dern
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| posted on 10/6/07 at 08:17 PM |
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Front suspension sanity check (how many threads is enough?)
Spent this afternoon tacking in the top suspension mounts using a jig inspired by some I've seen on here. Pretty please with the results but I
have a couple of questions...
In order to get zero camber (I want to run slicks at some point) I had to wind out the top transit drag link and the top rose joints a fair bit. At
zero camber both rose joints are in by 5 whole threads which is 10mm in to the wishbone of the full 30mm available. Also the transit drag link is also
only 5 whole threads in to the top bush of the wishbone. I can't move the lower wishbone in any further and in order to get the current state of
play I've had to wind the lower rose joints in so far I'm going to have to find some half nuts to use as locking nuts. Basically is this
state of play safe? If not can I get some longer rose joints so I can wind them in some more, wind the transit link in more and basically shift the
wishbone out a bit if you see what I mean? The rose joints are M10s.
Secondly, suspension travel... I have tons of movement upwards in the arrangement but it only moves down 3" (from the lower wishbone being
horizontal) until the assembly binds. The thing binding is the lower balljoint. I imagine this is plenty but just wanted to check.
The lower shock mount seems a long way out and with the top one fitted under the top rail the shock will be at quite an angle. Is this normal?
The wishbones are supplied by ace sportscars by the way.
Here's some pictures so you can see the arrangement I've got...
Thanks for any advice.
Regards,
Mark
[Edited on 10/6/07 by dern]
R1 (2003 FI) powered Locost in progress
Fireblade/Impreza
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nitram38
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| posted on 10/6/07 at 08:24 PM |
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I wouldn't like to drive your car!
I personally would not use M10 rod ends and if I did they would be wound most of the way in.
I use 1/2" unf on my projects and I have not had a failure.
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JoelP
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| posted on 10/6/07 at 08:35 PM |
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3" droop is adequate, you can set the spring to prevent the balljoint binding.
How much further in would the top link be if you had 2 degrees of camber? Not muhc id guess. With this in mind, id remake the top bones maybe 20mm
longer - doesnt seem right to me having them that far out.
Also, 10mm roses seems more suited to trackwork, i cant see the benefit on the road of making them that small. My trackcar has 10mm roses, so that i
can use a mix of 3/4" and 7/8" tubing.
Martin, whats the narrower dimension of your oval tubes?
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ecosse
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| posted on 10/6/07 at 08:41 PM |
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I would worry about the top BJ/TRE being so far out, and as said M10 for the rod ends may be a bit on the small side, I asked this question myself a
while back and the consensus seemed to be 1/2 for road use.
And you could fit the top shock mounts on the outside of the chassis to steepen the angle up a bit
Cheers
Alex
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jambojeef
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| posted on 10/6/07 at 08:45 PM |
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Looking at your setup there is nothing unconventional.
Even if your shock is slanting at say 45 degrees - you are still getting around 70% of the upward motion of the wheel transferred to the shock,
depending on what the car is for, you may not notice this compared to a slightly more upright shock.
In terms of suspension movement - you are right in thinking that 3" in droop is plenty for 7s.
You would be well advised to source some different rod ends with longer shanks though. I think the rule of thumb is 1.5 x the diameter of the fixing
needs to be threading into the wishbone or fixing.
You might want to double check the quality of the rod ends themselves too - Nick Skidmore on here sells goldline rod ends which would be more than up
to the job in question as M10s but a check to their static UTS would be well worth it.
Geoff
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dern
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| posted on 10/6/07 at 08:46 PM |
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quote:
Originally posted by nitram38
I wouldn't like to drive your car!
Very encouraging.
The 10mm rose joints were supplied with the wishbones. Apart from the fact that you use 1/2" and wouldn't personally feel happy with 10mm
rose joints is there any engineering reason why they aren't strong enough? If so I'm surprised that they were supplied but I can always
drill and tap the bones out to take bigger rose joints.
Is there any alternative to making up new top bones? I can do it but it seems a waste to chuck the ones I've bought. Can these be extended in
any way?
Thanks,
Mark
PS. The car will be predominantly for track use and some sprinting. I'm not that bothered about driving it on the road.
