Chassis snappage prevention?

[Tommo]

Seen as my polo should have some proper power soon, I was wondering if anyone could provide me with a bit more info on the 'chassis leg snappage' that seems to occur on high powered polo's?

Im guessing this is like what happens to minis where if you rag them enough the front end starts to tear its self away.

I have heard that a subframe can prevent this, but dont they just brace the ARB mounts to the TCA mouts? Im guessing the cracks appear where the legs meet the bulkhead?

Any help is appreciated as always.

Someone on CP managed to sneak a picture of my car, I will stick it up here to show you guys seen as I suppose you havent really seen it...

[hayesey]

I've done the following on mine:

- stitch welded the chassis leg to inner wing joints
- seam welded the joins on the top gearbox mount (the parts that are spot welded together on the chassis leg)
- welded a 1" box section brace between the passenger side chassis leg and the angled part on the bottom of the bulkhead

But the main thing is a subframe, this makes a world of difference because it just stops the chassis legs from being able to move about which they can do quite a lot of normally!  It braces between the inner TCA mounts (which are fixed to the car body behind the chassis legs) and the fronts of the chassis legs.  Plus creates a rigid box underneath to keep the legs from moving from side to side as well.

Short of cutting the whole lot off and making a space frame I reckon that's reasonably good.

[hayesey]

oh one other thing I've done is add an extra gearbox mount at the front using part of a mk1 golf small block mount.  It mounts to the box section brace I made which also holds my intercooler and radiator.  You can see the brace I mean in this photo when I was mounting my intercooler, don't really have a pic showing the mount itself but can take one if you want me to:



I like to think this mount spreads some of the rotational load from the engine so there's less on the top gearbox mount.  Although it's basically still absorbed into the chassis leg hopefully some of it transfers to the subframe from here.

[jez1272gt]

The pic below shows the main things to weld in the engine bay. The braces are at the base of the chasis legs as Haysey has mentioned. The suspension turrets are worth stitching whilst the welder is out along with the gearbox mount and the chasis legs to the wings. Basically any seams in the engine bay area are worth stitching if you want to go all out. The main ones are the leg bracing, gearbox and turrets though. The less flex the better (to an extent)!

[lance]

nice work there jez your polo is gonna be summat special!

[Tommo]

Yeah cheers for that its most helpful.

Has anyone braced the cylinder head to somewhere to take some of the load off the engine mounts? The bulkhead seems very weak for this, I was wondering about somthing that came from the strut towers. More stuff to look into!

[breadman]

Tommo, the idea of bracing the engine at the head is a good one. However, this is normally done using a bar that runs fore and aft to reduce engine movement under acceleration and decelleration. It's a mod commonly carried out on Minis.
Fitting a bar that runs laterally from the head to suspension turret wouldn't do much good as sideways movement is only minimal.

[PeteG40]

some people - hayesey - run an extra front engine mount as used on 1.3 golfs

[Tommo]

Tommo, the idea of bracing the engine at the head is a good one. However, this is normally done using a bar that runs fore and aft to reduce engine movement under acceleration and decelleration. It's a mod commonly carried out on Minis.
Fitting a bar that runs laterally from the head to suspension turret wouldn't do much good as sideways movement is only minimal.

Minis have the head brace as standard. I was thinking more a type of strut brace across the turrets (maybe triangulated to the bulkhead?) with a bracket on it for the head, rather than just a bar from the head to a turret lol. It sounds pretty gash at the moment but its all still ideas.

[Nick_S]

some people - hayesey - run an extra front engine mount as used on 1.3 golfs

Hayesey's came off a Scirocco i broke for spares.

[hayesey]

yeah my front engine mount is made from a mk1 golf/scirocco front mount which I cut up and welded bar onto to make it fit. 

I've never seen anyone brace the head on a polo, it's not a bad idea but I think what I've done already does the job for me.  Plus as you have said, there's not much strong enough to brace to around there.