C4.1 Chassis
 

Been to chadderton today and was told that some of the c4.1 chassis had bent:confused: how bad were they bent? and was it just through the jumps or was it due to a bad crash? either way surely this shouldn't be happening?

Hmmm.

Saw lots of people looking and analysing one and heard that Steve had to adjust his last time with a hammer !

Doesn't sound promising, anyone shed some light ?

if the chassis is made from 5251-H22 aluminium and is unsupported between the steering bulkhead and the batteries then I wouldn't be at all surprised. if that material spec is correct (from the CML website - link below) then IMHO it's totally the wrong material....waaayyy too soft for the application. it is cheaper than 6082-T6 aluminium I suppose and is easier to bend (from a manufacturing point of view) but an incorrect material choice for this design.

http://www.cmldistribution.co.uk/new...iew=0000001811

So then my next question is if this is not a suitable material are cml going to send us all a chassis that is going to work properly?

not my call. If it was me I'd be asking (a) where the chassis bent, (b) what the material spec is, (c) what were the conditions that caused the chassis to bend and (d) is this an isolated incident or a reoccurring problem.

That material is used because it flexes not because of cost. The fact it's cheaper is a bonus. I know that when the car was being tested at the beginning of this year different grades of aluminium and cf were tested.

(The CR2 chassis and motor plates were made from the same material as the C4.1)

Steve bent his chassis at the last Chadderton meeting because he hit a car flat out on the straight, if it would have been a b4 then the chassis properly would have broke IMO.

I had some pretty big crashes today and just kept a eye on my chassis using a steel rule and it's fine

controlled flex is fine but staying bent is not - the material (if the spec is correct) is too soft IMO especially when the chassis is totally unsupported between the steering and the batteries. there is a reason why most chassis have some vertical webbing or support in that area.

the cr2 chassis was supported and braced with CF as far as I know.

Nick, think your trying to point something out about the car that is just not the case and I am sure that CML would have not released the car if there were issues during testing with chassis bending.

If you added webbing or stiffened the chassis then this changes the cars total characteristics with regards to handling.

The results of the car speak for themselves top three in nationals and I am sure phil sleigh was in the top ten too.

Yes it the CR2 had side pods (pods were not cf)

Mine had different pods infact jonathan and myself had developed new side pods which were smaller to try and help generate flex. As it happens the shell was not such a good fit so they were never released.

From memory I think the cougar aluminium chassis has no side pods? Although it does have a top deck which is made of plastic and has lots of flex. Not 100% sure though.

the cr2 chassis was supported and braced with CF as far as I know.[/QUOTE]

agreed - the results do speak themselves and there is no denying that fact. also agree that changing the flexibility of the chassis has a significant effect on the handling of the car (assuming no other changes).

the one thing I would say is that there is always a risk that no matter how much testing you do, when you release the product into the wild you will sometimes find issues that were not apparent during development no matter how vigorous your testing procedures were. I know this from personal experience and never cease to be amazed how the general public find weaknesses in your products you never anticipated.

I'm old enough to remember having to straighten the aluminium chassis rails on kyosho scorpions.....!!

Yeah agreed mate

Exactly. F1 drivers don't drive like blind, handcuffed monkeys, yet the blind, handcuffed monkeys are the ones that find the weak spots.

yes I agree to this as apple the biggest ever for par with the iPhone 4 grip of death they had testing models cased in a 3GS shell so problems never occurred if they can get so so so wrong anybody can I think you will all agree

I guess anything will break if its hit hard enough...

CML could of made the chassis bomb proof, but it wouldn't handle half as well, I know what I would rather :p

Ben

No what is being said here is there are weak links to all products but the chassis should not be this a twisted chassis after a colision = garbage in my book there should be given flex or out and out strength these days my b44.1 could hit a wall at 30 and bounce of that's the point

Its a piece of flat metal it will bend if hit hard enough! Solution is, buy a spare chassis! Or sell the car and buy a brick! I wish my real car would survived a high speed impact, but I guess BMW have not found a way of making metal that doesnt bend yet.

It just need a brace from top of front cell mounts, to the front brace. To thin strips of CF would do it. Would still give twist flex, but reduce kickup flex..