[Edited on 10/6/07 by dern]
R1 (2003 FI) powered Locost in progress
Fireblade/Impreza
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ReMan
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| posted on 10/6/07 at 08:53 PM |
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Couuld you not raise the mounting point of the upper wishbone mount sligtly?
Or make a bigger mounting bracket?
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blakep82
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| posted on 10/6/07 at 08:53 PM |
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i also would only use 1/2" minimum rose joints. In fact, all the rose joints on my car are 5/8", but thats beside the point. I've
been told and recommended to use 1/2" minimum. that was for racing use though, so 10mm should be alright. I always prefer to over do things
though.
I'd also like to see the top ball joints screwed in more. I'm surprised the the wishbones would be supplied so short.
________________________
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blakep82
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| posted on 10/6/07 at 08:56 PM |
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quote:
Originally posted by dern
PS. The car will be predominantly for track use and some sprinting. I'm not that bothered about driving it on the road.
[Edited on 10/6/07 by dern]
remember the stresses on raci e suspension are a lot higher than road cars. I remember a racing driver tell me the stresses on road suspension is only
something like 30-40% of that on a race car.
________________________
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JoelP
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| posted on 10/6/07 at 08:57 PM |
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are you sure they arent sierra upper bones?
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JoelP
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| posted on 10/6/07 at 08:59 PM |
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quote:
Originally posted by blakep82
quote:
Originally posted by dern
PS. The car will be predominantly for track use and some sprinting. I'm not that bothered about driving it on the road.
[Edited on 10/6/07 by dern]
remember the stresses on raci e suspension are a lot higher than road cars. I remember a racing driver tell me the stresses on road suspension is only
something like 30-40% of that on a race car.
My thinking is that, on a road car, failure is unacceptable. On a track car, you try to push the envelope to improve it. Ie lighter/thiner bones etc.
I believe chapman used to weaken stuff til it broke than back up a few gauges/grams.
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blakep82
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| posted on 10/6/07 at 09:00 PM |
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^ also, not sure it would make a whole lot of difference (it maight make enough though) seems you have the wrong side upright on there. you seem to
have the left side one on the right
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blakep82
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| posted on 10/6/07 at 09:01 PM |
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quote:
Originally posted by JoelP
quote:
Originally posted by blakep82
quote:
Originally posted by dern
PS. The car will be predominantly for track use and some sprinting. I'm not that bothered about driving it on the road.
[Edited on 10/6/07 by dern]
remember the stresses on raci e suspension are a lot higher than road cars. I remember a racing driver tell me the stresses on road suspension is only
something like 30-40% of that on a race car.
My thinking is that, on a road car, failure is unacceptable. On a track car, you try to push the envelope to improve it. Ie lighter/thiner bones etc.
I believe chapman used to weaken stuff til it broke than back up a few gauges/grams.
he could probably also afford to build a new car if he wrecked one 
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don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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dern
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| posted on 10/6/07 at 09:01 PM |
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quote:
Originally posted by blakep82
i also would only use 1/2" minimum rose joints. In fact, all the rose joints on my car are 5/8", but thats beside the point. I've
been told and recommended to use 1/2" minimum. that was for racing use though, so 10mm should be alright. I always prefer to over do things
though.
I understand what you're saying (and the other posters). It's just that I've got 8 on the front and 10 on the back
for my dedion setup and with the cost of the taps too it represents a significant cost to change. It's not that I'm doubting
anyone's good intentions... honestly 
Regards,
Mark
R1 (2003 FI) powered Locost in progress
Fireblade/Impreza
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JoelP
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| posted on 10/6/07 at 09:01 PM |
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lol, true
cross posting, we're going too fast! That was to blake.
Mark, i wouldnt worry myself. Just dont overtighten the lock nut! Thats more likely to cause a failure than anything else.
[Edited on 10/6/07 by JoelP]
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dern
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| posted on 10/6/07 at 09:06 PM |
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quote:
Originally posted by blakep82
^ also, not sure it would make a whole lot of difference (it maight make enough though) seems you have the wrong side upright on there. you seem to
have the left side one on the right
Really? How can you tell?
