dozracing
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| posted on 6/10/03 at 08:46 PM |
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Forgot to say, that i have developed new valving and sizes for IRS and De Dion cars and Sierra based cars. Primarily because i'm going to be
launching a Sierra based single doner car that has IRS and or Dedion as an option.
If you want to play games with ride height then of course you can with mine, and if you want super cheap no frills you can have mine in the non
adjustable (ride hieght) form for £180.
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Mark Allanson
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| posted on 6/10/03 at 08:54 PM |
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Questions
1, What is the logarithmic curve of the rebound structure on the alloy content in the springs, and does the velocity of the damping fluid through the
valve reach a harmonic with the vortex around the body of the damper once you reach geostationary orbit?
2, Do they drive good
(Don't bother replying to question 1!)
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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craig1410
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| posted on 6/10/03 at 09:24 PM |
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Mark,
the sad thing is that I got half way through your sentence in (1) above before I realised it was a pi$$ take... Doh!
Doz,
I'd be interested in a good general description of how they work and how you match spring characteristics with the damper characteristics. Also,
practical stuff like how do you determine the best ride height point as a point between max bump and rebound. I would basically like the "black
magic" to be lifted from the subject so that we can all make informed decisions about the damper characteristics rather than relying on other
people who may or may not know what they are talking about and in any case a rarely building exactly the same car anyway. As an example, I know how
camshafts work and could fairly intelligently order a Cam to suit a particular engine and usage. I can't yet do the same for a damper and
spring.
By the way, do you know when the 3rd edition is due out?
I hope this helps,
Craig.
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JoelP
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| posted on 6/10/03 at 09:32 PM |
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i got as far as harmonics before i realised! reminded me of that line in hitchhikers guide about eddies in the space time continuum. whats he doing
there? anyway...
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pbura
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| posted on 7/10/03 at 01:02 AM |
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quote:
Originally posted by dozracing
At the end of the day my shocks are to be the officially recommended shock kit in the 3rd edition of the book.
Good for you, Darren! 
Dampening is a fairly black art. Thinking about your article, maybe you could explain how the sprung mass of the car and the stiffness of the spring
combine to set up a frequency of oscillation. The job of the shocks is then to dampen that oscillation within, say, one cycle under most
circumstances.
Also, the shock itself can act like a spring in certain transient situations, like sharp braking or hitting a road shock. This feature can be used to
tune a car's handling, by shifting weight to the rear of the car under heavy braking to improve ability to accelerate out of a corner.
So, a shock must be compatible with a car's weight and springing, and unsprung mass is probably important, too. How does a driver pick a shock
that will accomplish his objectives? That would be a good question to answer in your article. 
Or you could answer Mark's questions 
You've got to admit that there's a leap of faith involved in buying non-adjustables for a one-off car. Nonetheless, if my car turns out
with compatible weight and springing, your shocks are going to be VERY hard to pass by.
Best of luck,
Pete
P.S. I guess I wrote a little mini-tech article here, for the benefit of readers who may be learning about the function of shocks. My knowledge ends
right there, though. How the heck do you spec a shock to go with that?
Just for a laugh, once I saw someone selling these on eBay as a Locost coilover:
http://www.surpluscenter.com/item.asp?UID=2003030810355745&catname=&qty=1&item=28-1342
Let's see you beat that, Darren
[Edited on 7/10/03 by pbura]
Pete
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Stu16v
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| posted on 7/10/03 at 01:25 AM |
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quote:
There is also a substantial section in there that details a test session where all the main suppliers products were tested (including AVO two way
aluminium bodied) back to back using an experienced test driver. The results are published in the book, and all i will say is that i wouldn't
make mention of it if mine hadn't come out very well in the results.
As a matter of interest, what was the spec of the car tested?
Dont just build it.....make it!
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JoelP
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| posted on 7/10/03 at 08:02 AM |
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quote:
Originally posted by pbura
Just for a laugh, once I saw someone selling these on eBay as a Locost coilover:
http://www.surpluscenter.com/item.asp?UID=2003030810355745&catname=&qty=1&item=28-1342
Let's see you beat that, Darren
why the hell are they so cheap? thats less than £15. and the spring rate is near enough right innit?
