Lap 8... Jump on the brakes at 100ish mph and BANG
As they say, A picture speaks a thousand words.. So here are 2 pictures.
Anglesey today.
Lap 8... Jump on the brakes at 100ish mph and BANG
As they say, A picture speaks a thousand words.. So here are 2 pictures.
Is the metal on the chassis all clean and shiny, or rusty in places?
Holy shit. Looks like the weld has weakened the tube which looks very thin!
Don't know if it's the photo but that tube doesn't look much thicker than the paint!
Looks like a stress fracture, possibly aided by hydrogen embrittlement of the weld. At the end of the day it's only 16g tube, are you running
slicks ?
Think I would be tempted to replace the whole tube on both sides of the car and braze the brackets on rather than weld.
Hard to tell from the pics, but if it's a flat bracket welded to round tube, then it's a poor design as well, the bracket needs to wrap
round the tube or have some gussets.
Al.
[Edited on 26/5/14 by Wadders]
I wonder how much turning torque or force there is when you slam the brakes on, Probably a ton or more trying to rotate the wishbones before the tyres
brake loose. Couple of tonnes for an instant trying to rip the brackets from the metal.
Any slight pin holes or flaws in the weld area leading to stress fractures and over time that, I would suggest that is what you get. Brown trouser
moment, hope you are OK and no one else taken out.
If all new fracture would be clean all around, if some of the fracture has been there for a while then possible signs or corrosion on parts of the
fracture or at least a discolouration as pointed to by DIY Si.
Adrian
Seized rose joint?
There is certainly some discoloration around the break. It's not clean and fresh by any means..
Is it even 16swg ? looks more like 1.2mm ???
[Edited on 26/5/14 by big_wasa]
What car is it off I would agree that the material looks a little thin for using where excessive force is going to be applied through either braking
or suspension movement. This joint will have been receiving stresses in at leat 2 planes due to braking and the movement of the suspension.
Other with the same car may need to check theirs especially when you state this has discolouration this would indicate a prolonged problem
Gotta ask - is it a home built chassis or from a manufacturer? If it's a manufacturer other owners need to know so they can check theirs
Yupp. Looks like a brittle fracture in the heat affected zone of the parent metal, The tube looks like it could be 18 swg tube which is 1.2 mm
thick thinners than 1.5/1.6 mm thick.
The joint design is less than ideal, forming the bracket as a strap bent around the tube would be better.
I would also go for bronze welding (brazing)that type of joint in that material.
[Edited on 26/5/14 by britishtrident]
[Edited on 28/5/14 by britishtrident]
To me, the chassis tube looks too thin walled for the location and the flat bracket to round tube design looks wrong.
What car/chassis is it?
Looks like an MNR
Is the lock nut loose, it looks it from the picture, although I'm not saying that's the reason for the failure.
The steel looks extremely thin, I often wonder if some manufacturers use inappropriate steel all in the name of weight reduction.
I was advised by a large company that supplies specialist steel too Motorsport teams, not too use T45 unless you have the correct facilities too weld
it, as the welds would make the steel brittle if not done correctly. You shouldn't weld it with just the usual mig set although I can't
remember the exact reasons I was told.
Might be worth a word with the manufacturer and see if the chassis can be strengthened for your future use.
quote:
Originally posted by chris mason
Looks like an MNR
...
I was advised by a large company that supplies specialist steel too Motorsport teams, not too use T45 unless you have the correct facilities too weld it, as the welds would make the steel brittle if not done correctly. You shouldn't weld it with just the usual mig set although I can't remember the exact reasons I was told.
...
That's a long way to go for 8 laps 
The metal looks dirty on the right hand side so a stress fracture, best check the rest of them as well.
I would look at cutting some tube so it can "clip" around at least the front half to reinforce the area and do the other brackets as well, I
guess running rose joints rather than rubber bushes has increased the shock load.
