I've got a fug that is currently swing axle and i've picked up an IRS box, trailing arms, hub assemblys etc.

So when i take tha tosion bars from the 1300 S/axle donor they aren't long enough for the IRS spring plates.

Now i have worked out that i can modify the S/axle spring plates to fit the IRS set up and retain the swing axle torsion bars.

My question is, can any of you see a reason why i shouldn't do this?

You know like ride qualities or some strength issue or something?

Any help appreciated.

Cheers
Ben.

so in short I think your saying your gonna be using swing axle torsion bars in an IRS set-up with modified IRS spring plates.........

from memory I seem to remember the shorter swing axle bars will be stiffer......as the IRS are longer hence they are more softly sprung

if your going for big rear wheels - the long IRS torsion beams will foul the tyres, as chicken found out.......hence the swing axle beams could help you there

but I dont think you could tell the difference if you was to test them back-to back when fitted to a fug........either way I dont think it will cause you a problem using the swing axle bars, as there are many swing axle fugs out there that work fine in fugs.......mine included!

That's good news to hear thanks.

My set up will be swing axle torsion bars and modified swing axle spring plates.
Irs trailing ("A") arms and Irs box, shafts and hubs.

Looking forward to the first test drive :D maybe a few days away though :lol:

Does anyone have any photos to show the difference - I'm still a newbie

Steve

Hi Steve

Welcome!

I'm a complete novice with a spanner too but swing axle only pivots at the joint to the gearbox, IRS axle pivots at gearbox and at wheel.

With suspension decompressed or compressed on a swing axle because the wheel is fixed to the axle at a constant 90 degrees the wheel either leans in or out on the edges of the tyre. With IRS the wheel stays flat to the ground.

In other words swing axle at decompress \-o-/
and full compress /-o-\
IRS |-o-|

Not great drawings and in fact they look like TIE fighters but hopefully you get the idea!

:D Very impressive young paduan, much have you learnt. B) B)

Finally a question I know something about :)

I have used the shorter torsion arm from a swing axle and avoided the clash with the rear wheel. You will either need to cut the spring plate down to length and drill new holes which is a bitch as it is really hard to drill. Or cheat like I did and buy swing plates meant for a bus which will be the right length and have the holes predrilled. The ones I brought have adjustment via a big grub screw to even up the rear without continually pulling the torsion bars out and playing with the splines.

The weld in pivots for IRS needs a jig to position the pivots.
I got an old frame, put a tube on the pivot and welded a bar between that and the torsion bar plate. Unbolt the plate, disconnect the tube from the pivot and you have a jig. The pivot points you can buy for an IRS conversion dont seem to be designed to fit a beetle as the curve in the back of them is the wrong diameter, hack them to shape and trust the jig.

Once you put weight on the rear wheels they will settle in at be at a different angle from where they were when you welded them. Unfortunately I no longer have the jig, I hacked it to bits when I ran short of tube for another project, shame as I need to redo one of the pivots. Not my dodgy welding, just my dodgy reckless driving.

Did the IRS conversion a couple of years ago and its still going strong so more than strong enough for road use.

Picture attached of last weekends abuse :)

I forgot one thing that caused me a little problem. The CVs will foul the frame horns, type 1 CVs are the smallest (98mmdia), Porsche 930 CVs are 108mm dia.

You will need to modify the frame horns to clear the cvs, heat them up and bash the top of the frame horn in with a large hammer. i was lucky as I have steel angle welded to the bottom of the horns to mount the skid pan on so it was already reinforced.

now if I had a quid for every time I have seen this discussed I'd be a rich man :P - if you want the ultimate handling fug - dont be fooled into thinking you MUST have IRS.......as a good comparison - formula vee racers run swing axle set-ups and are on the same pace as formula fords......

a swing axle fug will handle very well on the streets too - as I can confidently say!.........in a beetle with the weight high up - the high centre of gravity really combines badly with swing axle suspension geometry, causing bad camber movement........

but with the minimal weight of a fug - and the very low centre of gravity - when you corner hard - there is literally zero body roll - therefore hardly any wheel travel and camber change - therefore swing axle can handle quite fine........

another point to consider when converting from swing axle to IRS is it will ADD about 10 to 15KG to the rear of your fug due to heavier axles and the addition of the trailing arms and brackets - which to be honest - is just where you dont want it!.......I have a swing axle and alfa-sud combination and its already too tail happy in the wet!......hope that helps

:D B) I LIKE IT :D

Its possible to do. Shorter torsion bars means stiffer suspension. 1302/1303 were susposed to be a 'more refined ' bug and by making the bars longer they achieved this ...sort of <_<

My opinion for wot its worth is providing you are not going too big on the rear tyre size then swap the whole lot. Its not a straight forward bolt on so there is a certain amount of work you need to do anyhow...
But it really depends on wot you want from your Fug. If you are lowering it for street /strip / traffic light grand prix then either swing axle or IRS is fine. Only with a high roll centre does swing axle prove a problem as the inside wheel will try to tuck under as the body leans in a bend. The other thing is once you hit the limit IRS is much much more predicable because as least you will still have all four tyres on the tarmac....we hope :P

If it is for off /on road then I would IRS it with lengthened arms as loads of positive camber on the swing axle makes for a handful :blink:

Yep what he said :rolleyes: :) i'll post some pics of both types in a bit :)

Here you go
This is a standard bug IRS set up

This is a standard bug swing axle set up

And this is half way between,notice the bracket that has yet to be welded in to take the pivot of the trailing arm (sat on the tyre)

;)

Great photos, I'm learning fast. ;)

this is my fug. tackwelded the irs rearaxle in it.

think it's the same as bin jammin is doing

Bit of progress last night with one of our IRS conversions
Some grinder action

Then a bit of welding

and hey presto

There she is then

It's as simple as that! :P :D ;)

When you say last night you mean this morning! :P

I got home at 4am and have had 3hrs sleep.... :blink: :wacko: :blink: :lol:

Yeah sorry :blink: was this morning wasn't it :wacko:

check this link for the ultimate guide on IRS conversion

http://www.blindchickenracing.com/How_to/I..._conversion.htm

looks to me that the accuracy of the jig is paramount to doing the job properly

also check out their other "how-too's" and products - interesting site!

http://www.blindchickenracing.com/How_to/Howto.htm

http://www.blindchickenracing.com/Products...nsion_parts.htm

Yep and you wouldn't believe how many times we offered up, checked, offered up again the jig before we were completely happy. :D

You can just see our jig held in place on the 2nd photo and its braced heavily so shouldn't budge. Hopefully the fug won't drive in circles!

Ours isn't a straight IRS swap. We're using the swing axle torsion tube, bars and spring plates so the extended bars don't foul large tyres.

He's right you know

yes the force is deffo strong within him!

:lol:

Hi all, can anyone tell me if IRS spring plates which use the swing axle torsion bars are available 'off the shelf' as I am continuing with the setup which Ben and Kieron were planning.