NTS MX5 Build

[wylliezx9r]

Originally Posted by MarkB

Never made a car in my life or so much as looked at a tub of resin so quite why I comment on things is beyond me.


Think triangles and all will become clear

I don't think anybody is doubting your knowledge or technical ability its your ATITUDE . You have helped me in the past and for this I'm greatful but why do you seem to be constantly digging at people with cryptic comments that don't help anybody ?

[Bonzo]

Originally Posted by MarkB

Never made a car in my life or so much as looked at a tub of resin so quite why I comment on things is beyond me.


Think triangles and all will become clear

There it is in a nutshell mate !!

You honestly believe that you are the only one who has ever opened a tin of resin or allegedly built a kit car.
Again, I think you honestly believe that you are the only one who knows how to grow Onions ( As you put it )

Sorry to be the bearer of bad news, some of the local boat builders down here also know their Onions, that's how they manage to stay in business.
If I were feeling in a spitefull mood, I might say that they could make your work look like apprentice pieces but I won't
Same can be said of some of the kit car manufacturers, again, they manage to stay in business just fine.

Lot more technicaly minded folk out there, a good few on this forum

Get over yourself mate & move on with whatever floats your particular boat.

[trick-kit]

Now here's a theory, given that this problem isn't solely confined to Locosts but exsists in MX5's too, maybe it's not the mounting of the diff that causes the problem (OK, if it's allowed to move around too easily then it may highlight the weakness) but MX5's that have broken the diff have pretty much the same thing in common.

They have been involved in an accident.

The diff has a cast sacrificial point in it designed to break to prevent the PFF puncturing the tank. Now given that most of the kit cars using the MX5 as a donor are built from wrecked MX5's maybe we are inheriting the fault without noticing it.

As i said, just a theory

TK

[CTWV50]

Your correct it does appear they've made a point at which they want it too fail so actually what we need to do assuming we don't have a crash damaged diff is to protect the diff from violent movement which makes sense.

[Big Vern]

Originally Posted by trick-kit

Now here's a theory, given that this problem isn't solely confined to Locosts but exsists in MX5's too, maybe it's not the mounting of the diff that causes the problem (OK, if it's allowed to move around too easily then it may highlight the weakness) but MX5's that have broken the diff have pretty much the same thing in common.

They have been involved in an accident.

The diff has a cast sacrificial point in it designed to break to prevent the PFF puncturing the tank. Now given that most of the kit cars using the MX5 as a donor are built from wrecked MX5's maybe we are inheriting the fault without noticing it.

As i said, just a theory

TK

It is true some of the donors used may have been involved in accidents but by no means all of those being used have been in accidents - many are now cheap enough (mot failures etc) to be used as donors without any accident history.
Not aware of MX5's suffering diff carrier failures. Anything likely to compromise the diff will like as not cause it to fail though there's always the 'exception that proves the rule'
Usually in a front or rear impact the power plant frame bends downward twisting the nose of the diff down to the road to avoid pushing through and puncturing the tank, this action usually fails the diff carrier so few would have made it on to other cars for further use or be available for sale as salvage.
The diff failure, as happened to Nathan, is something I've seen before and on diff carriers that were known not to be compromised, though I get the point we should all be vigilant and inspect all used parts in the build for signs of damage/fatigue.

[trick-kit]

http://www.mx5oc.co.uk/forum/forums/t/34429.aspx

This thread lists a few examples and shows the diff in the MX5 subframe.

TK

[Big Vern]

Originally Posted by trick-kit

http://www.mx5oc.co.uk/forum/forums/t/34429.aspx

This thread lists a few examples and shows the diff in the MX5 subframe.

TK

This is accident damage or the result of, and cracked diff that may have been missed by the repair shop if they wern't looking for it. I accept there might be the odd rogue part that has cracked but not completely failed at the time of the acceident and that could get onto another car as a salvage part - as I said we should all be vigilant in checking the condition of our used parts.

Not aware of any in service failures of cars that have not been in some sort of accident so I don't believe this is an inherant failure of the MX5 dif when used in an MX5.
As I've said elsewhere in this post its only designed to resist rotational forces about the propshaft axis. When used in isolation and without proper constraint the diff can and will rotate about the driveshaft axis or indeed any fore aft movement as you have pointed out will cause the diff to fail as it did on Nathan.
As I have previously stated Nathan would do well to implement a better way of contraining the the diff movement as the method he has used hasn't worked. I can fully understand why he did what he did and he's not the first to have tried something like that nor is he the first to have had such a diff failutre.
As I have said all along the key to this is understanding the forces involved and engineering a solution to constrain them. Some good suggestions as to how that could be done have already been presented.
Did the diff Nathan originally use come from an accident damaged car? I thought not if it was the one Saturn started out with.

[skov]

Originally Posted by Big Vern

As I have previously stated Nathan would do well to implement a better way of contraining the the diff movement as the method he has used hasn't worked.

This particular failure was due to Nathan forgetting to fit the two big washers that restrict the rotational movement of the diff.

It still remains to be seen whether the design as intended works or not.

[trick-kit]

Originally Posted by Big Vern

This is accident damage or the result of, and cracked diff that may have been missed by the repair shop if they wern't looking for it. I accept there might be the odd rogue part that has cracked but not completely failed at the time of the acceident and that could get onto another car as a salvage part - as I said we should all be vigilant in checking the condition of our used parts.

Agreed, and i did state this fact in my post, the point i'm trying to make is that people are assuming that the failures of the diff when used in LSIS kits is because of poor location when it would seem that as it does not affect every kit made but just a small percentage, rather than the builder just being lucky there is some other reason.

It would be interesting to find out from those who have suffered diff failure in an MX5 LSIS how many of them used cars that were insurance write offs. I bet there would be a high percentage.

TK

[Big Vern]

Originally Posted by trick-kit

Agreed, and i did state this fact in my post, the point i'm trying to make is that people are assuming that the failures of the diff when used in LSIS kits is because of poor location when it would seem that as it does not affect every kit made but just a small percentage, rather than the builder just being lucky there is some other reason.

TK

Not every kit has poor location of the MX5 diff, a study would need to be carried out to determine who's kit did or did not break the diff. From what I have seen all those experiencing trouble do not have the diff properly constrained! a point I have been making through out this thread.
Failures of the MX5/RX7 diff when used in isolation are due to poor mounting design with insuffiecient constraint of movement. This is a known problem and there are plenty who have come across this problem - just google search and you will find.
Poor location will cause diff failure as I have tried to explain, Nathan failed to fit the diff washes and that contributed to unconstrained diff movement. A compromised diff could also cause failure but I am aware of people building westfield miata's amongst others including the MNR who are also having failures where the diff has not come from an accident damaged car.
Whilst I get the point you are making RE: the need to be vigilant in checking the parts we use for building cars don't assume that the failure was neccessarily because it must have previously been in an accident and blindly go on believeing the inadequate mount arangement will be alright. Nathan forgetting the washers for the rear isolaters may well have played a part in this.

BV