When I looked at my mud guard stays they had started fracturing like this.
If you cannot weld bring it around to mine with a bottle of red wine 
Regards Mark
[Edited on 26/5/14 by mark chandler]
The tube is to thin to take suspension loads.
Suspension load should always be on intersections, where tubes meet, unless the section is thick enough.
Any news on wether this is an mnr, mk or alike?
Bit worrying
Looks like a combination of dodgy design and poorly welded (or not properly treated) welds. A) you shouldn't be loading a beam in the centre like
that and b) it's clearly a brittle fracture of the HAZ. If the tube had been thicker it might not have failed or might not have failed so soon.
If the weld had been properly treated to not be brittle the tube thickness may well have been perfectly acceptable.
Incidentally all failures are stress fractures...
Also, looking at the bracket shape, it looks like the bracket has been crushed (i.e. spacers/top hats too narrow for the gap) - could be a camera
angle but that loading on top of everything else may not help.
[Edited on 27/5/14 by coyoteboy]
It's enticing to take large amounts of kerb at Anglesey at speeds that are frighteningly fast, perhaps you were?, perhaps that was the last straw
for what is not an ideal bracket on a round tube.
Fatigue break.
It it was mine I'd be looking at the other side, then the other end, very carefully. Actually, if I had that sitting in my garage right now, a
piece of 1" square 16g tube would be going in.
I've never actually measured it other than look at it after i've drilled a hole in it but I would guess that the square tube in my Dax Rush mush be around 2mm or maybe just under in terms of thickness. The engine mounts I made are 4mm thick. That tube does look too thin for heavy loads too me.
quote:
Originally posted by MK chippy
Any news on wether this is an mnr, mk or alike?
Bit worrying
The chassis is an inboard MNR
2000 miles, 2 trackdays. MNR have been helpful to a point.
There was no kerbs. I had never been to Anglesey and was feeling my way round.
I'm abit narked by this as it's my second MNR and both have had problems.
The last one had a habit of breaking rear wishbone mounts where the bracket had been welded to a round tube!
[Edited on 27/5/14 by gaz_gaz]
quote:
The last one had a habit of breaking rear wishbone mounts where the bracket had been welded to a round tube!
Slightly OT, but its a common misconception that T45 needs post weld heat treatment, provided the correct filler rod is used
and the material is under 3mm thick then no heat treatment is required.
Ideally TIG would be used to weld thin gauge T45 with A15 or A18 filler rod. You could of course bronze weld with either an oxy acetylene flame or TIG
as the heat source, many bicycle frames are made this way, as were the old Caterham chassis made by Arch.
I don't think either of the above processes would be cost effective for a small locost manufacturer of Se7en chassis though, they tend to use MIG
for speed and ease, although i don't know many that use T45 either, again on cost grounds.
Years ago my pal bought a Streetfighter frame for his FJ1200, it was made from chrome moly tube and fully mig welded
it lasted 50,000 plus hard miles before one of the down tubes cracked round an engine mounting bracket, he brazed it up and
AFAIK it never cracked again.
Al 
Have you spoken to mnr? Just wondered what their advice would be to get over this?
Dave
Would have been better if the bracket wrapped around the tube rather than just welded onto the face or the tubes where the suspension was mounted were
thicker than the rest, or both
My nissan has thin wall tubes like that for its trailing arms at the rear, which are just fine so long as the bushes on the ends are free to turn, the
second the bushes start to seize….SNAP!
quote:
Originally posted by designer
quote:
The last one had a habit of breaking rear wishbone mounts where the bracket had been welded to a round tube!
There would seem to be a design problem!
quote:
Originally posted by MK chippy
Have you spoken to mnr? Just wondered what their advice would braced ul over this?
Dave
I remember that another Locoster had the same problem a couple of years ago.
It's irrelevant what year the chassis is; it broke!!
I'm quite shocked at just how thin the material at such a load bearing part of the chassis.
