stig mills
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| posted on 1/4/09 at 03:15 PM |
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I do not divulge info re my consulting engineers. That would be very useful to my competitors. Around 40 Rockets have passed SVA though so dont worry
I think my guys know what they are doing. They design roller coaters and fair ground rides too. The documents relating to my products have phrasing
like "plastic redistribution of moments".
The other approach is to look at it, use logic and add a bit in if your not sure if its strong enough. Add weight though. Make it too stiff, watch the
welds crack after it's been in service for a while and then get an expert in. How many manufacturers produce 60 odd pages of calcs to show
potential customers? No I,m not posting them on here! Lots of builders turn in to experts when they have had a little experience and no formal
training and small experience. Problem is if you build yourself a one off it can cost more than the car costs to have it designed by pro's.
Maybe a problem but it does mean cars can be heavier than they need to be. Use a cad system such as Robot and it will only produce info based on your
input. That can mean garbage in garbage out.
The Rocket forinstance has seat belt mounts made from 6x50mm plate welded to a 50x3 CDS tube. Not exactly inadequate. Your internal organs cannot
stand anywhere near the loads that the Rocket seat belt mounts can!
Regards Stiggy
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cloudy
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| posted on 1/4/09 at 04:04 PM |
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An average human in a 30mph crash with a relatively immobile object such as a tree or wall produces about 2.4 tons of force on the seatbelt mounts.
Perhaps an oversimplification but divide that by 2 for a 4 point harness with the top mounts together - 1.2 tons
If that 6x50mm plate is just welded to one side of the tube then I can guarantee that force will arc it down to crush the tube and then tear off
around the HAZ. SVA requires the seat mounts to go right through the tube and weld both sides in this situation, so if this is the case it has a
fighting chance however the undercut weld at the front side suggests otherwise...
James
[Edited on 1/4/09 by cloudy]
www.warnercars.com
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stig mills
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| posted on 1/4/09 at 04:35 PM |
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The SVA inspectors have all passed the top seat belt mounts on many occasions. This just goes to prove that experts and self acclaimed experts
opinions differ. No one who has commented on this point has examined the vehicle, an expert would not voice an opinion without carrying out a full
investigation.
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Staple balls
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| posted on 1/4/09 at 04:44 PM |
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quote:
Originally posted by stig mills
The SVA inspectors have all passed the top seat belt mounts on many occasions. This just goes to prove that experts and self acclaimed experts
opinions differ. No one who has commented on this point has examined the vehicle, an expert would not voice an opinion without carrying out a full
investigation.
Give me a car to inspect and crash into a wall, and I'll give you an expert's opinion.
Until then, that seatbelt mount looks a bit iffy to me.
[Edited on 1/4/09 by Staple balls]
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cloudy
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| posted on 1/4/09 at 04:46 PM |
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I sense more than a hint of annoyance in your tone, I've never proclaimed myself as an expert! I think your products are great and of a very
similar mindset to my project - I notice your chassis has had a previous incarnation on your website - presumably this arrangment was changed as a
result of the investigation?
www.warnercars.com
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pocket rocket
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| posted on 1/4/09 at 08:17 PM |
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As a mev customer ill just quickly add my 2 pence to this fairly heated thread...
when i read some of the threads on here i start to panic about my build, the last one to cause panic was a thread about pop rivets and if or not they
come loose over time (which means my floor will fall off  )
when i read this thread i started to panic again but then a asked my self this question...
would stuart at MEV design and sell a car with seat belt mounts that could possably fail in a crash and kill the driver (i.e me), my girl friend or
any of the other 50 odd rocket owners out there????
i think the answer is obvious isn't it!
Dam...iv consused my ability with my intentions!
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cloudy
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| posted on 1/4/09 at 08:39 PM |
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The intention was not to cause panic, more to highlight something that just visibly looks to be insufficient (especially on the chassis
pictures on the website)
As potential customers are noticing, it might be worth MEV posting up the test results to put everyones mind at rest?
www.warnercars.com
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pocket rocket
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| posted on 1/4/09 at 08:45 PM |
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I understand what your saying mate, but if stuart say's its safe then thats good enough for me!
I don't think any kit car company would sell a car that is sub standard in the way of safety.
just like you, i would be happy to weld my own chassis and drive a car that i had welded but i wouldn't feel happy with welding a chassis for
someone else just incase something happened or i hadn't done it right, im quite sure kit car companys like MEV go to great lenths to make sure
all aspects of there car's are safe before they sell to customers.
Dam...iv consused my ability with my intentions!
