James
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 posted on 15/5/02 at 04:12 PM |
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Rails J1&J2, FU1&FU2
Could some clever person, or someone with CAD (or both!) please tell me 'The Book' distance between J1&J2 at the point where they join FU2&FU1
please?
Also, could someone tell me the angle at which FU1&FU2 sit off vertical please.
Thanks,
James
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interestedparty
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| posted on 15/5/02 at 05:12 PM |
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Try downloading the 'book' chassis from Jim McSorley's site, you should get your answers from the drawings in PDF format.
http://www.mcsorley.net/locost
John
As some day it may happen that a victim must be found,
I've got a little list-- I've got a little list
Of society offenders who might well be underground,
And who never would be missed-- who never would be missed!
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Dunc
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| posted on 15/5/02 at 05:17 PM |
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James check out my pic in the photo section. Is this what you're after?
PS. the top of FU also joins onto S & T and not just on J for extra strength. The bottom of FU should also be in line with E.
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jbmcsorley
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| posted on 15/5/02 at 07:46 PM |
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I found FU1/2 to sit at 70.8 degrees from the horizontal in the book design. The exact distance between the tops of FU1/2 is something I'll have to
look up in CAD.
However... the distance between J1 and J2 as compared to the distance between FU1/2 on a completed build are not necessarily the same thing. It has
been discussed in great detail on other list groups that the FU1/2 tubes actually reside about .22" inside the outer face of J1/2 on the finished
build in order to get near perfect alignment of the upper wishbone mounts.
You can actually see this in 'the book' if you look very closely at the front view detail of the suspension mounting layout (don't have the page
number with me). If you follow FU1 in the drawing to where it meets J1 (behind LA), you can actually see that Ron drew FU1 a little inboard of J1.
This is something not mentioned in the assembly instructions.
This is also something I have confirmed in CAD as well... FU1/2 should not be fully welded flush with J1/2... you'll be cursing Ron when you have to
cut FU1/2 back out again to get the suspension to line up ("FU"1-2... aptly named me thinks) 
So, would you like the exact measure between J1/2... or the exact measure between FU1/2 on a build where FU1/2 allows for upper wishbone mounting
alignment? Also, would you like that measure in a plane that agrees with the front of FU1/2, or at the rear... J1/2 sits at an angle of course, so
the width is different depending on front or back. What are you shooting for anyway?
If it were my build, I would increase the width of the L assembly (LC and LD) by about .2" to each side so that FU1/2 could sit nearly flush with the
outside edge of J1/2... I'm surprised Ron didn't choose that approach, but I guess he wanted to maintain full standard measures on LA/LC.
However, if you're interested in these numbers to help you layout a custom design, you might consider what I found to be a more valuable measure (or
constraint) when laying out the front end: The width of the back of the book nosecone at a known distance from the front end.
So here we go... The book nosecone design is 26" wide at a distance of 12" from the front of LC (the back of the nosecone). I think my CAD drawings
show this as 25.8"... which is nearly perfect given the thickness of the 16 guage ally (.065") brings the overall width of the assembled chassis
extremely close to 26". This is all CAD of course... any fiberglass guy that can work up exactly 26" should be working in aerospace, not
locost-space.
Anyway, what I found to be a valuable measure was the 26" spread at 12" back... that way, the angle (from a top view) of J1/2 can be something other
than 10 degrees (the book measure) and you can widen the rear end as you see fit while retaining a book nosecone fit. The engine bay can get longer
as well... making for a very flexible design.
I'm babbling at this point (rather bored at work)... So, why did you need this measure anyway? 
-Jim M.
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Dunc
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| posted on 15/5/02 at 08:00 PM |
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Jims right, FU sits in slightly inboard of the J tubes. A jig with the mounting positions of the upper brackets would suit your cause. If you use it
to set FU and LA LB in position the two brackets should line up.
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David Jenkins
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| posted on 16/5/02 at 07:31 AM |
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Don't forget the important bit, found out by many folks (including me) - just tack weld the FU's in place until you set up the front suspension
brackets.
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Big John
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| posted on 17/5/02 at 12:09 AM |
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"The book nosecone design is 26" wide"
Jim- I thought you said the standard nosecone was 24" across the back? What's does the one you got from CMC measure?
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James
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 posted on 17/5/02 at 05:03 PM |
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Thanks for all the replies everyone- really helpful.
I forgot to ask at the same time: could you tell me the angle of LA/LB please?
quote:
I'm babbling at this point (rather bored at work)... So, why did you need this measure anyway?
-Jim M.
Erm... well, I thought I'd be clever and mess around with my chassis dimensions (width, length etc.) largely to suit the Sierra track but also for my
benefit as I'm 6'2" and plan to do some long journeys in the finished car so wanted a bit more room.
What I managed to avoid doing when deciding to do this was realise that doing so is potentially really gonna mess with the front suspension setup.
I've now welded up enough of the chassis that I don't want to start again and as I'm now doing the nosecone I want to make sure the end result
actually 'works'.
Basically I've learnt that I shouldn't have been lazy and should have learnt how to use CAD! Would have been much easier in the long run!
