subjated
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| posted on 23/10/16 at 02:09 PM |
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Chassis measurement problem
Hi all.
this may have been covered before but i cant find anything specific in the searches.
im currently drawing up the chassis in cad and have created individual tube sections from the book appendix, be when creating an assembly of the
chassis BR10 end up half way in BR4 and the 924 measurement given on page 34 of the book comes out at 918 on my model, ive checked and rechecked my
drawing of BR3/4 And they are correct, can anyone help?
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Talon Motorsport
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| posted on 23/10/16 at 02:25 PM |
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For what reason do you need to draw out the chassis, there are more CAD versions online of the Haynes than metal ones? Put the computer away and go
and lay the tube out on the build table......
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steve m
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| posted on 23/10/16 at 02:58 PM |
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"For what reason do you need to draw out the chassis, there are more CAD versions online of the Haynes than metal ones? Put the computer away
and go and lay the tube out on the build table......"
+1
Just go and lay the tubes on the marked out board, and start welding, and when you come to weld the diagonals, measure the gap, not what it says in
the book
steve
Thats was probably spelt wrong, or had some grammer, that the "grammer police have to have a moan at
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subjated
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| posted on 23/10/16 at 03:34 PM |
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quote:
Originally posted by steve m
Just go and lay the tubes on the marked out board, and start welding, and when you come to weld the diagonals, measure the gap, not what it says in
the book
steve
i can understand the point both of you are making but something somewhere is wrong, so if im to follow the book/not follow the book, what bit do i
follow the overalls? or the cut lengths?
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jps
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| posted on 23/10/16 at 04:41 PM |
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Incase you haven't found it yet, the Haynes forum has a lot of info including about errors in The Book.
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Slimy38
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| posted on 23/10/16 at 04:49 PM |
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Sorry, it's not the book that's wrong. I've just measured that dimension on my actual chassis and it's 924.
You can even work it out from the BR10 measurement. BR10 long edge is 882. 10 degree angle off 25mm tube is about 4mm shorter each end (874). Add two
lots of 25mm for BR3 and BR4 and you get 924.
It's that 'halfway' bit that doesn't sound right to me. BR3 and 4 end flush with the edge of BR10. What are you measuring as
halfway?
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subjated
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| posted on 23/10/16 at 05:15 PM |
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quote:
Originally posted by jps
Incase you haven't found it yet, the Haynes forum has a lot of info including about errors in The Book.
Yeah have found that and emailed countless times to join up but nothing, and found book errors but not on this subject
quote:
It's that 'halfway' bit that doesn't sound right to me. BR3 and 4 end flush with the edge of BR10. What are you measuring as
halfway?
the Br5,6,11 and 12 "square" measures correct but when i join Br3 and 4 to br11 the overall dimension where br3 and 4 would meet br10 ends
up at 918mm
so br10 end up "halfway" (its actually about a quater) inside br4 when i join br10 to br3 if that makes sense?
obviously i understand in real life i can just fill it with weld it just seems quite a way out to me
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Slimy38
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| posted on 23/10/16 at 06:12 PM |
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quote:
Originally posted by subjated
the Br5,6,11 and 12 "square" measures correct but when i join Br3 and 4 to br11 the overall dimension where br3 and 4 would meet br10 ends
up at 918mm
so br10 end up "halfway" (its actually about a quater) inside br4 when i join br10 to br3 if that makes sense?
obviously i understand in real life i can just fill it with weld it just seems quite a way out to me
I don't get how you can have two ends of a parallelogram in the wrong place? How are you so sure BR3 and BR4 are in the right place and at the
correct angle? Which measurements have you used?
If you put BR10 in the right place and put BR3 and BR4 on to it, what measurement is wrong?
I have the book errors as PDF's somewhere, PM me an email address and I can ping them over. However, I will say there are no errors in any of
the BR pieces. The front frame construction on page 37 is the first real step away from the book, and that's only to make the suspension mounts
sit better.
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subjated
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| posted on 23/10/16 at 09:00 PM |
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quote:
Originally posted by Slimy38
quote:
Originally posted by subjated
If you put BR10 in the right place and put BR3 and BR4 on to it, what measurement is wrong?
I have the book errors as PDF's somewhere, PM me an email address and I can ping them over. However, I will say there are no errors in any of
the BR pieces. The front frame construction on page 37 is the first real step away from the book, and that's only to make the suspension mounts
sit better.
PM sent
ive done it the other way so br3/4 is on br11 if i join it the other way an put br3/4 on br10 i get the correct 924mm but then br3/4 sit nearly 10mm
longer than br11
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nick205
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| posted on 24/10/16 at 08:14 AM |
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As suggested, make the chassis and measure/make the tubes to fit. From personal experience CAD (3D included) is very useful, but it is a screen
representation of reality. What appears right/wrong on screen is often best corrected in reality.