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pbura
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| posted on 7/10/03 at 10:22 AM |
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quote:
Originally posted by JoelP
why the hell are they so cheap? thats less than £15. and the spring rate is near enough right innit?
For the front of the car, they're way too weak, and a bit long. For the back, they're slightly heavy. They're tempting at that
price, but springs and shocks are the #1 factor in how the car is going to ride and handle, and worth getting right. Cheap springs are going to sag,
and cheap shocks are going to damp inconsistently, possibly overheat, and wear out prematurely.
I wish I had that eBay ad, because it was a hoot. The seller was portraying them as real sporting kit.
Some guys in the States are using them to test with, and maybe some are using them on their cars, too. I was thinking of getting some for temporary
use, but decided to just use drilled 1" tube.
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DAMPERTECH
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| posted on 8/10/03 at 05:02 PM |
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I HAVE BEEN ASKED BY SEVERAL PEOPLE TO VIEW THIS FORUM TO CHECK THE ON GOING SAGA OF THE DAMPERS.
I HAVE WORKED IN DAMPER FOR OVER 30 YEARS. I DONT WANT TO SOUND BIG HEADED BUT THERE IS NOT ALOT I DONT KNOW ABOUT THIS SUBJECT. I AM THEREFORE REALLY
LOOKING FORWARD TO DARRENS FORTH COMING ARTICLE. MAKE SURE IT IS FACT AND NOT BULL S**T AS I WILL SCRUTINISE EVERY WORD.
AS I AM HERE I MIGHT AS WELL REMIND YOU THAT I CAN DO A SET OF GAZ SPRING AND DAMPER £250 INC AND YOU CAN HAVE ANY SPRING RATE YOU WANT.
P/S DARREN YOU DON’T KNOW HOW MUCH I PAY FOR MY DAMPERS BUT THEN AGAIN I WILL NEVER WORK WITH M .SCHUMACHER !!!
IF YOU ARE LOOKING FOR A FIXED RATE DAMPER TO YOUR SPEC I CAN DO THEM AT A £10 EACH FROM OE MANUFACTURERS.
THE NUMBER TO RING IS 01709 703992
BEST REGARDS,
DAVE
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dozracing
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| posted on 8/10/03 at 07:57 PM |
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For those of you interested in the maths behind shocks you'll find a paper written by A G Thompson enlightening. Its a simple formula for
optimum damping. Not simple to most people as it takes up the width of the A4 sheet, but, its simple in comparison to the 8 pages of A4 that my
formula took up when i did my final year degree project on 4 degree of freedom car model. As you all will know a single degree of freedom model with
damping gives you a polynomial equation to solve. A two degree of freedom model gives you a polynomial equation to the power 4, a 4 degree of freedom
model takes this up to a power of 16 thats where the 8 pages of equation come in. We should all remember from A level maths, or degree first year how
to derive a polynomial equation, but, it takes a series amount of computing power to solve one to the power of 16. Basically this is what you start to
get into if you want be able to calculate the optimum damping for a car. The problem is that it then only calculates the coefficient of damping you
want, and doesn't tell you how to split that between bump and rebound or how to arrange the low and high speed characteristics either.
But for our current argument on the requirement for fixed or adjustable rate dampers to take into account build variations due to engine mass it will
be good enough. I'll post another reply later with mathematical results of a spec. car and then one with variations of plus or minus say 20%
front sprung mass. Then we'll see what the percentage difference is in the damping requirement and you can all then make a judgement as to
whether my fixed rate shocks can be expected to work well on a range of different builds. Dave can tell us what the percentage change is per click of
adjustment on the Gaz and we can decide what extent of the range of adjustment on the Gaz's is useful to us Locosters. That has to be fair, let
the numbers do the taking not the bull shit.
Syd. If you want to read my previous texts you need to get a back copy of Racecar Engineering that includes my article on the blow off valved damper
that we developed for touring car races so they could kerb hop more aggressively. Or a back copy of Race Tech where there was an article on the
fundamentals of High performance gas mono dampers. You could also try getting aback copy of the 750MC bulletin where i described how to setup a
racecars shocks and tune them and cure handling problems. If thats nmot enough you could perhaps read the book on racecar springs and dampers
published by RaceTech on which myself and a colleague contributed. You might also be interested in another RaceTech article that featured an article
about the Lateral Acceleration Sensitive Damper i invented. There may be other articles in various mags about things like the 4 post test rig that we
designed and developed in house.
