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skov

22nd July 2013, 01:20 PM

https://lh3.googleusercontent.com/-fK_JMDxTPUo/Ue0jKGdxcYI/AAAAAAAAJtc/m75DxdUINAU/s1152/2013-07-22%252009.09.00.jpg

Back to the drawing board then... :rolleyes:

Stot

22nd July 2013, 01:37 PM

Ouch, JB Weld?

Did this happen when you gave it some or just general?

Cheers
Stot

skov

22nd July 2013, 01:43 PM

I was thinking a spot of Araldite should do it.

I believe it happened whilst I was testing how fast the rev counter can reach 7000 rpm from a standing start.

Stot

22nd July 2013, 01:56 PM

I believe it happened whilst I was testing how fast the rev counter can reach 7000 rpm from a standing start.

Just a Sunday drive then..

On the bright side, at least you didnt spend hours reconditioning and painting your diff! (Thats going to be my excuse for not doing it. :o )

Cheers
Stot

skov

22nd July 2013, 02:09 PM

Just a Sunday drive then..

On the bright side, at least you didnt spend hours reconditioning and painting your diff! (Thats going to be my excuse for not doing it. :o )

Cheers
Stot

Yep, my laziness did pay off for once :D
I figured no one's ever going to see the diff so there wasn't much point. Saying that, the RAC man did have a good look!

vmax1974

22nd July 2013, 02:10 PM

damn and yours was the best idea i had seen to sort the ppf issue could be a tough one to get round

skov

22nd July 2013, 02:17 PM

I think my mistake was using the land rover mounts in shear.
should have known better really :o

james3004

22nd July 2013, 03:13 PM

Not so good :(

skov

22nd July 2013, 03:26 PM

Not so good :(

Not ideal, but you've got to expect a few teething troubles!
Looks like I might not be able to take you for that spin I promised you for a little while James :rolleyes:

jason 82

22nd July 2013, 04:24 PM

Really gutted for you. Maybe it's worth buying Phils sierra style rear diff plate. About £150 I think he said. Trouble is, if you buy it, you have to completely re fabricate the rear cage. :eek:

jason 82

22nd July 2013, 04:35 PM

Quick thought, the only difference between how the diff is mounted in an mx5 & your roadster, is the brace that goes from the diff forward. I know this is too bulky, but, if you used a bar with female ball joints on each side, this should stop the problem. I think that the diff is twisting under strain, snapping the arms, hopefully the female ball joints should allow enough movement to take the load off the diff when you are pushing on. :rolleyes:

CTWV50

22nd July 2013, 04:53 PM

I was thinking a spot of Araldite should do it.

I believe it happened whilst I was testing how fast the rev counter can reach 7000 rpm from a standing start.

Ahahahahaha!!! Whoops! :D

CTWV50

22nd July 2013, 05:06 PM

https://lh3.googleusercontent.com/-fK_JMDxTPUo/Ue0jKGdxcYI/AAAAAAAAJtc/m75DxdUINAU/s1152/2013-07-22%252009.09.00.jpg

Back to the drawing board then... :rolleyes:

I think we all have this to look forward too, guess the mx5 diff just ain't made to be not solidly mounted! Might keep hold of that 1.8 diff as a spare for when mine goes.

Spikehaus

22nd July 2013, 05:14 PM

Opps, that must be really frustrating when its pretty much your first ride. Still whatever happens, it can't be as bad as it was going through the IVA. Sure you will have it fixed in no time.

PorkChop

22nd July 2013, 06:20 PM

First up, glad to hear it sounds like you're OK Skov, that could really hurt if bits of metal get loose!

Second of all, the issue of mounting the MX-5 diff has been discussed, at extreme length, in the past when Nathan suffered a diff failure during testing. Now, the reason for his failure was different - it wasn't bolted in correctly. But the discussion that followed concerned the diff nose mounting specifically. Keith Tanner's build used a box section frame, with captive nuts, and a part of it was welded to the transmission tunnel. In other words, the nose was solidly mounted. After a couple of years, he removed it during a diff change IIRC and found no issues with it whatsoever.

