26 replies to this topic

[Spider]

Here's one test (not Minitastic though)

 

 

At standard ride height, 46 mm of rubber cone compression is needed to be able to go from rebound stop to 1/3 compression of the bump stop. The best Spring I found (which was actually a Minitastic one) only had 33 mm.

 

If you choose do use them, I'd suggest be careful with ride height settings.

 

<Edit: None of the springs I've tested were progressive in rate >

Edited by Moke Spider, 27 September 2015 - 10:01 PM.

[Ethel]

Surely altering the pitch (spacing) of the coils alters the rate? If you think of the force in vectors, altering the angle of the winding alters how much is in the vector acting along the axis of the rod and how much is perpendicular and doing the twisting that makes torsion springs springy. It should also mean the coils bind progressively, starting with the closest spaced.

[nicklouse]

Surely altering the pitch (spacing) of the coils alters the rate? If you think of the force in vectors, altering the angle of the winding alters how much is in the vector acting along the axis of the rod and how much is perpendicular and doing the twisting that makes torsion springs springy. It should also mean the coils bind progressively, starting with the closest spaced.

Nope it has no effect. It can be straight or bent but it is still the cross section that makes the spring rate. The distance just means that you might get more travel before coil bind. Which is why progresive springs often have varing coil diameters (not the wire) so that they can sit inside each other when compressed.

[nicklouse]

Here's one test (not Minitastic though)
 

 
At standard ride height, 46 mm of rubber cone compression is needed to be able to go from rebound stop to 1/3 compression of the bump stop. The best Spring I found (which was actually a Minitastic one) only had 33 mm.
 
If you choose do use them, I'd suggest be careful with ride height settings.
 
<Edit: None of the springs I've tested were progressive in rate >

I forgot to ask. Was this just the rubber donut or with a standard trumpet?

[Ethel]

I get the coil spring as wound up torsion bar analogy. There's more than the cross section to it though, a less tightly wound coil would straighten out into a longer torsion bar. The loading on a torsion bar is also perpendicular, that's impossible on a coil spring as the pitch would have to be, and stay, zero.

[Spider]

Ethal, regarding the coil springs and how they are wound, yes, your thinking is sound and right, however, in the case of springs for these cars, there's no room for little more than one and a half turns, some have about two, so there's just not enough turns in there to get some with higher pitching.
 
Going to a smaller wire size would help in this regards, however then the overall rate will be way too soft.
 
I spent around 3 months, every day, working with a Spring Engineer in their R & D Dept (Better Springs), with all the bells, whistles, tables (as it was then) and tricks in the book to get a conventional spring to work and take the place of the Donut, at the end of the period, the Engineer asked me one morning "Ever thought of using rubber?" (Mind you, we had many cones laying about - it was just that given the overall picture, he could clearly see and drew the same conclusion as Dr. Moulton did in the day).
 

 I forgot to ask. Was this just the rubber donut or with a standard trumpet?
 

 
I'll double check later, but I'm pretty sure that figures are using the stock front trumpet.

Edited by Moke Spider, 28 September 2015 - 04:57 AM.

[Ethel]

Don't get me wrong, I'm also of the opinion  rubber has many advantages. The only real downsides I know of are that age and temperature affect it much more. That'll be why Bl replaced it with hydrogas (that leaked fluid so aged as badly  ).

 

I agree it's a nigh on impossible task to make a steel spring work in a location specifically designed for a rubber one. Coil-overs make more sense. I wonder if anyone's looked at putting the bottom top arms on torsion bars running along the top of the subframe*? Many "Super-minis" took a similar approach for the rear end.

 

* could you even get anti roll by anchoring them to some sort of Z link????

Edited by Ethel, 28 September 2015 - 09:43 AM.
fuddled thinking

[Spider]

 I wonder if anyone's looked at putting the bottom arms on torsion bars running along the top of the subframe*?

 

I have one (of many ) designs for torsion bar for the rear end, still chewing that one over.

[carbon]

Ethal, regarding the coil springs and how they are wound, yes, your thinking is sound and right, however, in the case of springs for these cars, there's no room for little more than one and a half turns, some have about two, so there's just not enough turns in there to get some with higher pitching.
 
Going to a smaller wire size would help in this regards, however then the overall rate will be way too soft.
 
I spent around 3 months, every day, working with a Spring Engineer in their R & D Dept (Better Springs), with all the bells, whistles, tables (as it was then) and tricks in the book to get a conventional spring to work and take the place of the Donut, at the end of the period, the Engineer asked me one morning "Ever thought of using rubber?" (Mind you, we had many cones laying about - it was just that given the overall picture, he could clearly see and drew the same conclusion as Dr. Moulton did in the day).
 

 I forgot to ask. Was this just the rubber donut or with a standard trumpet?
 

 
I'll double check later, but I'm pretty sure that figures are using the stock front trumpet.

 

Would be interesting to see effect of different trumpet types on the rubber spring rate, suspect this will make quite a difference.

 

And there are quite a few combinations with different trumpets and alternative rubber spring...

Edited by carbon, 28 September 2015 - 05:03 PM.

[Cooperman]

Let's go back to the reason coil springs were ever used on the Mini. In circuit racing where the tracks are very smooth there is a need for a high spring poundage to reduce initial body roll as the ordinary rubber spring 'loads-up'. So a high-rate coil spring will work. However, this would be a single rate spring as the total deflection is small and coil binding is not an issue. The cars are usually lightened and there are no high bump loads.

On a normal road, however, there are bumps and a super high rate spring would not keep the wheels in contact with the road. So a rising rate spring is needed with the initial rate being relatively low and rising as it deflects to prevent coil-binding or the suspension hitting the bump stops, both conditions which would cause a distinct lack of steering control.

So what type of spring can best give this carefully calculated rising rate? How about a rubber cone which will always be low rate initially and the rate of increasing load per mm of deflection is easy to calculate and then manufacture.

One might guess that that was how Mr. Moulton designed the original, and still the best, Mini springs. They are, quite simply, superb.

I've never been able to see any benefit whatsoever from using coil springs on a road or a rally Mini.

[Spider]

Would be interesting to see effect of different trumpet types on the rubber spring rate, suspect this will make quite a difference.

 

And there are quite a few combinations with different trumpets and alternative rubber spring...

 

 

I've done a number of tests, on and off car, with different designs, bigger flanges, smaller, funny shaped and inverted ones too.

 

One thing I learnt from those tests very early in the piece is the Rubber Cone itself actually gives a fairly Linear Spring rate, the Progressive Rate comes from the shape and size of the flange on the Trumpet.

 

The other thing to draw from this is that there are Hilos and there are Hilos. As they are a non-standard part and there is no standard design for them, different manufacturer's and types of them will give different characteristics, usually the cheaper ones give a softer but sharper and earlier change in rate as they have less material in them. I'm not saying here that any of them are no good, that's not the case, just that they will be different between each other.

Edited by Moke Spider, 09 November 2015 - 07:16 PM.

[carbon]

Thanks Moke Spider, you are again on the money. The early Hi-Los I have seen from Ripspeed have a very wide flange with unusual profile, which I would expect to give a higher progressive rate.

 

I have a pair of these early Hi-Los fitted on car using the original pre-76 'hard' rubber springs, and it is a very firm ride indeed.