Marlin trails car

[AndrewKB]

Re: Marlin trails car

See my posting #3 above first.

I know people who've had new springs for Marlins made by both https://www.jones-springs.co.uk/ and http://www.owensprings.co.uk/ - some have worked OK, some have failed very early, and there seems to be little consistency. But … I don't know the exact specification that the various people asked for. I also know someone who's fitted modified Ford P100 pickup springs, but he 'lost' me when explaining the mods necessary to get them to work (we were in a muddy forest at the time). And, of course, it all depends on how much weight (toolbox + tools + spare wheels + ballast + etc.) that you're carrying. I suspect that very few triallers actually know the total weight that they're carrying. They may know how much ballast they've added, but I bet they don't know the weight of all the other bits (I don't).

One idea, which I haven't yet investigated properly, is to get a set of 10cwt van springs made with extra 'set' to increase the ride height when loaded. That may mean an increase in the length of the top leaf but, otherwise, the overall spec stays the same. It's worth discussing your options with Jones who are, I believe, more likely than Owen to know the original 10cwct van spec,

[newtrialer]

Re: Marlin trails car

I am working on this as well, I am pretty sure I have the van axle, and the springs on the car when I bought it were stripped down to the 2 longest leaves only. Now I have begun to get the rear weight where I think it needs to be (about 200kg ) I have ordered from Kev at jones springs a new set of springs made to vanspec. Kev is brilliant and really knowledgable. My current spring travel when loaded is about 70mm. I am hoping to get this well over 100mm with stiffer springs and then am looking to extend the rear links and steepen axle wedges to get some more height.

I have wound up the trunion torsion bar adjusters as well to get some more front height. That worked. 20mm at adjuster gave about 40 mm at wheel. Well worth it.

long term I am thinking Sierra indespension at the rear. But not sure if I would get evicted from MOC for straying too far .......

[duncan]

Re: Marlin trails car

If you take the torsion bars apart you will find the bar that you adjust is attached to the actual torsion bar on splines so you can get as much adjustment as you want by moving around a number of splines - the adjustment bar is the fine tuning

[newtrialer]

Re: Marlin trails car

Ahh, every days a school day, thank you.

[AndrewKB]

Re: Marlin trails car

Two more points … (1) If you plan to use extended rear spring hangers, then you should consider a Panhard Rod to keep everything located properly. But I'm not convinced that the extra height is really worth it. It doesn't change the height of the diff, which is where ground clearance is at its lowest. (2) Sierra independent suspension will take you out of Class 7, and you don't want that.

[gerryrichards]

Re: Marlin trails car

Interesting thread this so thought I'd weigh in with some thoughts. As a new Marlin owner who plans to do some trials this is interesting to me. To my mind there are 3 main factors at play with the rear springs where trialling is concerned : 1. ground clearance 2. spring rate 3. spring strength. Note that 2 and 3 aren't necessarily related as surely a spring with a lower rate can still be 'stronger' (i.e. resistant to failure) than a stiffer spring, due to its design and materials used etc.

In general chassis design the rule of thumb is that where more grip is needed due to a less grippy surface (e.g. when it starts to rain) then a softer spring is a good thing. This is the same reason that lowering tyre pressures in the rain can help (tyres are undamped springs) and also that you would soften the front of a car which is tending towards understeer and vice versa.

Hence, my thinking is that trailing requires softer springs at the driven end (i.e the rear springs) as opposed to firmer - but with a high damping rate to control the bumps and keep the wheels in contact with the ground. So fitting 'stronger' but also higher rated van springs seems to be the opposite of that. If I have some springs made I'll need to make sure they're 'strong' in terms of robustness to survive a trial, but not necessarily a high spring rate. Bear in mind though that extra weight at the rear reduces effective spring rate so this would need to be taken into account.

Also a lower spring rate means more deflection under load, and it's important to ensure that ground clearance is preserved with a trails car with a heavily loaded rear end. Hence a softer rear spring would need a sufficiently high unloaded stance to account for this extra deflection under load.

So I'm thinking about commissioning a pair of rear leaf springs with a relatively modest spring rate, but still strong enough to survive trialling (high spec steel) and then making sure they give the right ground clearance at the back of a fully loaded trials car (I have a set of corner weight scales so can measure this). Then pair these with a set of adjustable rear dampers and expect to use a high damper rate.

Does that sound like a good solution for rear springs for a trials Marlin?

[duncan]

Re: Marlin trails car

All sounds good
But with leaf springs you can effectively get a variable spring rate - so having a low rate "operating" and a high rate when its compressed a bit is possible

If you visualise a setup where you are using the single leaf - but when it deforms enough it starts to use the other leaves in the stack
Would look a bit weird as when lightly loaded there would be a gap between the ends of the leaves

[gerryrichards]

Re: Marlin trails car

Yes good point about leaf springs having that progressive effect - might be useful to exploit that.

[AndrewKB]

Re: Marlin trails car

In reply to Post #21 ... what you say is correct in theory, but read my Post #16 above. I think the jury's still out on the 'best' spec for new springs for trialling. If you have a set of van springs, fit them first, do a few events, and then decide if they need 'improvement'.

As a general comment ... far too many people who are new to trialling (and not just those in Marlins) theorise far too much when building a trials car from scratch or modifying a road car for trials. There is absolutely no substitute for doing events, seeing what works for you and what doesn't, and moving-on from there. Most successful trials cars have been progressively modified over many years. But ... the major issue with a Marlin is to save weight and make sure that what weight you have is in the right place: no rollbars, no heaters, no additional lights, minimal interior, battery in the back not the front, you get the idea.

[gerryrichards]

Re: Marlin trails car

Sound advice thanks. I've some experience of trialling in Imps, Beetles and my late father's Singer 9hp, but never in a Marlin....

Having said that the last long distance trial that I drove was the 1996 Edinburgh in my very standard 1300cc Beetle. I remember another Beetle driver making the same comment about weight and I followed his advice of only taking one spare wheel, but it was in its original place up front as I didn't get around to building a rear rack for it. We just raised the rear suspension by one spline and fitted a sump guard and off we went. It was a dry day and I had a great navigator/bouncer so we managed to clean everything except Bamford where we ran out of grunt (and driver experience...)

Of course the rear engine was a huge factor with the Beetle but we only had about 45 bhp in an 800kg car, so my 2 litre pinto Marlin should have over twice the power/weight ratio - so the main priority is to move as much weight backwards as possible.... Interesting that you advise against a rear roll bar as it seems quite a few trials Marlins have them and at least the weight is in the right area. My car's interior is very 'workmanlike' already but I'd like to keep my heater, especially if I do the Exeter in January!

But yes, overall I couldn't agree more - try not to over-think it too much, enter an event and go from there...

Cheers

Gerry

[magicmalkin]

Re: Marlin trails car

Tips please on fitting hydraulic handbrake

[stevejgreen]

Re: Marlin trails car

Tips please on fitting hydraulic handbrake

In the first instance they will not pass an IVA or MOT unless you have a mechanical system as well

I would have thought that drum brakes would be unsuitable, disk brakes, where a second set of calipers could be fitted would be a better starting point.
MGF use the same PCD as a standard Marina axle, so a good starting point.

Read the relevant trials regulations for guidance.