Roadster book updates

[jateu01]

Hi all,

I herd a while ago that there are a few mistakes in book , and I believe there are some updates too.

Can anyone point me in right direction .


Many thanks

J

[skov]

I think this is what you want:

http://www.haynes.co.uk/forums/showthread.php?t=2430

[voucht]

Hi,
It depends which edition of the book you have. The second edition has been corrected.
To make sure, you can check the amendments here:
http://www.haynes.co.uk/forums/showthread.php?t=2430

Good luck with your build :)

[voucht]

Skov, you've been quicker than me :D

[jateu01]

Just trying to throw together a cad of chassis but BR10 is too wide to fit? can any one shed some light on this for me. Thanks to all that replied have changed book info to updates.


J

[voucht]

You can't use the cut angles of the appendix to place the rails BR3/BR4 and BR1/BR2. You need to use the check dimensions p34 of the book. That is, to my mind, why your BR10 does not fit on your CAD drawings.

Why that?

Considering the fact that the author of the book considered that we will draw the layout by hand on a table, using the check dimensions given on page 34 of the book, the exact position angles of the rails are not given in the book. But considering the fact that cutting a tube can not, for most of us, be accurate at a 10th of a degree, the cut angles in the appendix should have been "rounded" to the closest entire value, which, in this respect, makes sense.

Therefore, the cut angles can not be used to place the rails on a CAD layout or chassis modelling, because they hold tiny mistakes, consequences of the rounding of the values in the appendix. These tiny mistakes are acceptable on the cut of the section of a 25mm square box section tube. But if you place the rails according to these angles, theses tiny mistakes are actually multiplied by the lengths of the rails, and at the other end of the tube, the check dimensions are not respected. I hope it makes sense.

The book's datas are not incorrect, they are just not supposed to be used directly with such an accurate tools like a CAD software.

You can check the layout I've drawn (and used on my build table). I wrote the explanations about this necessary correction in English at the right of the layout, and wrote on the tubes, the exact cut angles you can use to properly place your rails in your CAD drawing.
You can open the documents here:
https://drive.google.com/folderview?id=0B-iOekLVikV5NWQ3MTVjNTctNTEzMy00MjRhLWFmODMtNGVjNzA2 ZDg5YWIz&usp=sharing

Or, to make it shorter, consider the cut angles of BR1/BR2 as being 15.667° and not 16°, and angles for BR3/BR4 (and BR10) as being 9.6° and not 10°. With these angles, the check dimensions are respected, and your BR10 should fit. In the same way, BR8/BR9 should have a cut angle of 74.333° at the front end instead of 74°.

These are personal calculations, to me, they are correct, but you might have more accurate tools than me to get even more accurate values considering what's explained above. I don't pretend I've redrawn and redesign the layout and that it is what should be considered as the divine truth ;)

Making a 3D CAD model is a good way, to my mind, to get familiar with the chassis design, if you have the time and skills (and it looks like you do :) ), but if you just need to have a CAD model of the chassis, you can spare yourself the time of drawing it, as there is one professionally done by madis on Solidworks which is really good and freely shared here:
http://grabcad.com/library/haynes-roadster-chassis

Hope this will help :)

[jateu01]

Sylvain thank you for your reply, I am using solidworks to give my self an intimate idea of chassis. The thing is why produce tech drawing that are rough idea of reality . Or am I getting confused ?.

J

[voucht]

Again, it is not wrong, and not even rough if you consider that the goal of the book was not for people to draw the chassis on a CAD software. It was for people to build the car in their garage, and in this respect, the data's of book are good enough.

As I said, the check dimensions are correct for drawing the layout on the table. The cut angles are correct to cut the tubes, because who, building the chassis in his garage with the tools we usually use for that, can make the difference between a 15.667° angle and a 16° angle on a 25mm section?

Wanting to make a CAD model with the book's data is just going beyond what it has been written for, so the book (which can be blamed for other things :eek: ), can not be blamed for not giving us this accuracy. We need to figured out by ourselves !