Also in the States there are several articles describing the suspension system we designed for the Shelby Series One car.
The last time i spoke with Martin Keenan, was when he called me to discuss me supplying him with shocks for all the Indy's. He insisted that he
wanted to only sell adjustable shocks. I'm not sure why as he has a car thats well sorted for fixed rate ones! Any way i suggested he go for
Gaz's. His reponse was that he had been using them for a long time as a regular supplier to the Indy, but, had fallen out with them over issues
that i didn't ask about and wanted desperately to find any other source of dampers apart from Gaz. Not sure what his current situation is, as
the kit car mags all carry ads for Gaz's but i believe he moved on to Rod Avons (AVOn) new damper company, Protech. Protech have launched an all
ally damper with improved valving and adjustment mechanism (with a little help from their friends no doubt) with the express desire to force Gaz, and
if possible Avo out of business. No love loss in the damper world i can tell you.
Dave, If you buy an OE shock (bare in mind it has to be valved to suit a Locost which takes development and testing) for £10 fixed rate, add a spring
platform, threaded sleeve and threaded lower platform, anodise them, and stick a spring on it, add VAT, add shipping from the OE manufacturer and a
1/4 of your normal profit margin, you'll end up selling them for £200 a set like me. You should have done that years ago between Nitron and I we
have sold nearly 500 shocks around the world, 300 since last christmas. Not a single return or complaint, apart from a guy who i accidently sent 3
rear shocks to and only 1 front. But, to do that be prepared to put up at least £7000 up front. Now i did it to prove a point and to provide what
Locosters were in need of, a damper of good quality, reliability yet significantly cheaper than the competition. I never set out to do it as a
business, Nitron were doing that, i inherited it. I took it on because of the number of people who were disappointed that Nitron were going to stop
selling them, when they had set their heart on buying a set. As i felt responsible for kicking it off in the first place i took it on.
If you buy a set of transit ball joints from me it actually costs me about 40p. That was a mistake i meant to offer them at cost. If you buy a set of
bodywork from me, i make about £10-£20 if that, i do it to provide work to a great GRP man i know.
My site provides me with nothing more than beer money, but, the Locost community, of which i am one benefits. If i can use my contacts to provide good
quality parts at the lowest possible prices then why shouldn't i pass it on to all the other people who are in the same positon as me, trying to
build a sportscar they otherwise couldn't hope to afford.
Dave, scrutinise the article all you want, they'll be no bull poo in it. And just before you get really upset with me, i would estimate that at
least a dozen of your sales this passed 10 months will have been as a result of me passing interested parties on to you. The reason is that my opinion
is that if you want an adjustable shock for all the right reasons you should be prepared to spend £200 each on them. If you want to cut corners and
have the knob to twiddle then there is nothing to choose from the Gaz, Avo and Spax except that Gazs are by far the cheapest. To me if you must have
the adjustment and really can't find the money then go for the Gaz.
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dozracing
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| posted on 8/10/03 at 08:55 PM |
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Update.
After some quick maths.
20% change in engine weight results in 10% change in natural frequency, and 8% change in damping coefficient.
Now most road cars operate between 0.4 and 0.5 coefficient of damping, thats a band of 20%. So we are well within the band that road car manufacturers
work within.
I'd be interested now to see what the increments are on the adjustable dampers. On fine racing damper adjustments you would have a range of +/-
50% at least in 14 clicks. Thats 7% per click, so not a lot of the range will be used allowing for engine mass difference of 20%.
The difference on race dampers is how you can tune the characteristic (ie where the damping forces are in the speed range) without necessarily
altering the toal amount of damping of for that matter the coefficient of the range of operation. To do this you need individual control over high and
low speed damping in both bump and rebound, and all these must be seperate from one another.