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jps
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| posted on 24/10/16 at 09:54 AM |
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Or....
quote:
Originally posted by subjated
obviously i understand in real life i can just cut the pieces of metal to actually fit the gap
!!! :-)
[Edited on 24/10/16 by jps]
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Dean m
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| posted on 24/10/16 at 02:08 PM |
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Hi.
If there is any measurements or help I can provide just ask as I have my bare chassis on the build table at the minute.
I used a Talon flat pack chassis kit so it all goes together like a 3d jigsaw ( you almost don't need the book )
Can I ask are the measurements correct when you measure from br12 to br11 813mm outside edge to outside edge and br12 to br10 1385mm outside edge to
outside edge?
I drew the bottom rails out on my build board before laying down any metal and the measurements where all spot on.
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subjated
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| posted on 24/10/16 at 06:31 PM |
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thanks for all the replies, im using a 3d cad package to be precise.
in answer to your question dean (thanks for the help of measurements too!), yes those measurements are correct, its just as though the angles of br3/4
are wrong
talon suggests that i "put the computer away and go lay out tube on a build table" but talon himself sells flat pack kits; and if they go
together as well as everyone says i can only assume hes made tweaks along the line.
i shall be cutting my tube at work and welding at home, but if i cut the tube exactly to the book appendix i know for certain it wont fit without some
"modification"
i know full well i can get around this, and im not particularly concerned, just curious as to why it doesn't seem go together properly in a 3d
model since the book states "the measurements in this book are very precise"
if it is my mistake somewhere at least i wont scrap a bit of tube cutting it to what ive drawn and further down the line i can use the model to check
seat fitment (which i plan to fabricate from aluminium sheet) stress tests etc etc has all sorts of useful applications!
plus i can start building yet so this is as close as i can get
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Slimy38
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| posted on 24/10/16 at 10:21 PM |
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quote:
Originally posted by subjated
quote:
Originally posted by Slimy38
quote:
Originally posted by subjated
If you put BR10 in the right place and put BR3 and BR4 on to it, what measurement is wrong?
I have the book errors as PDF's somewhere, PM me an email address and I can ping them over. However, I will say there are no errors in any of
the BR pieces. The front frame construction on page 37 is the first real step away from the book, and that's only to make the suspension mounts
sit better.
PM sent
ive done it the other way so br3/4 is on br11 if i join it the other way an put br3/4 on br10 i get the correct 924mm but then br3/4 sit nearly 10mm
longer than br11
Info sent, send me both CAD pics and I'll see if I can tie it in with my chassis.
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Slimy38
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| posted on 24/10/16 at 10:31 PM |
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I've just realised something. Are you using the profile angles to determine where the tube should lie? If so, that's where the error is.
The profiles are to the nearest degree which is about as accurate as a human can cut, and plenty accurate enough to make a weldable joint. But
they're nowhere near accurate enough for a CAD program. That would account for the missing distances.
Try and lay things out by the lengths and positions only, let the angles sort themselves out. Use the diagonal measurements to double check, they
should be spot on too.
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subjated
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| posted on 25/10/16 at 07:33 PM |
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quote:
Originally posted by Slimy38
I've just realised something. Are you using the profile angles to determine where the tube should lie? If so, that's where the error is.
The profiles are to the nearest degree which is about as accurate as a human can cut, and plenty accurate enough to make a weldable joint. But
they're nowhere near accurate enough for a CAD program. That would account for the missing distances.
Try and lay things out by the lengths and positions only, let the angles sort themselves out. Use the diagonal measurements to double check, they
should be spot on too.
This is as i may have suspected, that answers my question, i could laser cut my tube with a +/- 0.1 degree accuracy which is why i asked, but since
the measurements are not accurate enough for that ill set about the old fashioned way!
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Slimy38
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| posted on 25/10/16 at 08:56 PM |
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quote:
Originally posted by subjated
This is as i may have suspected, that answers my question, i could laser cut my tube with a +/- 0.1 degree accuracy which is why i asked, but since
the measurements are not accurate enough for that ill set about the old fashioned way!
Yeah, I'm not sure Chris Gibbs had laser cutting in mind when he wrote his book!  Glad to hear you're all sorted though.
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subjated
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| posted on 26/10/16 at 06:17 PM |
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quote:
Originally posted by Slimy38
Yeah, I'm not sure Chris Gibbs had laser cutting in mind when he wrote his book!
a very valid point, should of thought of that!
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