Escort Sigma 1600 Race Car

[Roadsport]

Re: Escort Sigma 1600 Race Car

Fabulous write up Markus...what a brilliant result....in several ways......well done mate!

Thank you Rich ! Thats very kind of you. Now I do have some tinkering to do before the next event.

At the moment I've ordered in some spherical rod ends(?) to manufacture new 4 link bars. Been offered a good second hand prop and I'm debaiting with the scruteneers do I need to change the windscreen or not. If so I will have a heated screen made for the car.

[Roadsport]

Re: Escort Sigma 1600 Race Car

Markus,

Lower bars work in compression when launching the car. When calculating my rear end I found the compression load on lower arm is around 900kg (OK it depends on engine power, link attachment distance from axle centerline, rear ratio etc but generally the load should be not very far from that figure) - so if you had some imperfection in one of your lower arms, slight bend or kink maybe, it could have failed in the violent launch and then the other would follow immediately because it could not hold the double force.

I do agree with you. That makes sense to me. I did extend the lower bars by an inch. I cut the original bar inserted a tube inde and weded it on. The welds and the extension held but it may be the rods could no longer take the load. Well I suppose that pretty obvius now.

[Roadsport]

Re: Escort Sigma 1600 Race Car

Good result, considering.
At least the engine is still in one piece anyway... unlike the propshaft
Well done for sticking at it, and look forward to the next race.

Dave

Thanks Dave I am very pleased with the end result too. I wouldn't mind it coming to me a bit esier though.

The next race is the main event of the seson. It is the biggest circuit racing event in Finland with 200 or so cars participating annually. It attracts the fastest drivers and cars to the grids so if I dream of a
podium finnish I relaly have my work cut out for me. But I will not enter the race with defeat mentality. Hopefully I now have time to be more prepared for the race.

[Roadsport]

Re: Escort Sigma 1600 Race Car

Some bits and bobs for the new 4 link bars. Holy S*it these joints are expensive . I'll buy some 25mm dia seamless tube with 3mm wall next week and then its on to

[Roadsport]

Re: Escort Sigma 1600 Race Car

For no reason really

[Roadsport]

Re: Escort Sigma 1600 Race Car

Some bits and bobs for the new 4 link bars. Holy S*it these joints are expensive . I'll buy some 25mm dia seamless tube with 3mm wall next week and then its on to

Except that I forgot to order the locking nuts

No trouble finding the 5/8" UNF nuts but the 16x2 lefthanded thread nut could prove to be a pain in the ...

[david_white]

Re: Escort Sigma 1600 Race Car

Been reading your updates with fingers crossed for the new engine and after reading the excellent write ups it sounds like you've done a great job of getting it all back together and peddling it hard. Great result

That prop is a weird one but I have seen those same ones break before and they do go with a bang. Hopefully you wont have that problem again and the link bars will be bit stronger too

[FOSSIE]

Re: Escort Sigma 1600 Race Car

Some bits and bobs for the new 4 link bars. Holy S*it these joints are expensive . I'll buy some 25mm dia seamless tube with 3mm wall next week and then its on to

Are you going to use rosejoints on both ends of each link bar?

[rustang]

Re: Escort Sigma 1600 Race Car

The next race is the main event of the seson..

I am seriously considering making a trip to the Ahvenisto Grand Race this year. I will let you know if I have booked my ferry tickets!

[Roadsport]

Re: Escort Sigma 1600 Race Car

Are you going to use rosejoints on both ends of each link bar?

Yes. I never really liked them bushes in the body end of the bars. Don't like the way they resist movement when tightened. So after hearing some pros and cons about double rose jointed link bars I decided to give them a go.
I always thought the bushing was pretty much mandatory but now know some have got away with rose jointing the bars at both ends. I have had my link bar bushes replaced with nylon ones so propably have had pretty much zero flex in them allready.

