Help on Leading link

["HIGH TOWER"]

Ok I have a V8 rover auto trike hooked up to a jag irs rear,Fantastic its an old build but it was the right price . And goes , the problem the front end . think it needs a leading link . How do I calculate what coil over damper to use. its a long machine ,4 metres.passenger weight of 35/40 stone .The plan was to try two reliant front springs ?.tack them on and see what it looks like.any advice or ideas greatly appreciated.

[Reliantman]

Hightower.
Chris Ireland used to use Reliant shocks on the front of his v8 trikes and they handled ok.

Cheers.Doug

[Blackjack]

Weigh the front end. That's the weight the spring has to support. Call it 400 lbs.

Suspension should sag about 1" to an 1 1/2" at rest. Lets stick with an 1".

Two springs so 1/2 the weight to get a load for each shock. 200 lbs. divide by the "sag" gives you 200lbs/in. This is the HARDEST spring you will ever need or wnat in that application, and would install very easily with just enough compression to hold it on the seats (allowing for settling in the spring).

If you were to use a 100 lbs/in spring that required compressing by 1" to fit the shock it would exert a static load of 100 lbs on the seat. When fitted it would still sag by 1" as the total compression in the spring is then 2" which means it is exerting the 200 lbs on the spring seat.

A 67 lb/in spring compressed by 2" would give 134 lbs of static load and sag 1" when the 200 lb load was applied (200 lbs - 134 lbs = 66 lbs so slightly under 1" but close enough).

If the ratio between shock movement and wheel movement isn't 1:1 you need to factor that in as well.

The stiffness of the damping will affect spring choice too.

What you actually choose is going to depend on the available travel, whther you want a pimp mobile ride or something a little sportier. But I have to point out that be they Vauxhall or MacLaren most initial choices get altered even when the whole thing was designed on a computer.

I tend to buy AVO units off of Merlin Motorsport as you can get a huge range of springs at about £20 each, and they have adjustable damping and preload at a cost of about £100 each including the spring of your choice. They also come in a load of different sizes.

[dracken1]

errrr yea what blackjack said ;)

just one thing

its a long machine ,4 metres.passenger weight of 35/40 stone

wow thats a heavy passenger how much do you weigh :D

[Blackjack]

I seem to recall that Chris Ireland mounted his shocks in FRONT of the spindle.

This reduces the wheel rate and effectively gives you softer springing.

If you used a pair of Reliant shocks behind the spindle then it would be significantly stiffer. Maybe to the point where the wheel doesn't follow the road surface (which is kind of the point of suspension).

And look Dracken, I left all the long words out and I never mentioned wheel frequencies once, what more do you want????? :confused: :confused: :confused: :p

["HIGH TOWER"]

Been away for a few days and come home to this .thanks people ,certainly given me some food for thought.looks like its time to get the old abercaus out and have a guess. Just to let you guys know ,yes it is 4 metres long . jag IRS on the rear. 3 and a half litre auto box , For thos intrested I stoped looking at how much I weigh when I passed 25 stone. If you want to ask my wife good luck ,but you better have your skid lid on. But there is the camping gear as well,total WELL over 40 stone. all hanging on that front end. still in the look see mode at the moment . but thanks again for the posts. SHAUN. :cool:

[triker_gal]

Hope you had a good holiday and a great Birthday matey xx Oh and yes you can have my babies, but i can't remember where i left them......LOL

[STEG]

HIU Ria hope you dont stay locked in that coffin to long,lol you was out of it on saturday and it was great seeing you again XXX

[triker_gal]

Hiya Steg. I'm out of the coffin for now, till after a phone call tomorrow morning, then who knows. ;)

["HIGH TOWER"]

Lots of folks asking after you hope things work out are you going to show at BOF next weekend .Me and the boys coming in numbers . :cool:

[triker_gal]

Well done the phone call, not out of the woods quite yet. I'm coming to the BOF'S but think it will only be for the day on Saturday, but dont worry, i'll be looking for ya xx :D

["HIGH TOWER"]

will try and stay uprite till you show at least. :cool:

[skidlid sid]

Weigh the front end. That's the weight the spring has to support. Call it 400 lbs.

Suspension should sag about 1" to an 1 1/2" at rest. Lets stick with an 1".

Two springs so 1/2 the weight to get a load for each shock. 200 lbs. divide by the "sag" gives you 200lbs/in. This is the HARDEST spring you will ever need or wnat in that application, and would install very easily with just enough compression to hold it on the seats (allowing for settling in the spring).

If you were to use a 100 lbs/in spring that required compressing by 1" to fit the shock it would exert a static load of 100 lbs on the seat. When fitted it would still sag by 1" as the total compression in the spring is then 2" which means it is exerting the 200 lbs on the spring seat.

A 67 lb/in spring compressed by 2" would give 134 lbs of static load and sag 1" when the 200 lb load was applied (200 lbs - 134 lbs = 66 lbs so slightly under 1" but close enough).

If the ratio between shock movement and wheel movement isn't 1:1 you need to factor that in as well.

The stiffness of the damping will affect spring choice too.

What you actually choose is going to depend on the available travel, whther you want a pimp mobile ride or something a little sportier. But I have to point out that be they Vauxhall or MacLaren most initial choices get altered even when the whole thing was designed on a computer.

I tend to buy AVO units off of Merlin Motorsport as you can get a huge range of springs at about £20 each, and they have adjustable damping and preload at a cost of about £100 each including the spring of your choice. They also come in a load of different sizes.


