Where do I start! I'm trying to model a standard chassis in CAD but the pictures and dimensions do not make sense as I already knew but even the visuals don't add upPage 54 of the new book shows a isometric view of the rear chassis, W2 at the top seems to go to the inside of the vertical plate on one and the outside on the other and both meet RU2 at the bottom which would be impossible if using the dimensions on page 51. The 813 and 965 dimensions add up with the 2 25mm rhs of RU2. I think what has happened is they're have been a few various designs of chassis lying around Ron's workshop and he's got his measuring tape out on all them at different times. I think it's a case of just choosing one and set of dimensions and making up your own, but that also means one persons dimensions won't suit anothers if they've used different references.

Small example, F1 & F2 will need to made longer of J1 & J2 shorter if you plan to use the plan of front chassis member fig 4.10 on page 49 otherwise LD won't mate properly with F1 and F2, check out my drawing in the pics section. Fig4.10.jpg

I experienced the same frustration when working on my CAD models... and I think you are absolutely correct that Ron used a bunch of examples from many different builds.

Regarding W1/2... The most common solution I've seen is to set them on the inside edge of the 4x4 plate (inside of the gusset) and then angle them downward to the end of RU1/2 (as you've noted). Technically, that is a compound angle... but Ron's approach to such subtle issues seem to be based on a "grind to fit" approach.

You're welcome to refer to the drawings on my website for my interpretation. Like you've suggested... it's not necessarily the right answer, just another view. You'll have to decide how you want to build it for yourself eitherway.

Cheers,
-Jim M.

I think that's been part of my problem too, I've been using the metric measurements, which aren't accurate enough, and designing the chassis using those. I've tried to avoid compound angles as much as possible and at the moment its only on LA, LB & Z. O2/3 are attached to K3 instead of O at the top and W1/2 are parallel with the centre plane.

Myself and Mark D have completed the model and we just need to create the drawings for each member and plot out a full size plan to paste to the board as a guide, to ensure accuracy.

I would like to thank you for your drawings, they are very good and we referenced them quite a lot when we were querying the book. Thanks
Dunc.

Cheers Dunc!

I'm glad to hear the drawings where helpful... it's good to know they had value and that makes it all worth while.

It's also really helpful to hear ideas on modifying the design. I too have made W1/2 parallel to the center plane in design that I plan to build. I hadn't considered 'straightening' O2/3 to meet K... but I like the idea (Ta!).

An idea you might want to consider is placing RU1/2 horizontal to the ground. This will provide more room for the rear axle to travel while airborne (yippie!) and it also allows for a non-compound Z. You can see how I accomplished this in the latest 3D model of my "work in progress". http://mcsorley.net/locost

I also switched most of the round tube in the rearend for square, and most of the square tube for round. It should be easier to build and easier to form the ally around (assuming you have a tubing bender).

Regards,
-Jim M.



regards,-jim m.

I'm going the IRS method with my own chassis which is wider and taller than the book, I created a second model to help some of the guys on the list in response to the book errors questions. I'll post a couple of jpgs in my wee folder thing to show you the O tubes.