Rear axle line - sanity check please

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ChrisS
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Rear axle line - sanity check please

Post by ChrisS » 16 Apr 2015, 02:21

Hi folks,

My head is now very full of answers and questions, but so far, not too many line up.

So, could I ask someone to confirm or deny the following for me please?

Rear axle line means where the centre of the rear hub ends up.

If I extend the engine bay rearwards by adding to the distance between 300 and 307, I relocate the rear axle line back and the suspension points back the same amount using the jig, referenced off the rear axle line in it's new location.


And answer this question:

The result of the above is simply to extend the wheelbase - I do not re-jig the wishbones to keep the uprights on the original axle line.

Thanks in advance.

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freakynami
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Re: Rear axle line - sanity check please

Post by freakynami » 16 Apr 2015, 02:41

ChrisS wrote:Rear axle line means where the centre of the rear hub ends up.
Yes.
viewtopic.php?f=14&t=514#p4965
ChrisS wrote:If I extend the engine bay rearwards by adding to the distance between 300 and 307, I relocate the rear axle line back and the suspension points back the same amount using the jig, referenced off the rear axle line in it's new location.
Yes to this too :)
ChrisS wrote:The result of the above is simply to extend the wheelbase - I do not re-jig the wishbones to keep the uprights on the original axle line.
Correct - move all of the pickup points, and suspension arms to follow the new location of the hubs and it'll match the intended geometry.
There is of course more to this, but I'll let Kurt confirm or deny this: you "may" be able to leave the forward end of the trailing link in the same place, and lengthen just that suspension arm. This "may" not affect geometry adversely, and will keep the suspension pickup near a chassis node for strength.

Also don't forget to get a fine red pen, and go through the errata thread (viewtopic.php?f=24&t=490&start=0), and mark-up your book with the few small revisions that have been discovered along the way.

ChrisS
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Re: Rear axle line - sanity check please

Post by ChrisS » 16 Apr 2015, 03:52

You Sir, are a star, thank you.

I did search out that thread you quote...but missed the critical line from Kurt :oops:

My book is plastered with Post-It notes now!! Mostly notes of my own but I have marked up the one or two significant bugs that are published. Just need to make sure I mark up the 150% scale copies I made of the drawings...

I did wonder about the trailing link, but one potential advantage of moving the pickup point back that struck me - it would probably allow for landing 309L & R bang on the intersection of 300/303/main hoop. Not a big deal, but nice to make use of the option is possible I guess.

Comforting to know I haven't got it totally round my neck (yet!).

Cheers.

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Re: Rear axle line - sanity check please

Post by Midlana1 » 16 Apr 2015, 07:32

Lengthening the trailing link is a good thing for wheel geometry because it doesn't pull the hub as forward in bump and droop. BUT, the toe link is setup to correct for that when using the original length arm, so with the longer link, toe control will be very slightly different. The reality is that you'll probably won't notice. Probably.

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Re: Rear axle line - sanity check please

Post by ChrisS » 16 Apr 2015, 07:54

Thanks Kurt - I'll see how much I have to extend the engine bay first, then review it before making a final decision about that link & pickup point.

If it's subtle, then it's almost certain I won't notice it, but I can always mock it up once the rest of the brackets are in place, and quantify it, then decide which option I prefer.

Tad more wheelbase won't hurt for what I want from the car either.

Thanks chaps.

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Re: Rear axle line - sanity check please

Post by Midlana1 » 16 Apr 2015, 13:11

It'll also move the CG forward some.

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Re: Rear axle line - sanity check please

Post by ChrisS » 17 Apr 2015, 01:19

Ah, of course, I hadn't considered that. That's another small benefit isn't it.

I'm hoping I won't have to make too big of a change, but the engine bay on my Stratos copy was very snug and I'd rather avoid that if I can. At least I now know for sure that extending it is not something to be too worried about.

Due to pick up the donor on Sunday - 'll post up a picture assuming all goes to plan.

Thanks again chaps, appreciate the input.

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