Just my opinion, of course... :)

[mopple]

jateu01,
if you're done then you can compare your SolidWorks model with those referenced at the Roadster FAQ thread http://www.haynes.co.uk/forums/showpost.php?p=74241&postcount=1 CAD section.

[jateu01]

Mopple first off I I'm not having a go I was confused . The point of using solid works is to compare chassis strength and to evaluate if extra or less rigid chassis required, and with some luck to actually test weather chassis can be lightened ! Now I understand hundreds of cad models have been produced but I'm willing to bet none have been tested digitally. It's not to see if I can draw better its to improve design and maybe even to push to the extremes of carbon fibre build ! So please think before you reply and be respectful not cocky !

And just to reiterate I was and have always been keen to get feedback and advice.

Many thanks

J

[alga]

Spot on, Phil.
https://lh4.googleusercontent.com/-4jfqyNZnqeA/USn2HNG-vtI/AAAAAAAAD24/oGHbsjfvecA/s640/2011-10-01-155938.jpg
Add 8 kg for the tyre and at least 5 for the wheel.

Update: above was a message from Talon in essence stating that weight savings available from the chassis are negligible compared to the stuff that bolts to it.

[jateu01]

Thanks talon you may have saved me hours of research . Has anyone actually stressed the frame to see what it can take . And I don't mean put it into wall. Any advice on v6 power plants ! .

Many thanks

J

[vmax1974]

The way I see it is that the strength of the chassis is in relation to the ability of the person fabricating it. You could be the best computer tech in the world but if your welding skills are not up to the task of welding the chassis the data gained on the computer would be rendered void as the chassis would be better held together with blue tack or chewing gum

[jateu01]

100% agree vmax, although I believe the kit car concept was to open up a new hobby to every one . Negativity only get me driven to finish what I started. It looks like the weight issue is more to do with components than chassis. I hate it when I get the elite attitude from members lol. The point of my exercise is to one build my own chassis but also to see if it can be bettered ! Is that wrong? The only way I can find this out is one spend millions on research or abuse members for there advise .

Many thanks

J

[mopple]

jateu01 a places of interest for you could be LocostUSA and Locost Builders UK forums. There are some quite long topics about seven type car chassis rigidity, weight FEA calculations etc.

[Stot]

Dont the Aussies or NZs have to put their chassis through a stress test before it can be made into a car?

Cheers
Stot

[voucht]

So please think before you reply and be respectful not cocky !

Have I missed something? I don't see anything disrespectful in the previous posts :confused:

[skov]

Have I missed something? I don't see anything disrespectful in the previous posts :confused:

I've been thinking the same thing!

I hate it when I get the elite attitude from members

I'm struggling to see any kind of elitism either!

I'm very confused :confused:

[jason 82]

Should get Ash on here if you are looking at strength of the chassis. I am sure that he said in a previous post that he has got 150 mph out of his Saab turbo powered car ( think the thread was talking about little wings on the nose cone to aid downforce ). A 7 is hardly an aerodynamic masterpiece, so if it can with stand that kind of force acting upon it, then that chassis design has been tested well enough in my eyes. I am using an mx5 1.8 in my car so it suits my needs. A 7 correct me if I am wrong, was designed to give amazing acceleration & the ability to handle like a train. Well that's my interpretation of a 7 any way. I don't think anybody was taking a pop at you, but the more information you can put in your posts, the better. That way everybody is on the same wave legnth. :cool:

[TheArf]

The easiest way to reduce weight in these cars is to stop eating the pies

hear speaketh the chunky fat bu**er

Arfon

[vmax1974]

The easiest way to reduce weight in these cars is to stop eating the pies

hear speaketh the chunky fat bu**er

Arfon

Why did nobody tell me this sooner I have put on 4 stone in the last 9 months

[jps]

I've been thinking the same thing!



I'm struggling to see any kind of elitism either!

I'm very confused :confused:

Likewise - i've found the people who contribute to this forum to be helpful throughout - and don't see what there is in replies to the OP to this thread that elicited that sort of response!