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cloudy
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| posted on 1/4/09 at 08:56 PM |
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Just think it would be more beneficial to us (and MEV!) to quote an estimated positional deflection against a factor of G and a maximum loading rather
than:
"The documents relating to my products have phrasing like "plastic redistribution of moments" Which frankly tells us nothing!
www.warnercars.com
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Paul TigerB6
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| posted on 1/4/09 at 08:56 PM |
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quote:
Originally posted by pocket rocket
I don't think any kit car company would sell a car that is sub standard in the way of safety.
Best not mention the particular Robin Hood model that some SVA testers were refusing to test due to their dodgy design a few years back!!
I can see where Cloudy is coming from myself - would that plate really withstand the strain from a 100kg person stopping at 25G which is easily
achieved in a crash??
Are the lads from MEV willing to publish the analysis just on this particular part of the chassis??
[Edited on 1/4/09 by Paul TigerB6]
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Staple balls
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| posted on 1/4/09 at 09:15 PM |
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quote:
Originally posted by Paul TigerB6
Best not mention the particular Robin Hood model that some SVA testers were refusing to test due to their dodgy design a few years back!!
Oh god, don't remind me.
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MikeR
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| posted on 1/4/09 at 09:36 PM |
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What about the dutton amphicar that was according to a judge last year - a death trap. Seem to recall their was a jail sentence being threatened for
that one.
As I said before - I'm no expert and have learnt most of what little i know via reading on here.
Would a kit car manufacturer knowingly do something that put a customer at risk - not likely unless they where morally bankrupt. MEV don't sound
like that at all - the fact they've gone to the effort to pay someone to analyse the chassis is a very positive act.
At the same time - mounting your harness via a lump of steel that is going to try and twist / lever its mounting in an accident .... with no
engineering experience, doesn't seem right to me.
I don't think people are asking for the complete analysis (ok, i'm sure we'd all love the complete analysis as we're all a
bunch of car geeks) but something covering the seat belt mount would be welcomed by the engineers and non engineers alike.
As for the comment about floors and rivets - loads of people have the floor rivet on, probably (complete guess) 70% of people on here. They do fret
and over time it is a possibility the floor will drop out, just like with a welded floor where there is the risk of water getting in and rotting the
floor out. You make your choice and you take your chances lots of years time.
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mr henderson
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| posted on 2/4/09 at 07:58 AM |
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That seat belt mount looks OK to me. I think all this stuff needs to have a context, and the context here is a small lightweight car. The light weight
is particularly important.
I assume that the seat belt mount in question has been designed in that way because the mounting point needs to be where it is, and the bar it is
attached to needs to be where it is, and if the bar was moved to make the mount 'look better' that would seroiusly compromise the overall
design and add weight to the structure.
What we need to know is whether or not the solution that MEV have adopted is adequate. It certainly appears so to me, and I'm sure that, were I
about to purchase one, and went to the factory, that Stuart would show me the relevant part of the report were I really concerned about it.
Another point worth considering is that, were the worst to happen and I be in the car during a serious collision, whatever force went into deforming
the seat belt mount would be force that would not be going into me
John
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Mad Dave
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| posted on 2/4/09 at 08:39 AM |
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Mr Henderson, I'm confused. Are you saying you should think about the aesthetics & weight over safety?
In an accident the forces transfered to that mounting will be at some sort of angle to the centre line of the car. That plate will bend and the welds
will probably tear
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mr henderson
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| posted on 2/4/09 at 09:20 AM |
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quote:
Originally posted by Mad Dave
Mr Henderson, I'm confused. Are you saying you should think about the aesthetics & weight over safety?
In an accident the forces transfered to that mounting will be at some sort of angle to the centre line of the car. That plate will bend and the welds
will probably tear
Where have I mentioned aesthetics?
Are you really serious about the weight over safety issue? That must have been a joke, or maybe you would be happier on the Rolls Royce owners forum
(running RRs can be had for less than the price of a decent 7)
Of course the plate will bend, it might even tear. There will be a lot of other stuff going on as well, some of it quite unpleasant. I think though,
on the whole, I'm going to go with Stuart rather than your 'probably'
John
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stig mills
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| posted on 2/4/09 at 09:21 AM |
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I pulled out some calcs I had done for a roll bar. I used a 33mm CDS tube as a horizontal member with 4 top harness mounts on it. My engineers report
showed it as being inadequate and so I changed the design b4 selling any. I have attached a small part of that report as proof that we do it properly
and that none of you should have any concerns. I pay £1000's for this kind of report and do not wish to assist competitors with it by posting
it. I do not take the "lets weld another bit in to make it look stronger approach" That just adds weight.
Interestingly if you look at the Haynes Roadster it uses a 33mm top roll bar tube that has 4 harness mounts on it. Exactly the same as the one I dont
make.