As someone who has never constructed a chassis, is that the normal gauge material to be using? Is that what all the more well known kit manufacturers
are using?
Luckily no one was hurt you were on a track day and it didn't happen on a road with no run off etc.
Dave
quote:
Originally posted by sdh2903
I'm quite shocked at just how thin the material at such a load bearing part of the chassis.
As someone who has never constructed a chassis, is that the normal gauge material to be using? Is that what all the more well known kit manufacturers are using?
Far from being a first and a one off.
Howmany have had the rear brkts fall off 3-4 and this is what the 2nd - 3rd where the front brackets / chassis have given way. !!!
quote:
Early possible causes are according to them are.
incorrect toe or camber
incorrect corner weights.
seized rose joint
previous accident damage unnoticed.
What isn't a cause according to them is
Tube thickness
welding quality
bracket location
Unfortunately yes.
So, running a certain degree of Toe or camber might cause a suspension bracket to rip off?
What are the limits? 2deg? 10deg? 45deg? 180deg?
Same goes for corner weights.... if the car is so sensitive to such small changes then it isn't safe on the road.
Never heard anything so pathetic.....
Although to be fair the other options, seized rose joint and previous accident damage unnoticed, are certainly more probable
[Edited on 28/5/14 by Alfa145]
Looking at the photos of the chassis on the MNR website, it appears that this type of bracket is no longer used at the front. It looks like it might still be in use to the rear though, so it would be good to hear the official word from Marc or Chris on this particular matter.
Hi all just to state a few facts:-
We have been in contact with the current owner to try and ascertain what has happened,
obviously it is easier to diagnose seeing the car rather than just a couple of pictures:-
However rather than jump to a conclusion all facts have to be examined, and possible causes investigated
So we asked the following:-
copied and pasted email below
-------- Original message --------
From: Chris Nordon
Date:27/05/2014 20:00 (GMT+00:00)
To: "Gaz ."
Subject: Re: MNR Broken suspension
Hi Gary
What settings did you use-ie camber and toe?
Rgds
Chris
Please note this was a question asked to ascertain the facts
and not as a member on here has suggested stated as a reason for failure,
however incorrect setup can be a possibly contributory reason for failure.
This is to make sure the car is running correct geometry as this is a fully rose-jointed car
and if the cambers / toe / ride-heights are excessive then rod-end lockout is a possibility.
The car in question is an early race-car / track-day car which is a circa 2004
car despite the car showing an 08 plate.
As the car is a race-car it has a mix of tubing 1 inch, 3/4 inch od with varying wall thicknesses throughout, 16 and 18 gauge
and is subject to the usual tolerances of tube manufacture:- wall thickness tolerance of -10 % and anything up to + 18%
and outside diameter tolerance of -0.4mm to plus 0.8mm
As far as we are aware and can remember we have not seen this car since 2008
( please bear in mind we are a medium sized manufacturer so produce up to 100 cars a year ) so can only recall histories of cars
if we have documented correspondence / have a history of supplying parts.
we don't have a great deal of notes about this particular car so cannot be sure if the car has had any maintenance history,
or even give any history regarding possible accidents / usage. This is not uncommon with a car of this age, as some cars just
disappear off the radar completely or are on the 6th plus owner / have been maintained or have been fixed elsewhere
And in some cases there are cars that loose their identity by being exported or re imported.
So far we have been asked to identify why it has broken based on 2 photos and being told it has been at anglesy race track
this is the only information since 2008.
So based on that information all we can do is ask for as much information as possible,
ultimately we need to inspect the car
It could well be that all the rod-ends are nearly 10 years old and have an element of wear and play depending on usage
or even it has been involved in an accident and has been fixed by a previous owner / user or even a third party garage,
( as the current owner is now considering )
The current owner has confirmed that the setup is in the ballpark of a std car - have previous owners been as prudent in checking ???
we simply do not know.
