MOT passed - just

[robp]

I've been really busy at work over the last few months and also moved house a few weeks ago so the Westfield had slipped down my list of priorities.  It ended up with the MOT expiring and also going on SORN.

Anyway, with the Spring coming and the clocks changing I thought I'd better get things sorted out.  I booked in for an MOT test.  Since the car has been layed up for a while I thought I'd better give it a quick once over.  All the lights were working, all the front suspension/brakes seemed in order.  However, when I got under the back, there was something hanging down.  The rear anti-roll bar was broken!  Not sure when it went but I sure wasn't during the time in the garage!! 

Fortunately, I just had to remove it for the test.  I'll weld it up and re-fit it when I have some time in the next few days.



The car passed the test!

Right, so that's the MOT done.  I'm not going to bother getting road tax until next month.

[robp]

.... so the Westfield had slipped down my list of priorities.

Not to mention the poor old Spit. 

It's been sitting outside on a trailer since the move.  Garage at the new house is nearly sorted so, hopefully, work will commence again soon. 

[Moleman]

Glad it passed mate. 
My anti-roll bar broke on that same place a few years back, I think that must be a weak point on them? 

[Bulldog Bri]

Phew. That was lucky. Though I bet the ride had got a bit softer.

[Lucky Ed]

Nice one Rob, it's good to know I'm not the only person to break stuff

['The Gaffer']

Hope you get your garage sorted soon, looking forward to the updates again

[Iancider]

Rob,
Looking at yours you can see why it broke because the rod is hollow tube at the point of greatest stress.  I would seem better that the shaft was solid through the bearing blocks but remaining tubular in the centre section acting as the torsion bar. This should transfer all of the load to the centre tube where is meant to rotationally twist. At the lever arm I can imagine there would be lateral force as well, inducing fatigue.  I guess you will need medium carbon steel to make the rod.  I have also wondered how wise it is to have steel running in an Aluminium bearer - I feel that a hard Nylon6 sleeve would be far better in there - otherwise Steel will wear Ali very badly - I think mine is already rattling.  I might be wise to have a word with Westfield to learn their latest view on this. 

Finally, I have wondered if an ARB is required at all.  They definitely make the ride quite hard but on such a low car do they add much?  When I have time, I am going to decouple front and rear to see how it behaves without - I suspect it may behave better on the highway and I have built my car for touring rather than racing and it migh remove my rattles.

Good luck
Ian

[Moleman]

I would wait until after abingdon Ian. 

[Lucky Ed]

As Colin says you might change your mind after a track day.

If you're sure you don't need your ARB's you could always chuck them my way

[robp]

Rob,
Looking at yours you can see why it broke because the rod is hollow tube at the point of greatest stress.  I would seem better that the shaft was solid through the bearing blocks but remaining tubular in the centre section acting as the torsion bar. This should transfer all of the load to the centre tube where is meant to rotationally twist. At the lever arm I can imagine there would be lateral force as well, inducing fatigue.  I guess you will need medium carbon steel to make the rod.  I have also wondered how wise it is to have steel running in an Aluminium bearer - I feel that a hard Nylon6 sleeve would be far better in there - otherwise Steel will wear Ali very badly - I think mine is already rattling.  I might be wise to have a word with Westfield to learn their latest view on this. 

Yes, I'm not sure they are the greatest design.  Should be easy enough to repair though.

I have wondered if an ARB is required at all.

Leave them on until after Abingdon. 

[TimC]

Light cars with significant power/pace will still benefit from ARBs, in particular on-track.

Our own Camber Dave made mine - having done all the necessary measuring:

[benchmark51]

I recognise his left foot. 

[Iancider]

Thanks for the advice Tim,

Yours looks pretty sturdy.  I note you mounting blocks - they look like plastic composite - is that right?  I am wodering if that is what I need to get rid of the disturbing clonk.

Ian

[Moleman]

I was going to change mine to nylon mounting blocks over the winter but got side tracked with changing the engine. 