Kind regards,
Darren
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Stu16v
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| posted on 9/10/03 at 09:55 AM |
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quote:
20% change in engine weight results in 10% change in natural frequency, and 8% change in damping coefficient.
So comparing a BEC with an engine weighing approx 85 kg total, with the engine sat quite far back in the engine bay, fitted to a stripped out road
legal racer, is a max 20% different to a V8, (140kg?) fitted further forward in the engine bay, with additional gearbox weight (60kg?), fitted to a
car with steel panels, windscreen, heater, weather gear, full carpets, plush seats, big wheels etc, etc?
This could *possibly* be the difference in weight for just one type of car. I know for a fact that there are Westfields out there that weigh less than
400 kg, and yet there are others touching 750kg. Lets forget about folk building bigger/smaller cars, wider/narrower suspension, differing suspension
unit mounting points, IRS/live axle/dedion, the list is probably endless.
As a rough guesstimate, rather than a 20% difference, realistically you could be looking at as much as 100% difference total car weight between the
two extremes, and possibly an even higher percentage difference per axle.....
And we still havent touched on driver preference!
The discussion continues......
Dont just build it.....make it!
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Metal Hippy
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| posted on 9/10/03 at 10:02 AM |
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Be interesting to see how ours ends up with the hefty Beemer 3.5 six in it...Iron block, alloy head and gearbox...
Not light and very long...
Cock off or cock on. You choose.
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philgregson
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| posted on 9/10/03 at 11:37 AM |
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It's turning into another of those 'who is the cleverest?' arguments.
Surely this is all about compromise.
I would have thought that the entire concept of a locost build is one of compromise. We could all spend tens of thousands of your earth pounds on
exactly the right trick bit for every component but we don't 'cos must of us are trying to build a fun car for not much cash beacuse:
a) We want a good handling fun sports car.
b)We want to do it cheaply.
c)We want to have done it our selves.
Further to this most of us are building cars that deviate relatively little from standard.
Surely if people want to save some money and get their car on the road and just enjoy every day road driving then a fixed rate damper is a perfectly
reasonable compromise considering the other many compromises we have already had to make.
I suspect the reason many people want adjustable dampers is beacuse they think they should and beacuse it is another tick on the spec sheet - not
beacuse they need them. How many people buy adjustable dampers but never adjust them? Loads I suspect.
Just remember we are all individuals building our own thing in our own way and if fixed rate dampers suit some people than that is fair enough as long
as they understand the compromise they are making.
Like I say some of us just want to have fun at a budget price and shouldn't feel pushed into having to play at being racecar engineers by those
who want to do that them selves (or are racecar engineers!).
Garbled I know but just wanted my 2p.
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philgregson
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| posted on 9/10/03 at 11:51 AM |
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Just an afterthought -
Didn't the father of all locosts (and destroyer of many relationships), the great Ron Champion, (May grease be upon him) not just go and buy a
pair of non-descript old coil overs from an autojumble without giving a seconds consideration to bump rebound, or indeed anything else.
We should show our faith in the great locoster and do likewise.
Phil
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craig1410
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| posted on 9/10/03 at 11:58 AM |
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Stu,
I think you are pushing it a bit now matey. 
Most Locosters I expect will be in the 550Kg to 650Kg region with very few below 500Kg's and an unfortunate minority above 700Kg's. Taking
600Kg's as the average (say) the +/-20% rule gives limits of 480 and 720Kg's which will surely cover all but the most extreme examples.
As Darren says, adjustable dampers might have very large increments and very few clicks and unless you know what the variance between clicks is then
how can you hope to set things up correctly? Out of interest did you get a spec sheet with your dampers showing the adjustment factors?
Cheers,
Craig.
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Stu16v
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| posted on 9/10/03 at 12:02 PM |
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quote:
Further to this most of us are building cars that deviate relatively little from standard.
I totally agree with what you are saying, except the quote above. Most of the builders are having to deviate from a 'book' build, not
through choice, but lack of donor vehicles to complete a build. Sierras are probably becoming the most common donor at a guess, and with it drastic
alterations in front and especially rear suspension. Coupled with the fact that a lot also use the donor engine which is markedly heavier than a
Xflow, OR construct a BEC (which obviously is a lot lighter), means that the 'one shock fits all' scenario just wont work. Sure, it will
get the car on the road, and it *may* handle well. All I am trying to say that there is a huge difference between your car and mine, and ideally that
needs to be reflected within the damper.