All i can comment on is 2 pictures, and all i can glean from those is one shows a loose rod-end lock-nut,
which will allow a twisting force under heavy braking, is this maybe an indication of a lack of previous maintenance??
Also it appears that the suspension bracket is pinched in and the sides are not at 90 degrees - so indicates that there could be
incorrect spacing, which would create stress on the bracket.
Having spoken to the current owner it would appear that there is a washer behind the rod-end lock-nut which indicates
this wishbone has been removed at some point ( as there is no washer fitted to that location ever )
The wishbone appears to have been removed and then been incorrectly refitted or even replaced ??, this could be for a variety of reasons:-
1. To re-powdercoat wishbone due to stone chips etc
2. A worn rod-end has been replaced
3. A new suspension arm has been fitted due to damage
Comments regarding previous failures should be considered on their own merit and supported by facts of individual cases and
not hearsay. As an example about 5 years ago :- we had a customer who alleged a bracket had failed whilst on a track-day.
Yes it did...... after he had made heavy contact with a barrier which a YouTube clip found on the internet substantiated.
I am not in anyway suggesting this is the case with the current owner before anyone comments that is the case,
the fact that sometimes people don't always give the full picture and just an edited version of events.
how many times have you seen the fabled words low mileage and one careful owner on an advert for a used car
( not just kit-cars but all cars ) and they turn out to have a hidden history.
Without an inspection of the car these are the only conclusions we can make on evidence provided
We have asked the owner to bring the car to us for inspection and a full health check,
so we can get some answers rather than speculate.
Once we have done this i will happily update this thread with findings and the outcome,
however i will not get involved in a debate, with other manufacturers or anyone else for that matter based on
2 pictures and hearsay or not knowing the full facts.
Best regards
Marc
that seems an extremely fair and accurate statement from Marc imho. Any racer chassis that's lasted 10 seasons is doing well given the
'ammer they get!
cars used 'hard' on the road suffer far less than a race car, irrespective of what owners think. Generally racers use stickier tyres, and
the cars loaded to the max in a corner amd then you take a big chunk of curb to get the times, amazing the bloody things hang together as long as they
do.
a friend races Caterhams and they 'life' the chassis's, irrespective of damage, either whole cars sold on or a fresh chassis fitted
over the winter.
all my opinions of course and no allegiance to any 7type manufacturer, just a happy club hillclimber that batters the sh*t out of everything owned lol
it would be worth getting the other suspension point welds dye penetrant checked for cracks just for piece on mind and some new rose joints
Seems to be a fair comment from MNR. You never know where a secondhand car has been before you buy. I know a fella who bought a Anniversary Edition
Golf MK4 GTI. It had about 50K on the clock. Coppers turned up one day and told him his car had had the clocks altered and in reality it had 254K on
clock!
That MNR could have seen some heavy racing.
im not sure how the dye penetrant works with powedercoating or paint finishes, most single seater wishbones are passivated or chemically blackened in
some form, so works well on those, maybe Marc or an engineering type has a view?
as for rosejoints, unless changed in last 12 months, change the lot and keep as emergency spares or better still, sling 'em. anything less and a
repeat performance is quite likely imho
if no bills from PO, then change them. Beware of cheap rosejoints too, there load ratings and liner type may not be suitable for all areas on the car
I've spoken with Marc today and cleared up a couple of misunderstandings..
My intention was never to rubbish MNR or there product with this thread.
I only wanted an opinion from knowledgeable people.
I do feel it's worth mentioning that the chassis wasn't raced for 10 years solid.
It was raced but how much is unknown and used for trackdays and shows such as kitcar live at Brands Hatch from 2004 to 2008
What I do know is that it's never been raced since 2008 but has done a few trackdays although no previous owner has admitted to knocking the
car!
We are working towards a solution and will hopefully get to the bottom of this failure soon!
Did you ever get to the bottom of this?