Would that work on the rear?

Im trying to work out what spring rate i would need for my IRS on my trike.

[Blackjack]

Short answer is yeah.

IRS is a little different in that you need to weigh each wheel and base your choice on the average corner weight, but the basic principles the same.

There are a few more complexities such as whether you are going to get some roll stiffness from an anti-roll bar or the spring rate.

If you really want to get into it, then Alan staniforth's book Competition Car Suspension is a good source of information (ISBN 0-85429-645-X) mine was £19.95 but that was a few years ago. Staniforth's "Race and Rally Car Source Book" is another useful thing to have about as that covers suspension (in less depth) and all sorts of other useful stuff.

You need to actually understand what he's talking about and apply it to your situation (trikes being different from cars) but it will probably save you the £20 somewhere down the line.

["HIGH TOWER"]

Well guys now we are talking rear ends ,see if ya can help me out. My trike has a IRS rear ,straight out of a jag in board disc brakes etc. works a treat , 100% better than the hard tail i have just sold. but the main body rolls out on courners ?. any way i can stop this with out giving up thos loverly springs. its not a hudge roll just a few degrees .I can live with it ,but was thinking anti roll bar ??. :cool:

[Blackjack]

Basically what an anti roll bar does is reduce the "I" part of the IRS. You're tying the two independent sides together with a torsion bar.

Whilst this will reduce the roll, there is going to be some loss of ride quality.

There are other things to look at such as lowering the CofG and raising the rear roll centre, but these aren't always practical.

Briefly, the front roll centre is where the tyre touches the ground (well it is on a trike anyway), the rear one will move around with the suspension travel. A line that connects the two roll centres is the roll axis. The higher the CofG is above the roll axis the more roll you will experience. Lower the CofG you get less roll, raise the roll axis you get less roll. Though there are problems with on the limit behaviour if they get too close together, the vehicle tends to lose adhesion with little or no warning. Not pleasant.

I think both the books I mentioned above deal with building adjustable anti roll bars (which seems to me to be an eminently sensible idea.) and plotting the instantaneous roll centre. Though apparently you need a lot of string................

["HIGH TOWER"]

thanks for that black jack ,having just up graded from a hard tail trike to this monster .i will live with the fantastic springs,gives us a really smooth ride .and no back problems,thanks any way :cool:

[skidlid sid]

Must admit i was thinking of a antiroll bar my self until i jumped up and down and rocked side to side on a Trike Shop built trike.
They use a pair of CBR600 mono shocks and a anti roll bar not alot of movement up and down but still rocked side to side, so im thinking anti roll bars are a waste of time.

[Blackjack]

Not entirely true.

the most important thing is to get the geometry of the arms right, followed by the spring rate, followed by the anti roll bar rate.

Suffice to say that everything everybody knows about suspension arm geometry doesn't apply to trike rear ends.

IRS trikes actually handle worse than rigid ones. IRS may ride better and give better road holding, but the actual handling is not a patch on a rigid trike.

Next time I have the Metro thingy running, any one brave enough to come and try it out is welcome to do so (it's already destroyed one car without sustaining any serious damage). Mostly because it's easy to talk a load of crap about stuff like this, but a practical demonstraton tends to go a lot further than all the theory in the world.

Shame it's not a manual any more, as it was kind of fun demonstrating how to wheelie something that you'd specifically designed not to. Though, thinking about it...........

Maybe I'll build just one more, this time with a turbo 1600 K series and no anti wheelie mod..........

[skidlid sid]

I agree with you there about ridgid trikes handleing better, only problem is they tend to pick a wheel up round tight corners if you are going in abit to fast.

On the subject of spring rates just tried a pair of 550lbs springs but still to soggy.

Gonna try and find out what spring rate CBR600 monoshocks use.

[Blackjack]

I agree with you there about ridgid trikes handleing better, only problem is they tend to pick a wheel up round tight corners if you are going in abit to fast.

On the subject of spring rates just tried a pair of 550lbs springs but still to soggy.

Gonna try and find out what spring rate CBR600 monoshocks use.


As for picking a rear wheel up, that's why you don't want a limited slip diff, as with a convetional diff once it picks a wheel up it can only slow down unless you're going down a very steep hill. This is nice as it makes it difficult to turn the trike over.......

As for the springs, unless you put a set of scales (or even two and add both the wieghts up) under the wheel and find out what the actual weight on the corner is, you're just going to be making uninformed guesses. if you weigh it you can make informed guesses.

[skidlid sid]

I took both shocks of today and let the back end down on the bathroom scales and it weighed 120kgs which is 264lbs.

When you say weigh each corner, like put the scales under each wheel, isn't that weighing alot of unsprung weight like the wheel/wheel hub/disc/caliper and wishbones?

Sorry to keep going on about this.

[Blackjack]

If you put the trike on a weighbridge with all three wheels on there you get the total weight. By putting a set of scales under each wheel you get the corner weight, the total of the corner weights will be the total weight

On the other hand, if you put some chocks under the frame and the scales under the wheel with the shocks off then you get the unsprung weight. This is because the sprung part of the weight is supported by the chocks. Unsprung weight isn't that important in this case.

To get some meaningful figures for working out the spring rate you need the corner weights. This is because the with an IRS set up you basically have a spring at each corner.

If you're really finicky you could use the corner weight less the unspring weight.