If not, the suspension is a compromise, one that could be lessened by having at least some adjustment.....
Craig, read Darrens (and ny) post more carefully mate, he quotes a 20% difference, NOT +/- 20%. And I quote EXTREMES....
Makes a big difference to the maths.
HTH Stu.
[Edited on 9/10/03 by Stu16v]
Dont just build it.....make it!
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philgregson
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| posted on 9/10/03 at 12:27 PM |
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I agree that one shock won't fit all but I still contend that the greatest percentage of builds fall within a small standard deviation and that
one shock will still fit many as long as people are aware that it is a compromise and not a 'perfect fit'.
Phil
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JoelP
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| posted on 9/10/03 at 12:40 PM |
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i would also add that on a road car you still get a compromise, ie soft enough for the pot holes and hard enough for good smooth corners. my subaru
wasnt perfect for either, quite stiff on bumps but still more roll then wanted both on constant corners and alternating corners.
i myself would rather have perfect smooth roads, low tyres and NO suspension at all, then atleast the car goes where you point it.
effectivly as i understand it, more weight needs a stronger spring, which then itself requires a stiffer damper to control it. As such its also a
matter of wanting a stiffer spring option, as the spring may be wrong for the car anyway. tuning the damper either way will make the ride more or less
complient but wont make up for the spring rate being wrong.
so really, assuming darrens product gives an acceptable ride in the first place, its the springs we should worry about for different weights.
or is that bull? u tell me...
[Edited on 9/10/03 by JoelP]
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JoelP
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| posted on 9/10/03 at 12:43 PM |
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and as an afterthought, if you know your car will be to either extreme, and think you may need a different spring to darrens standard ones, then you
will need adjustables to cope with the new spring, unless you dont mind a compromise.
most people know roughly what end weight theyre heading for...
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craig1410
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| posted on 9/10/03 at 12:46 PM |
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Stu,
I wasn't reading it like that. If he has designed it for 600Kg's then a 20% variance is either 720Kg's or 480Kg's. If he
designed it for 480Kg's(unlikely) then obviously 720Kg's is +50%
Even +/- 10% on 600Kg's would be 540-660Kg's which would cover most locosts anyway.
Cheers,
Craig.
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stephen_gusterson
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| posted on 9/10/03 at 01:04 PM |
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But what happens when you put your fat girlfriend in it and luggage on the back for a dirty weekend.....Just the passenger weight (approx 70 kilo) is
gonna add 12% or so to an average locost.......
atb
Steve
Relatatively slim, no girfriend, locost compatible wifey
quote:
Originally posted by craig1410
Stu,
I wasn't reading it like that. If he has designed it for 600Kg's then a 20% variance is either 720Kg's or 480Kg's. If he
designed it for 480Kg's(unlikely) then obviously 720Kg's is +50%
Even +/- 10% on 600Kg's would be 540-660Kg's which would cover most locosts anyway.
Cheers,
Craig.
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craig1410
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| posted on 9/10/03 at 10:48 PM |
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Syd,
I'm sure Darren will speak for himself but I would expect, since I am building a de-dion car, that the shock absorber dimensions would be
different for de-dion compared with live axle. Same for IRS. In my case I am making my own de-dion setup so I bought the shocker kits from Darren
before starting to build the suspension around them. However, this did result in a less elegant design than if I had designed the shockers around the
axle.
Just a thought!
By the way Syd, who did you get your shockers from and how much did they cost if you don't mind me asking. Also, are they 'book'
locost size?
Cheers,
Craig.
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craig1410
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| posted on 9/10/03 at 10:54 PM |
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I beg your pardon Syd, he did say new valving as well as new sizes (should have read that before responding really...Doh!)
I guess that unsprung weight might be the other significant difference between IRS Live and De-Dion then eh? That would affect rebound most I'd
expect as there wouldn't be as much unsprung weight to pull the wheel back down. Does that make sense?
Cheers,
Craig.
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