Thanks again,
James
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jbmcsorley
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| posted on 21/5/02 at 09:32 PM |
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Is that "Big John" Greenwood?
I have to apologize for mis-stating that the book nosecone was 24" at the back... if that's still published somewhere, let me know so I can change
it.
The Champion Motor Cars (out of Alabama, USA) nosecones come in two flavours...
The book: 26" wide at the rear, a distance of 12" from the front. 7.5" off the top of the chassis, 10" below the top of the chassis in the front
(requiring a cow catcher to fill the 3" gap).
The 'newer' design: 24.25" at the rear, a distance of 10.5" from the front. 8.5" above the chassis at the rear, 13" below the top of the
chassis at the front (no gap with book build).
I have the newer design in my garage, so I'm dead sure of the measures. The book design measurements were provided to me by the folks at CMC and I
confirmed that both designs fit my CAD model dead on.
While the two nosecones are different widths, they are also different depths.... so they share the same taper on the sides. Both will also fit the
442 drawings on my website, although I would recommend the 'newer' design as the cowcatcher needed for the original book nose would be 5" tall and
look aweful.
Cheers,
-Jim M.
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jbmcsorley
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| posted on 21/5/02 at 09:36 PM |
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Hi James,
Seeing as how your reason for asking about the distance between J1/2 at FU1/2 is based on an interest to customize the chassis... I highly recommend
that you use the back of the nosecone as your constraining dimension. FU1/2 will probably shift inward or outward depending on where J1/2 ends up
due to moving E forward.
Oh, and the angles on the front of LC/LD are 116.6 degrees from horizontal... you can read that in my CAD drawings of the book design as well.
Cheers,
Jim M.
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James
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| posted on 22/5/02 at 10:10 AM |
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quote:
Hi James,
Oh, and the angles on the front of LC/LD are 116.6 degrees from horizontal... you can read that in my CAD drawings of the book design as well.
Cheers,
Jim M.
Hi Jim,
Thanks for the advice. I actually got this figure myself last night using Trig' but it's nice to have had it confirmed!
Although I had 117° so guess I had a bit of rounding error... :-)
Thanks,
James
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jbmcsorley
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| posted on 22/5/02 at 02:25 PM |
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Cheers James,
Let me know if there are any other measures I can help with.
Here's a summary of how I handle customizing the front end (with CAD of course, but the same principles can be sketched if you're really
patient)...
1) fix the point on J1/2 where it will meet the back of the nosecone. This is typically 26" wide at a distance of 12" from the front of L. I
actually inserted a hidden tube in my model and called it the "nosecone spacer"... just to help control the geometry.
2) Move the L assembly fore and aft to fit your needs. E should sit away from L the same amount as the book. The "nosecone spacer" will move fore
and aft along with the L assembly due to the 12" contraint. The length of E and the width of L are not fully determined yet... so they can be
whatever for now. The taper on J1/2 will be shifting as you move the L assembly fore/aft... That's perfectly Ok as long as the 26" measure is
maintained and J1/2 still meets the ends of the dashboard.
3) "Install" FU1/2 on J1/2 at the angle provided by the book and coplaner with E, but not necessarily agreeing with the width of E quite yet.
4) Now change the width of E until it agrees with the outer edge of FU1/2. What's interesting here is that we have the opportunity to eliminate the
whole "FU1/2 must be inset from J1/2 by about 8mm on the book chassis" issue; we have control of the width of J1/2 and E at this point in the
design... so we have the opportunity get rid of that strangeness.
5) Modify the width of LC and LD by equal amounts (to keep the angles the same as the book) until the intersection of the outer face of FU1/2 and LA/B
allows the upper bushing tubes to be concentric and parallel to the ground. This assumes you've sketched and mounted the upper brackets to know where
their bolt holes will lie.
There is only one exact point at which the brackets are fixed to their respective uprights and their holes are concentric and parallel... and this
point shifts up and down (along the outer faces) as you change the width of L. The wider the L assembly, the higher the brackets will go before their
holes line up.
You should be able to calculate a width for the L assembly that allows the brackets to agree with the book... The width of LD should be less than
the width of E by the same amount shown in the book (taking into account the 8mm offset as well). Whatever your new E width is, subtract from it the
same amount that the book does to get to LD(with an additional amount taken from each side to adjust for the 8mm anomoly). In theory your upper
brackets will be in the same spot as the book... but 8mm is not exact and it will require some tweaking. This assumes you've used _exactly_ the same
angles on FU1/2 and LA/LB in all directions.
I was able to take this whole thing a step farther by designing the L assembly taller than the book chassis while maintaining all the compound angles.
This means I can have the same bracket points as the book, but with a taller chassis.
Anyway, all of this is not easy on paper, but it is the approach I used to layout my CAD model in 3D. I can move the L assembly fore and aft, or
increase/decrease the width of the dashboard area and the whole frontend of the chassis is automatically revised; I can go through numerous
permutations in a matter of minutes and it has provided me with hours of entertainment.
Hopefully it might give you some ideas to play with.
Regards,
-Jim M.
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