Mine bent by 1-2mm, but I did have a few lairy moments on the straight... and it bent back with my knee easily. I would have expected it to have bent, I didn't feel any effect on the track, the car felt great!!! :thumbsup:

So...
Anyone know if spare chassis are available ?
How much are they ?

Bloody hell Chris, not good - id be gutted !
Won't it be weakened now ?

an identical replacement chassis won't resolve the issue of the material choice and lack of bracing in that area. if you look at the relative 0.2% proof stress of 5251-H22 aluminium vs 6082-T6 aluminium it'll be apparent why.

having said that, in my (very) humble opinion, a change to a stronger material will not resolve the fundamental issue of a lack of bracing in that area.

daz - you're right - everything will break given enough effort - i think the question is not so much the extreme events causing damage more would everyday racing incidents cause the chassis to bend that itself would not damage a more 'conventional' moulded / braced chassis ?. not many people expect to carry a spare chassis around with them nowadays and having to check it for straightness after every race would get pretty tiresome pretty quickly.

just my 2p's worth

buy hey - everyones an expert online & after the event eh ?! :)

Thats a good idea, but when all the radio gear is installed theres not much space left, only enough to fit a couple of pubic hairs. They need to go down the old Cougar route and form a chassis with sides, I never saw one of these bend.

Or a Mardave Cobra. I've seem people putting tent pegs in the ground with them.

Chris, how do you know you bent your chassis 1-2mm ?

T

so who wants a cf tub? *ducks as flames are thrown* :p

already got a mint AC S2 - funnily enough i've not bent that one.....:) :)

I'm sure there will be a nice AC chassis available in the near future :D

Bullshit, they could make it so other did not bend as easy but to help prevent you dying they create crumple zones which are designed to bend.

Who makes the standard chassis?

AC was involved in the design of the centro but I'm not sure if they had something to do with the production.

I'm talking about a AC optional carbon chassis.

Did they make crumple zones on the Titanic?:yawn: Or could it be that CML have thought this through, and have built a chassis with crumple zones to protect the delicate electrics?

I really fancy getting a Centro - but £160 for a few bits and a sheet of metal - that could bend in a crash seems a bit steep to me. I know I will only end up bending it if I run one...

It shouldn't bend - if it does / is found to bend, then as Chris has said, maybe it needs some bracing to the front or side rails to stop front to back flex ?

What we found out with our car as that if you over tighten the battery strap turnbuckle on the battery brace it will flex the chassie.
Just loosen it off and it will flex back.
Also you need to lift the battery post so that they sit inside the battery strap holes.

The more I'm thinking about it the more I realize people that said "forget about RC gods, lets wait until it gets into the hands of "mortals" were absolutely right

Before I consider placing an order and bearing in mind I crash a lot these days...

losi 22 chassis is 2.5 mm in 7075 T6 circa 500 MPa proof strength. C4.1 is 5251 H22 circa 170 MPa, what is thickness of C4.1 chassis?

and the Losi 22 is formed slightly at the edges plus the side pods tie into the front bulkhead. 7075-T6 is stronger than the 6082-T6 i originally suggested (approx. 310 Mpa proof stress) but either material makes the 5251-H22 seem a little on the weak side.

i still maintain that irrespective of what the material is, some form of bracing is required - be it formed edges on the chassis or some upper bracing - it just doesn't look right at the moment IMO and you know how the old saying goes.....

I was comparing with the 22 as I've not heard of anyone bending one, although some say its too stiff from a handling point of view.

In the future in RC cars maybe compliance will be introduced in a more robust and controlled way as per 'real' cars, subframe or wishbone rubber bushes.... would offer scope for tuning too..

Think I will see how many slightly ham-thumbed people such as myself bend them...

what's the cost difference between those three types?

Vega! :p lol

The reason i started this thread is because i am one of the mer mortals that will crash quite alot and what i'd like to here is that there will be either an alternative or something else that can be added to the car to prevent this, after all £170plus doner car isn't cheap and i would've thought they should have given the car to a noddy like myself to test
Aswell as a pro then they could've made sure it's all gravy. I really like the car but it doesn't exactly inspire confidence.

the car has been run by a " noddy" as you put it :-)
and ran with out issues !
The reason this car works so well is party because of the chassis and the way its designed , the other manufacturers that have stiffer chassis dont work quite as well .