FF3 and suspension bracket

[voucht]

Hello,
I have a concern about the front frame, and I'm wondering if I'm completely wrong, or if there is something I missed ?
If the front and back face of FF2 and FF3 are respectively parallel to the front and back face of FF1 on their lower part, and if the top part of FF2 et FF3 are square on each face with FF4, then the outer and inner face (leaning part) of FF2 and FF3 can't be parallel to the outer and inner ends of FF1, as their base section, when cut and put flat on FF1 is a rhomb (see 2D sketch below). Stop me now if I'm wrong.
FF1-FF3Problem.jpg
But if I'm right, how the axis of the suspension brackets attached on FF2 and FF3 can be parallel to the central line of the chassis, as the back plate of these brackets should be welded on the outer side of FF2 et FF3 which is NOT parallel to the centreline of the chassis ?
On the 3D view, the axis and back plate of the bracket is parallel to the centreline, and the back face of this bracket cannot be plated to the outer face of FF2 or FF3. There is a gap, as the two faces are not parallel.
My guess is when you put the suspension brackets with the rigs, you cheat and fill the small gap with welding. Does not sounds very good to me, but I might be worrying for nothing.
GapOnBracketAndFF3.jpg
Could anybody who has already been to this point please explain what he did, and the magic trick ?
Thanks a lot.
Regards.

[michael92]

I belive this to be normal, when discussing this with handyandy he said most times people need to use packing plates

hope that clears a bit up


Michael

[ayjay]

That worried me too.I was convinced I'd got it all wrong --measured a million times, checked the jig etc --- then just welded in a little packer and put in a couple of support fillets where it overhangs the chassis tube

[voucht]

Hello,
Thank you so much for your answers, they confirm me the positions of my FF2-FF3 are right (whew !)
Sorry, I'm not English, and I have hard time to understand what you mean by "packing plate" or "then just welded in a little packer".
Thank you for your clarifications.
Bye.

[Talonmotorsport]

yes you are correct the design in the book is wrong as you have proven with autoCAD. DO NOT NOTCH AND BEND FF3! Make FF3 in two independant sections weld the short upper section to FF4 then add the lower section while in the jig,when you make your front frame jig add two 90' uprights either side of the lower section of FF3 and clamp these SQUARE TO THE BASE OF THE JIG.

[voodoo]

Originally Posted by Talonmotorsport

yes you are correct the design in the book is wrong as you have proven with autoCAD.

Careful mate - you'll get lynched!

[MarkB]

Well, there is room on the naughty step......

[voucht]

Talon (by the way, what is your name, it is strange to call you "Talon"), thank you very much for your reply and the tips. I think I understand what you mean, but to me, it looks like it means recalculating all the cutting angles (especially between the two different parts of FF2-FF3). I will make some simulations with the 3D software first.
... And it is the second time I cut, bend and weld the FF2-FF3 tubes (first try was awful) and I was very happy with the second one
But thanks a lot. It is very helpful.

[voucht]

Originally Posted by voodoo

Careful mate - you'll get lynched!

Woooo scary ! Is it that bad to say there are mistakes on the book on this forum ? I'm new so I don't know the mood here. Sounds sad if it is the truth.
I think it is great, and the author himself should make an update about it. A lot of us use CAD or 3D software nowadays, and we all noticed wrong dimensions. And we see many posts on the forums where people contest the dimensions of the book. It it only for making things better, everybody should be happy about it.
Like I've noticed by drawing the chassis with my computer (2D and 3D) that BR3-BR4 can't be 10° and BR1-BR2 can't be 16° if you want to respect the check dims, but respectively 9.67° and 15.63°. Not a big difference when you cut the tube (who can manually cut a 25mm tube with an half a degree accuracy ?) but it makes a big difference when you draw the map on the board where you are going to position the tubes. Half a degree on a 1 meter tube is a lot, and gives a mistake of too many mm at the end. I noticed it corrected it on my chassis, and I just checked it today on a CAD file I downloaded from a guy on this forum, and found the same result.
Hope I won't go to jail for having said that, No, I just can't believe it...

[voucht]

Originally Posted by Talonmotorsport

yes you are correct the design in the book is wrong as you have proven with autoCAD. DO NOT NOTCH AND BEND FF3! Make FF3 in two independant sections weld the short upper section to FF4 then add the lower section while in the jig,when you make your front frame jig add two 90' uprights either side of the lower section of FF3 and clamp these SQUARE TO THE BASE OF THE JIG.

I've been trying to figure out how to do it (simulating on my 3D software), but each time you turn the tube, or/and change an angle, the complete geometry is modified, and then the suspensions brackets (I mean the axis) will lot have the correct position. Can't figure out how you did it. Do you have any drawing, 3D views, sketches, dimensions and angle cuts you can send me please ? Otherwise I will leave it like in the book, and pack the gap, as it looks like the majority of builder do.
Thanks.
S.