Broken R200 moustache bar with RB conversion

[dat240z]

Hi guys, just to see you opinion. Ive put almost 350km on the 240z after my build without any real issues. Suprising considering the whole mechanincals of the cars have been altered now.

 

When driving the other day i noticed after giving it a little, during a shift i could here a bang from the rear end. Every time i jumped on the accelerator and especially when hitting boost, when changing gears i kept getting this sound. Sort of when its tranfering load i guess.

 

Upon inspetcion i couldnt find anything out of place of obviously wrong. I lifted the car onto stands and drove through the gears with a mate at the arse seeing where the noise was coming from.  He noticed during the shift, just after getting off the accelerator the moustache bar had a split in it and would flex considerablly leaving a 3-5 cms gash/split in the bar, resulting in the diff to move and bang....

 

I think it must have been a hairline crack when purchased and its just given way, especially with double the original HP now.

 

Have you experienced similar issues at all with weakened r200s? is there a chance it will re-occur, or should i brace /support it?

 

I noticed AZC has a nice billet moustache bar for $250... looks solid too

 

[C.A.R.]

Yes, it can happen.

 

All I'd do is just cut & grind the crack out with a nice 'V' prep & weld it up again

[PeterAllen]

I’m no metallurgist but I thought the moustache bar was a heat treated spring steel material and hence that’s why it has cracked rather than distorted. If that’s the case, welding may; (a) not have the desired fusion and, (b) destroy the heat treated properties. I would fit a replacement.

[dat240z]

Yeah i replaced with another r200 bar instead of the weld solution..

 

 

[MaygZ]

I wouldn't be quick to dismiss Lurches advice - he is a welder/boiler maker.

 

However, and I suspect you're mind is already well down this path, I would buy the AZC bar!  Much shiney.  Much bling!

 

MaygZ

[RB30X]

From my experience in welding up cracked heat treated steel (some, but not very much), a second crack will develop on the edge of the weld where the strength has been lost from the heat of the weld. I'm sure there are ways to get around this such as heating the steel up with an oxy, then welding it then quenching it or something.

 

Since you've swapped to another one anyway, why dont you experiment with the cracked one by welding some angle or RHS or Box section to the bar to give it some added torsional strength, hopefully more than the spring steel added initially.

 

If you're just going to chuck it out, send it to me and I'll do it. My torque is distributed more evenly through the revs rather than a big slap in the face like yours would.

[C.A.R.]

I'm starting to understand where Peter Mac is coming from...

 

There is no reason the replacment m/bar should crack - I dare say your old one would have been damaged in some other way.

[RB30X]

So your saying the original items are fine and there is no need what so ever for the billet items that all those companies make?

 

We're not talking about standard L series engines here Lurch

[Ledge]

Hi

I have a rb26 with over 330 at the wheels on semi slicks and the trottle is almost always wide

open and i have not broken the standard bar.

When i do AZC all the way

 

 

Regards

Paul

[C.A.R.]

So your saying the original items are fine and there is no need what so ever for the billet items that all those companies make?

 

We're not talking about standard L series engines here Lurch

 

Yes I am.

Craig (620Z) has 580hp at the wheels & has not broken his!

 

Feel free to prove me wrong Tim...

 

[RB30X]

I'll let you know Lurch. Hopefully heading to the drags this weekend.

 

I noticed Peter Mac has upgraded his?

[dat2kman]

Hmmm, lets see, i have a piece of steel, of a certain molecular structure, and it has holes in it to mount things.

These are stress riser points.

I flex this bit of steel, a lot, for 30 or so years.

The molecular structure is strained it cracks.

 

Bound to happen one day, no brainer.

 

Welding a crack, with suitable holes at each end, to prevent crack spreading, is common. If it is a higher tensile steel, and this item has to be, due to its design use, it will have been heat treated, to ease any potential deformation of structure, then send it away for re heat treatment, after welding.

 

Or just bung in another 30 year old one and cross fingers.

Yes, i concur, Pete Mc is on the ball

 

Some of us on here may know a thing or two, but, as we all know, everything published on the intetwebs, by everyone, is 100% gospel truth and will work.

[C.A.R.]

I give up.

My opinion is incorrect.

 

Goodnight.

[RB30X]

Yes I am.

Craig (620Z) has 580hp at the wheels & has not broken his!

 

Feel free to prove me wrong Tim...

 

Well I have decided to go back to the original Moustache Bar. Whilst I had broken one before I think it was pre the front diff brace I have in place now. The orginal design does allow for a lot of movement and should resist cracking and fatigue so I will put the old one back in and see how we go.

 

Here

 

http://www.viczcar.com/forum/index.php/topic,5913.msg51446.html#msg51446

 

 

 

[dat240z]

Wow, this has heated up since lsat visit!!

 

I think Lurches solution is definatley a good idea, and i also agree it propably already had a hariline crack or some weakness before fitted.  Extra power has exposed problem.  I like the arizona billet moustache bar 50%looks/50% function and wonder if that will bolt right up to a r200 backend?

[NZeder]

my question would be this (and I would also do as Lurch pointed out)

 

Does your car run a solid front diff mount?

[dat240z]

Yeah, i originally used the strap (massive stretch) to get over the new r200 but it just felt weak.  So I got a solid diff mount from SW Motorsports.  He reckons hes never broken one on a rally or drag car.  Seems good so far.  Ive installed aother r200 moustache bar and its been fine since so we will wait and see for the future. 

[NZeder]

my guess is that is why your moustache bar fractured due the solid lower diff mount - something got to give.

 

I would go for a stiffer than stock lower diff mount - then a RT diff top mount - but put a bump stop on it and have it set to just touch/compress when the lower mount is done up. This way there is still some movement so not all the load is transferred to the moustache bar. Or I have seen a chain in rubber hose replacing the top strap work very well.

[Whittie]

I broke one down at the drags, ONLY and L28, but that was because I ripped the front diff mount and that allowed the diff to move around a LOT, stressing the moustache bar and causing it to crack right where the diff mounts, at the holes. Welding is always an option, but a new bar only costs a pittance and is cheaper than paying labor rates, unless you can do it yourself, so that is what I did and would suggest.

 

I replaced with a new, decent, solid, front mount that won't tear, put in another 30yr old replacement at the back and have had happy days since.

 

As you came to, probably strained/stressed previously and gave way under a hard gear change.

[dat240z]

agreed Whittie.  I remember also when test driving before upgrading to the solid SW diff mount that the strap loosened causing the diff to raise and bang on the underside of the car.  That i guess would have caused considerable flex on the bar too, so after the diff mount upgrade that became the weakest point and gave way.