[Roadsport]

Re: Escort Sigma 1600 Race Car

I am seriously considering making a trip to the Ahvenisto Grand Race this year. I will let you know if I have booked my ferry tickets!

It's my favourite motorsport ebent in finlnad. The WRC rally finland is second and the Europan HIstoric rally in Lahti is third.
This year the last two are combined though.

[Roadsport]

Re: Escort Sigma 1600 Race Car

Been reading your updates with fingers crossed for the new engine and after reading the excellent write ups it sounds like you've done a great job of getting it all back together and peddling it hard. Great result

That prop is a weird one but I have seen those same ones break before and they do go with a bang. Hopefully you wont have that problem again and the link bars will be bit stronger too

The bars will deffo be stronger Just hope the link box will hold.

[FOSSIE]

Re: Escort Sigma 1600 Race Car

I understand your theory, and I agree mostly, but it worries me using ALL rosejoints. That way, you have absolutely no flex/give in the system. Unless your link bars, from pivot to pivot are all exactly the same length, you will find them fighting each other as the axle goes through it's travel under load. With no flex, you have to rely on elasticity of the steel, which means putting massive stress on the bars, rosejoints, and importantly - the bolts. I've seen several cases of 4-link bolts breaking on all-rosejoint systems, which we ended up putting down to not having any flex in the system.

Just replacing the rosejoint with something slightly more flexible on 1 end of 1 bar would be enough.

I love the car by the way - and love what you did with the axle

[Roadsport]

Re: Escort Sigma 1600 Race Car

I understand your theory, and I agree mostly, but it worries me using ALL rosejoints. That way, you have absolutely no flex/give in the system. Unless your link bars, from pivot to pivot are all exactly the same length, you will find them fighting each other as the axle goes through it's travel under load. With no flex, you have to rely on elasticity of the steel, which means putting massive stress on the bars, rosejoints, and importantly - the bolts. I've seen several cases of 4-link bolts breaking on all-rosejoint systems, which we ended up putting down to not having any flex in the system.

Just replacing the rosejoint with something slightly more flexible on 1 end of 1 bar would be enough.

I love the car by the way - and love what you did with the axle

Thank you for the compliments! That means alot coming from a professional! The axle is some what rare in an mk1 as it is an US hybrid 7.5" / 9" with group 1 half shaft flanges.

On what kind of cars and conditions did the bolt failure occur? On track with slicks or in rally on jumps or collisions?

To be perfectly honest with you I'm a bit worried too. But I am too curious to no to go trough with this.
The lack of flex is the thing to worry about. There is a reason why (almost) everybody uses bushing in the front of the link bars. And no, my link bars will not be tyhe eaxact lenght since everything is hand made so the tolerances are a bit on the large side.
I'm hoping the purpose built collets will help to ease the stress on the front bolts. And to spread the load across the lenght of the bolt rather than just pushing it from the middle as would be the case using mere spacers to center the rose joint. This is why I chose to use bigger rose joint on in the front.
But the poor bolts on the axle side will have their work cut out for them. As will the DIY link bar brackets.
But how much can the all nylon bushing flex? I assumed their used to eliminate all flex and play? If that is the case then I'm not too worried about the axle side link bar bolts since they've worked for me for ten years now.

Check back to this thread every now and again and you me well get an " I told you so" - moment

[rustang]

Re: Escort Sigma 1600 Race Car

You can always check the free movement of the axle with dampers and springs removed, put the car on jackstands, support the rear from the center pumpkin in different heights and rock one end of the axle up-and-down, you should feel if there is any significant bind. If there is, something will develop fatique cracks and fail.
My own 3-link+phb full uniball setup articulates through all suspension travel without any resistance, maybe you could consider using this system - just add one bracket to the rear axle on top of the pumpkin and do a little modification to the propshaft tunnel "under rear seat" to make the body-side attachment point to the single upper link.
Latest Mustang GT which kicks BMW M3-s ass around racetrack has similar 3-link setup