I did manage to paint on a anti-slip coating on to my blocks which I got from work which seems to work really well. 

[Moleman]

Well Rob Snap! Quite literally. 



Looks like Abingdon killed this one off. I checked to see if it was running freely on the alloy clamp blocks & it was moving smoothly so it just must be a weak design fault & I think the tube should be a solid bar instead. 

[Iancider]

Looks like the same failure point Colin,  This is clearly metal fatigue at the stress point right next to the mounting block.  It indicates that if it is repaired it will just go again.  The design looks wrong to me because they look too rigid and all of the stress will concentrate next to the mounting block.  I have looked a web commentary on suitable alternatives and the simple unwelded bar from Plays Kool looks better - there will not be a clear stress point in that. 

http://www.plays-kool.co.uk/acatalog/Anti_Rollbars.html

Or if you can afford the racing version form Siltech:

http://www.libell.nu/Siltech.html

I am just waiting for mine to break it clonks loudly now - it just seems too rigid.

Regards
Ian

[Moleman]

Thanks Ian. I have contacted Siltech Racing & they really seem to know there stuff & they are very helpful. It's a small company that manufacturer all their own bits.
They did explain how the westfield bits are too stiff which won't allow any give causing them to break.
He has told me as theirs are one piece built to top grade standards which are stronger, lighter & give a bit so these will not break.
He has even given a guarantee that if it breaks he will replace it for free.  (unless you stuff it in a wall obviously).
I will keep you posted & start a new tread when I have it. 

[Iancider]

I will watch carefully cos I think mine will go the same way.

[TimC]

Sorry chaps - I'd missed this post.  Dave machined the mounting blocks, I think, from Delrin.

I'm actually thinking about getting the bars themselves non-stick coated (Teflon-alike) - a bit unnecessary maybe but I have a contact.

[Camber Dave]

I saw this thread back in April but missed Tim's post. Thanks Tim.

I have modified at least half a dozen Westfields and analysed dozens of others for spring rating.

I recommend using Westfields' or Playschool etc own front ARB as they are about half the price of my made ones. (see Tims photo's). However the bars supplied by Westfield are too stiff by my calcs. Although adjustable, the range remains as a rear bias to the weight transfer. This is difficult to explain in a post but anyone more interested is welcome to come a look over the data.

The ones I make are either 12 or 16mm solid with tight bends to make sure the torsion bar works at the calculated length give a wide range of adjustment to the adjusters on the lever.

As spec'd my bars will be neutral but give understeer (long adjustment) to power oversteer at a hard (short lever) setting.

I have been reluctant to push this service on a forum but I recently made a new rear ARB to balance the stiffer front springs on my MX 5 and the car behaves just like the programme predicts. The Yaw trace on the data logger also confirms driving impressions.

Dave

[TimC]

The Yaw trace on the data logger also confirms driving impressions.

Dave

That's bloody flash!

[benchmark51]

The Yaw trace on the data logger also confirms driving impressions.

Dave

That's bloody flash!

Is it, I'm still trying to figure it out.

[Camber Dave]

I'm still learning, no teaching, myself. I am constantly amazed at what is shown.

The logger records Vertical (Z), Longitudinal (Y) and Transverse (X) Accelerations with a GPS speed trace.
Internally it calculates a Yaw trace displayed in Deg/Sec.

On the screen the transverse trace records cornering G and the Yaw shows an opposite displacement. Yaw is larger when understeering such as low speed 'U' turn. 
When the car oversteers the trace goes with the X trace. If the tail slides it shows a spike. 

What I am seeing since the new ARB is the Yaw trace remaining closer to zero despite high cornering force. ie low speed of vehicle rotation about its C of G.

[Pilgrim Anna]

Well done for getting it passed!

[paintman]

What language is Dave talking in please......I got lost after the word "The" ? ? ?

[Moleman]

Sorry Dave me too.      But I will leave this to be done to my car by your expert hands. 

[benchmark51]

I think that it is to do with the angle of the dangle.