Questions to and answers from Barry Whitehead about his rubber suspension.
1/ How did you design the Quadrants, are they a 1 to 1 relationship or is there some leverage?
I just made them to fit in the car, and then put enough layers of rubber to give me the wheel rate I wanted. Very suck it and see !!
2/ Do you take the weight off the wheels when the car is not in use?
Not normally, because when I do the rubbers set differently for a while and the adjusters have to be altered from time to time.
3/ Where did you buy the webbing and how long has it been on the car?
I contacted Pirelli and got it from them. Some of the rubbers have been in use for 5 or more years: Tho' they do stiffen up with time. It is worth checking the wheel rates from time to time
4/ Are the webbing mounts/yokes an item off the shelf or did you make them? I make everything myself, for better or for worse.
5/ Do you really need the Sh/Abs or is it just belt and braces? As I compete, it is always best to have the ability to alter the handling with the various adjustments, Sh.Abs., Anti-Roll bars., and tyre pressures.
6/ What type of motor is it in the Pic, looks like a big Japanese bike motor? Suzuki GSXR1100WP; I am now fitting a GSXR1000K8.
7/ How much does each corner weigh on your car (unsprung)? A sore point; too heavy. I can't remember exactly, but the bathroom scales give me an all up weight of about 860lb, with about 18-13 split: That does not give me unsprung, I cannot remember that. It is all written down somewhere, but at the moment I cannot find it.
Tuesday, September 23, 2008
Thursday, September 11, 2008
Pix Explained
Ref. from quadrant; it is just the way I made it; I could have done it differently, but I did not. The front rubbers are 5 1/2 in between the pivots at rest, and 6 3/4 in static at ride height. In a sense the longer their movement the less non-linear they are.
My previous car, similar in many ways, had taller rear uprights, so the Sh.Abs. could go from the upright down to the chassis. On this car I put the upright (I make my own) inside the rear wheel, and so I had to do the rather clumsy additional bell crank for the Sh.Abs. and also for the T bar for the Anti-Roll set up (See .jpg). The rear rubbers are 5in between pivots at rest, and 7 1/4 at ride height: Just under 50% stetch.
I am thinking of making my next car (No 7), and I intend to tidy up and lighten both the bits you have asked about. I am 77, and have been competing and building my own cars for 40 years !
The rubber bands are very definitely rising rate, which I discovered by taking a band and pulling it down between 2 bathroom scales - I will leave you to do that as I have long ago lost the graph I drew. The rubber is Pirelli Extra Flex, which they sell in rolls, but I do not know the spec. I merely used what Alan S was using.
In general I guess that the rubber is more self damping than steel springs so puts less need for Sh.Abs.ers. I have always used Anti-Roll bars (? sway bars to you) as I do not think the rubber has any influence there.
I use Pirelli Extraflex (I think !). I use 1, 1 1/2, and 2 in. wide. (I do not use 1in now).
As the years go by the rubber stiffens up quite a bit; tho' in initial setting up it stretched for a while in use.
I mount the bands in multiples of 2 with a double yoke which has a centre piece for the pull rods. See the pictures when they arrive.
I think Alan's diagram in his book is 'iffy' when he outs the bands round a pivot, even with needle race inside. I have always put my rubbers in straight pull.
I try to get round the rising rate characteristic when working out my wheel rate by sitting that end of the car on bathroom scales, pulling it down 1/2 in, then lifting it 1/2 in, and I assume (!!!) that the difference in the scales is more or less the lb/in figure, obviously divided by 2 for each wheel.
Originally I got multiple bands sewn in about 1/8 in increments: Now I put a single loop in one end and wrap it round the two pivots and lock it with clamping spikes.
If you take a single loop and pull it down against scales you will see the curve; my own guess work is not to stretch it more than 50% on the car.
My weakness is that I still use shock absorbers and the quadrants etc. add to the weight. Part of the reason for the Sh.Abs. is that if the bands broke (they never have in 24 years) then the Sh.Abs. stops me hitting the ground !
My previous car, similar in many ways, had taller rear uprights, so the Sh.Abs. could go from the upright down to the chassis. On this car I put the upright (I make my own) inside the rear wheel, and so I had to do the rather clumsy additional bell crank for the Sh.Abs. and also for the T bar for the Anti-Roll set up (See .jpg). The rear rubbers are 5in between pivots at rest, and 7 1/4 at ride height: Just under 50% stetch.
I am thinking of making my next car (No 7), and I intend to tidy up and lighten both the bits you have asked about. I am 77, and have been competing and building my own cars for 40 years !
The rubber bands are very definitely rising rate, which I discovered by taking a band and pulling it down between 2 bathroom scales - I will leave you to do that as I have long ago lost the graph I drew. The rubber is Pirelli Extra Flex, which they sell in rolls, but I do not know the spec. I merely used what Alan S was using.
In general I guess that the rubber is more self damping than steel springs so puts less need for Sh.Abs.ers. I have always used Anti-Roll bars (? sway bars to you) as I do not think the rubber has any influence there.
I use Pirelli Extraflex (I think !). I use 1, 1 1/2, and 2 in. wide. (I do not use 1in now).
As the years go by the rubber stiffens up quite a bit; tho' in initial setting up it stretched for a while in use.
I mount the bands in multiples of 2 with a double yoke which has a centre piece for the pull rods. See the pictures when they arrive.