Every kit car manufacturer that uses the MX-5 diff has solidly mounted it AFAIK, including the diff ears (or in the case of GBS, cut them off altogether and bolted the top part of the diff to the chassis).

Now, I'm not a trained engineer, but it appears you need to replicate the PPF. The PPF is solidly mounted to the diff and the gearbox tail. There are no compressible mountings between the two. This fits in with what the kit car manufacturers have done.

So do I think that a broken diff arm (Mazda deliberately engineered a failure mode in the arm) is an inevitability? No. On my newly acquired build, I have a set-up identical to Johno's design, where there are 2 rubber Land Rover V8 engine mounts, fitted so that 1 mount would always be in compression. I'm planning on substituting these mounts for 1 piece solid versions in a material such as ali or nylon. The diff ears will either be polyurethane or solid again.

skov

22nd July 2013, 08:11 PM

Only my pride that's been hurt so no real damage done :o
Luckily I'd only just pulled away from a junction at the time, so wasn't going very fast.
I do recall all the discussion following Nathan's diff fail, but I think I'd already mounted my diff by then. I've always had it in the back of my mind that it'd probably fail at somepoint, but thought I may as see how long it lasted... I'm a bit of a lazy git like that!
I think what happened is that the landrover mounts failed and at that point the diff could move enough to rip itself apart. I suspect if I'd done it properly with them in compression it would have been fine.
Saying that I am going to solid mount the next one.

jason 82

22nd July 2013, 08:15 PM

http://www.mpsgarage.com.au/shop/product/521/generation-1---90-97-engine--mazdaspeed-motor-mounts.html

Mx5 boys check out the diff mounts here on the above link. They are proper diff mounts for the mx5 arms to stop the snapping of the arms. :cool: they are proper Mazda speed items.

PorkChop

22nd July 2013, 08:30 PM

jason 82

23rd July 2013, 05:14 AM

Sorry about that. I found them on a forum that the drift boys were using, as one bloke was complaining of the same problem, and that was what somebody suggested. Do you think Phils idea will work ? I want to see somebody try it before me, I hate being a guinea pig. :D

Enoch

23rd July 2013, 08:52 AM

Blinkin eck, that's something you don't want happenning too often. When I first started building my new monster I was very concerned about mounting the diff. The forces involved in an IRS set up are very complex. The assembly has to be able to handle the torque from the engine, the torque driving the wheels and the lateral forces involved in accelaration and retardation. It basically seems like every part experiences forces in every direction under one condition or another. Any weakness in any direction can result in failure. There is a web site in the US of A dedicated to irs setups its this one here: http://irsforum.boardhost.com/viewforum.php?id=1 There may be some useful info buried within that will help get to the bottom of this.
Best of luck.
Dave.

Johno

23rd July 2013, 02:03 PM

Bugger:(
Glad to see you're ok, did it cause any damage else where?
I'm guessing solid mounting is the way to go now by the look of it.
Which way is the diff trying to rotate looking at it from the rear out of curiosity when going forward.
Well hope you get it back on the road soon.

Davidbolam

23rd July 2013, 02:45 PM

Nightmare mate!

Have a look at my flickr page. There should be a photo of how I have solid mounted the nose of my diff with a very big bolt. On my jollies so can provide the full link. Will post some photos when I get home

David

Stot

23rd July 2013, 03:20 PM

When the wheels are being driven forward the nose of the diff will want to pull up.