[Edited on 2/4/09 by stig mills]
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stig mills
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| posted on 2/4/09 at 09:46 AM |
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[img]<a href="http://s666.photobucket.com/albums/vv25/stiggymills/?action=view¤t=img040.jpg"
target="_blank"><img src="http://i666.photobucket.com/albums/vv25/stiggymills/img040.jpg" border="0"
alt="bar calcs"></a>[/img]
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Mad Dave
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| posted on 2/4/09 at 10:10 AM |
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Those calcs are interesting. That section relates to the moment applied to the diagonal rollbar brace and shows that max force is approximately equal
to a 100Kg man decelerating at 7g.
I hope that further down there are calcs to show that the plate welded to the diagonal is adequate enough. I still think this will be a plastic
hinge
John, my 'probably' is based on results from Ansys. I trust Ansys rather than Stuart
[Edited on 2/4/09 by Mad Dave]
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cloudy
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| posted on 2/4/09 at 10:42 AM |
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Stewart this is not coming across well - I suspect most will now think you are avoiding the issue, posting a report of a design you haven't used
is completely pointless.
Why not just post the small section of report that states the calcs for the actual setup? The statement "do not wish to assist competitors with
it by posting it" is frankly bull, and we both know it.
www.warnercars.com
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stig mills
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| posted on 2/4/09 at 02:01 PM |
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I posted the calcs ref a bar I dont use as they are of no use to me. Happy for anyone to see those. They are not for a current MEV chassis and do not
relate to a diagonal tube. The calcs show the Haynes Roadster tube as inadequate as a case in point that everyone does not get it right.
Over 40 succesful SVA tests and documentary evidence of structural integrity gives me complete confidence in my products. That said if a potential
customer wanted me to supply a car with alterations to say a single hoop or 4 point mounts or a different engine option then I would always look at
it.
One off bespoke cars are always considered. We do all our own pattern making, GRP laminating and most of the fabrication. We also guarantee structural
integrity and produce documentary evidence for customers who request it.
Thank you for the exposure. Stiggy
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cloudy
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| posted on 2/4/09 at 02:20 PM |
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Not the stance I would have taken, but that's your call to make, my opinion of MEV has definitely changed somewhat
www.warnercars.com
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mr henderson
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| posted on 2/4/09 at 03:09 PM |
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quote:
Originally posted by cloudy
my opinion of MEV has definitely changed somewhat
Mine hasn't. I'd buy one tomorrow given the appropriate amount of dosh (and a quick check to make sure I could get in it)
John
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Paul TigerB6
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| posted on 2/4/09 at 03:32 PM |
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quote:
Originally posted by mr henderson
quote:
Originally posted by cloudy
my opinion of MEV has definitely changed somewhat
Mine hasn't. I'd buy one tomorrow given the appropriate amount of dosh (and a quick check to make sure I could get in it)
John
But you could get a whole lot of Subaru for the same money (and you'd definately get in it)!! I thought from one of your previous threads you
thought things "had gone wrong" now that kit cars arent at a really low price??
Personally though i'd have to say i'd have one too (still not sure about that seat belt mounting point so would want to see the report). I
thought the MEV Rocket was the best car at Stafford last year but think this new Atomic could be even better so hope MEV are at Stoneleigh. I think
its great that a manufacturer is actually looking deeper into the structural design even if it does mean the kit is a few quid dearer.
Still, shame we cant see a few figures about what that single plate for the seatbelt mounting point will actually withstand. Saying its passed an SVA
doesnt make a bit of difference to me - SVA examiners arent structural engineers (as far as i know) and they arent putting their life potentially into
the hands of that one bracket.
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mr henderson
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| posted on 2/4/09 at 03:51 PM |
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quote:
Originally posted by Paul TigerB6
I thought from one of your previous threads you thought things "had gone wrong" now that kit cars arent at a really low price??
Not really, still, it's always difficult to 'interpret' people's meanings. I don't remember saying that I had gone off
kit cars and woulndn't have another one, what I was reflecting onn was the way the business has changed, and I do seem to remember summing up
with the thought that it was the competition had got a lot cheaper, rather than the kit cars having got a lot more expensive.
John
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MikeR
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| posted on 2/4/09 at 06:26 PM |
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taking this sideways a little..... I'll be fitting a roll bar soon and was going to do something similar to the haynes roaster. My plan was to
use 2.5 inch RHS of a random thickness and weld on the harness mounts at the rear of the box section (like on the floor).
Thoughts on this approach / thickness of steel to use? I was guestimating 2mm should be fine so would probably go for 2 to 2.5mm. The roll bar will be
2.5" and 3mm (or it may be 3" and 2.5mm I can never remember).
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