I think Alan's diagram in his book is 'iffy' when he outs the bands round a pivot, even with needle race inside. I have always put my rubbers in straight pull.
I try to get round the rising rate characteristic when working out my wheel rate by sitting that end of the car on bathroom scales, pulling it down 1/2 in, then lifting it 1/2 in, and I assume (!!!) that the difference in the scales is more or less the lb/in figure, obviously divided by 2 for each wheel.
Originally I got multiple bands sewn in about 1/8 in increments: Now I put a single loop in one end and wrap it round the two pivots and lock it with clamping spikes.
If you take a single loop and pull it down against scales you will see the curve; my own guess work is not to stretch it more than 50% on the car.
My weakness is that I still use shock absorbers and the quadrants etc. add to the weight. Part of the reason for the Sh.Abs. is that if the bands broke (they never have in 24 years) then the Sh.Abs. stops me hitting the ground !
Pix Explained
I have got myself going.
1 and 2 are the rear suspension: They are probably clearer pictures, which I why I have included them. Both back and front rubber bands are the same apart from width of rubber and number of bands. You can see the clamping device with the spikes sticking through.
3 to 5 are front suspension, and you can see the complications I got myself into with the quadrants.
The rear suspension has 4 (I think) layers on each side of the yoke: So in effect there are 16 layers for each side of the car. The centre distance when not extended is about 5 1/2 inches. In other words the rubber tension is very great, but that is mainly due to the flat angle they are running at. It is easy to adjust, but very time consuming by the time you have measured the wheel rate as I said in the last Email.
The front suspension is not so high geared;but that is a matter of the push rod and quadrant gearing.
The moving away from individual bands to one long strip each side of the yokes with the spiked clamps was one of the best things I did for alterability.
Barry
1 and 2 are the rear suspension: They are probably clearer pictures, which I why I have included them. Both back and front rubber bands are the same apart from width of rubber and number of bands. You can see the clamping device with the spikes sticking through.
3 to 5 are front suspension, and you can see the complications I got myself into with the quadrants.
The rear suspension has 4 (I think) layers on each side of the yoke: So in effect there are 16 layers for each side of the car. The centre distance when not extended is about 5 1/2 inches. In other words the rubber tension is very great, but that is mainly due to the flat angle they are running at. It is easy to adjust, but very time consuming by the time you have measured the wheel rate as I said in the last Email.
The front suspension is not so high geared;but that is a matter of the push rod and quadrant gearing.
The moving away from individual bands to one long strip each side of the yokes with the spiked clamps was one of the best things I did for alterability.
Barry
Rev Barry's Intro
Let me just reply to this before I take some photos.
I use Pirelli Extraflex (I think !). I use 1, 1 1/2, and 2 in. wide. (I do not use 1in now).
As the years go by the rubber stiffens up quite a bit; tho' in initial setting up it stretched for a while in use.
I mount the bands in multiples of 2 with a double yoke which has a centre piece for the pull rods. See the pictures when they arrive.
I think Alan's diagram in his book is 'iffy' when he outs the bands round a pivot, even with needle race inside. I have always put my rubbers in straight pull.
I try to get round the rising rate characteristic when working out my wheel rate by sitting that end of the car on bathroom scales, pulling it down 1/2 in, then lifting it 1/2 in, and I assume (!!!) that the difference in the scales is more or less the lb/in figure, obviously divided by 2 for each wheel.
Originally I got multiple bands sewn in about 1/8 in increments: Now I put a single loop in one end and wrap it round the two pivots and lock it with clamping spikes.
If you take a single loop and pull it down against scales you will see the curve; my own guess work is not to stretch it more than 50% on the car.
My weakness is that I still use shock absorbers and the quadrants etc. add to the weight. Part of the reason for the Sh.Abs. is that if the bands broke (they never have in 24 years) then the Sh.Abs. stops me hitting the ground !
I will send this for now without any photos as the chaos in changing engines since the weekend makes photos awkward to do anything about. Thus much of what I have said will not become clear for a day or so !
Barry Whitehead.
I use Pirelli Extraflex (I think !). I use 1, 1 1/2, and 2 in. wide. (I do not use 1in now).
As the years go by the rubber stiffens up quite a bit; tho' in initial setting up it stretched for a while in use.
I mount the bands in multiples of 2 with a double yoke which has a centre piece for the pull rods. See the pictures when they arrive.
I think Alan's diagram in his book is 'iffy' when he outs the bands round a pivot, even with needle race inside. I have always put my rubbers in straight pull.
I try to get round the rising rate characteristic when working out my wheel rate by sitting that end of the car on bathroom scales, pulling it down 1/2 in, then lifting it 1/2 in, and I assume (!!!) that the difference in the scales is more or less the lb/in figure, obviously divided by 2 for each wheel.
Originally I got multiple bands sewn in about 1/8 in increments: Now I put a single loop in one end and wrap it round the two pivots and lock it with clamping spikes.
If you take a single loop and pull it down against scales you will see the curve; my own guess work is not to stretch it more than 50% on the car.
My weakness is that I still use shock absorbers and the quadrants etc. add to the weight. Part of the reason for the Sh.Abs. is that if the bands broke (they never have in 24 years) then the Sh.Abs. stops me hitting the ground !
I will send this for now without any photos as the chaos in changing engines since the weekend makes photos awkward to do anything about. Thus much of what I have said will not become clear for a day or so !
Barry Whitehead.
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