This was what I have plumped for along with some solid aluminium 'bushes' in the diff ears instead of rubbers it should keep it in place and any upward force should be directed into the cross members.

https://lh4.googleusercontent.com/-4sr_YlMBJHQ/UaJgHSZe6CI/AAAAAAAAFCw/8vcCE58CNFw/w800/newaxis2.JPG

I may buy a spare diff now though... :o

Cheers
Stot

CTWV50

23rd July 2013, 03:38 PM

I think it would be advisable to use copper/nickle 90/10% brake and fuel pipes with a solid mounted diff, plain copper may fatigue easily with vibration so I have read.

jason 82

24th July 2013, 05:06 AM

Quick thought, would an LSD be immune from the broken mounting arms ? I say this because with an LSD you get little or no spin at the drive wheels, meaning hell of a lot less vibration on the rear end & diff. :confused:

beardydave

24th July 2013, 06:04 AM

I think an lsd would be worse, when that lets go there will be that much more power going through it.

skov

24th July 2013, 01:50 PM

Looks like my propshaft is buggered too...
The UJ at the diff end can slide from side to side by half an inch or so :(

jason 82

24th July 2013, 01:57 PM

Really gutted for you. Have you come up with a battle plan yet ?

skov

24th July 2013, 02:13 PM

Really gutted for you. Have you come up with a battle plan yet ?

Cheers mate. I wasn't too upset until I found the propshaft was knackered too... really don't want to be spending a load of cash on a new one at the moment :rolleyes:

Current plan is:
1. Get another diff and replace the rubber mounts in the arms with solid ones.
2. Make up some solid spacers to replace the landrover mounts
3. Get a new propshaft
4. Bolt it all back together and see how long it lasts.

If it seems alright I'll make a new nose mount at some point to get rid of the fake landrover mounts.

CTWV50

24th July 2013, 11:54 PM

Looks like my propshaft is buggered too...
The UJ at the diff end can slide from side to side by half an inch or so :(

Oh, that's not so funny, bugger! :(

Stot

25th July 2013, 06:47 AM

really don't want to be spending a load of cash on a new one at the moment :rolleyes:

If its just the UJ thats gone Dunning Fairbanks can replace them even though they are staked, they have done quite a few MX5 props for kit cars.

They quoted me £85 + VAT to shorten, balance and replace both UJs. I didnt need UJs in the end so it was only £45 + VAT to shorten and balance which by my reckoning is £20+VAT per UJ.

Cheers
Stot

skov

25th July 2013, 09:27 AM

If its just the UJ thats gone Dunning Fairbanks can replace them even though they are staked, they have done quite a few MX5 props for kit cars.

They quoted me £85 + VAT to shorten, balance and replace both UJs. I didnt need UJs in the end so it was only £45 + VAT to shorten and balance which by my reckoning is £20+VAT per UJ.

Cheers
Stot

That sounds like a bargain! I think I emailed them yesterday, along with a load of other propshaft specialists, but haven't heard anything back yet.

Incidentally, when I was googling MX5 propshaft repairs forum posts kept popping up from Westfield SDV owners with failed rear UJ's...

skov

25th July 2013, 02:20 PM

Here's the response from D&F:

Price to replace your UJ will be £55.00 + vat
A new shaft will be £160.00 + vat, made to length.

james3004

25th July 2013, 03:17 PM

Looks like I might not be able to take you for that spin I promised you for a little while James :rolleyes:

Hurry up I want my ride! :D lol

Seriously tho hope it don't cost you too much to fix it!

I'll be consulting your knowledge soon mate as I progress onto different parts of the build

skov

25th July 2013, 03:42 PM

Hurry up I want my ride! :D lol

Seriously tho hope it don't cost you too much to fix it!

I'll be consulting your knowledge soon mate as I progress onto different parts of the build

Just don't consult me on how to mount your diff :D

james3004

25th July 2013, 07:10 PM

My diff is the least of my problems at the moment! lol

I'll be amazed if I can ever get it to move under its own steam!

Davidbolam

25th July 2013, 09:15 PM

I got drivelink in team valley close to me to shorten mine. It was 35 plus vat.

If you phone ak automotive 01207544071 in rowlands gills. Ask for frazer and say you know me " the guy buying all the bits for the kit car" he should have about 20 on the shelf and cheap.
I will pop along collect it drop it off at drivelink and post it to you after I'm back from my hols! As long as you give me the correct length!

David

skov

27th July 2013, 11:32 AM