
Location: Yorkshire, England

PostPosted: Fri Dec 11, 2020 5:15 pm    Post subject: Torsion bar Reply with quote

Keith, Thanks for the input and the relevant numbers, my car is a P2 so I had nothing to measure for checking the accuracy.

However I must apologise for not being clear in my original post (now edited) and not noticing that on the calculator it talks about wheel rate and not spring rate as it should.

What it does is give a comparison of the spring rate at the outer end of the
bottom arm which should be the same for all Phase 1 cars so the spring rates can be compared accuratley for different bar diameters.

My understanding is that the P1 could be fitted with M.Minor or Riley front drums (different widths), some cars have had disc conversions and different width wheels. This will need a bit of measuring to give an accurate "Wheel Rate" figure.

We need to replace the Lower arm dimension with the following:-

The horizontal distance from the torsion bar centre line to the wheel mounting face of the hub and subrtact the ET number of the particular wheels used (if ET is positive) or add the ET number (if ET is negative)

All dimensions should be in inches so you will need to divide the ET by 25.4.

This should give us an accurate lever length to input into the calculator which will give you the wheel rate at the centre of the tyre contact patch for your particular car.

If my ramblings are a little difficult to follow I could add a sketch or two to clarify if needed.

Regards, Dave
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Ph.2 Ford 1500 GT
GT with Rochdale Chassis
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keith hamer
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Posts: 286
Location: Ellesmere Port

PostPosted: Sat Dec 12, 2020 9:19 am    Post subject: torsion bar Reply with quote

No need for clarification, we have been designing and building race cars for the best part of 40 years, we are familiar with the concept of wheel rate versus spring rate.
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Dave-M
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Location: Yorkshire, England

PostPosted: Mon Dec 14, 2020 10:32 am    Post subject: Torsion bar Reply with quote

Keith, Your Knowledge, Experience and Ability with all things "Rochdale" is without question.

The intention in my last past was that the first line be directed directly to you and the rest of the post was to be a continuation of the original post, however upon re-reading it, I can see how it could look as though I was being patronising toward you. This was certainly not my intention and I deeply regret this.

I really must be more careful with future posts. With so few people using the forum it's important we all stay friendly

Regards, Dave
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keith hamer
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Joined: 28 Jan 2006
Posts: 286
Location: Ellesmere Port

PostPosted: Tue Dec 15, 2020 9:13 am    Post subject: torsion bars Reply with quote

No problem Dave, your explanation is definitely appreciated, it can be difficult to get ones head around all these technical phrases, and particularly with the concept of spring rates where a bar is concerned rather than a spring.
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