I tried both and the other one makes the state of affairs worse.
Regards,
Mark
R1 (2003 FI) powered Locost in progress
Fireblade/Impreza
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gottabedone
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| posted on 10/6/07 at 09:13 PM |
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Mark,
How much movement would you gain by making new chassis brackets for the wishbones?
You could move the bolt holes outwards (horizontally) maybe 5-7mm, keeping your geometry correct but allowing you to wind your rose joint 5-7mm
further into your top bone.
may be a lot less work and a lot cheaper.
good luck
Steve
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JoelP
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| posted on 10/6/07 at 09:16 PM |
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quote:
Originally posted by dern
Really? How can you tell?
I tried both and the other one makes the state of affairs worse.
Regards,
Mark
Unless im mistaken, blake's correct. Cortina is a front steer hub, ie the steering arm should point forwards. Doesnt HAVE to be, but you would
affect steering geometry if you swapped them.
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dern
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| posted on 10/6/07 at 09:18 PM |
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quote:
Originally posted by JoelPUnless im mistaken, blake's correct. Cortina is a front steer hub, ie the steering arm should point
forwards. Doesnt HAVE to be, but you would affect steering geometry if you swapped them.
Ah, opps. So should I simply turn this one over or
use the other one? One of the balljoint holes in the hub is further in board than the other. Should this be at the top or the bottom?
Regards,
Mark
R1 (2003 FI) powered Locost in progress
Fireblade/Impreza
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Avoneer
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| posted on 10/6/07 at 09:30 PM |
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Simple answer - top bones are too short and I wouldn't consider them to be safe enough.
I'd be happy with 10mm rose joints if they were good quality and screwed nearly all the way in and the track rod end definately need to go in a
lot more.
I think the easiest and cheapest solution would be to get some new top bones made.
Volvorsport (off here) made some very similar ones to my spec and did a fine job.
http://locostbuilders.co.uk/viewthread.php?tid=35371
Pat...
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dern
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| posted on 10/6/07 at 09:30 PM |
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quote:
How much movement would you gain by making new chassis brackets for the wishbones?
You could move the bolt holes outwards (horizontally) maybe 5-7mm, keeping your geometry correct but allowing you to wind your rose joint 5-7mm
further into your top bone.
may be a lot less work and a lot cheaper.
It's a good idea. Thanks to ReMan for suggesting it earlier too).
The thing that makes me most unhappy about doing that (and with the situation as it stands) is that all this takes out all the adjustability that
I've built in by choosing the rosejoints in the first place.
To be honest as I haven't had a resounding "that's be fine" response I'm going to address the problem though.
I'm leaning towards the idea of making a new pair of top wishbones and sticking with these rosejoints. It won't be expensive, just time
consuming but I've got plenty of that at the moment. If I subsequently read more information suggesting the rod ends aren't string then I
can always tap all the bones and fit 1/2" rod ends then. Anyone got any plans for top bones that don't require any bending?
Thanks for all the information.
Regards,
Mark
R1 (2003 FI) powered Locost in progress
Fireblade/Impreza
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Avoneer
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| posted on 10/6/07 at 09:31 PM |
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Oops, typed to slow - but you get the same conclusion.
Pat...
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blakep82
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| posted on 10/6/07 at 09:42 PM |
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stepping back a bit, the further inboard of the 2 ball joint holes should be at the top. and yes, cortina's steer from the front. so the
steering arm should be at the front also. i gather you haven't started on steering rack mounts yet, as this could cause a whole lot of confusion
later
________________________
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don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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ReMan
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| posted on 10/6/07 at 09:43 PM |
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No bends in my top bones. These are GTS (Yes GTS and well made too ) items, but theres no rocket science in the design..........
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nitram38
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| posted on 10/6/07 at 09:45 PM |
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My eliptical bones are 40mm X 16.7mm X 2mm, bought from Ralt racing.
10mm rod ends are ok for a single seater but a car that can carry two people, I would not go under 1/2".
I am not sure but I think the sprintR has 5/8".
Rod ends at full extension create more of a leverage point on the threads and a thread is a natural cut into the material to help with causing a
break. The material that is taking the load is actually only about 8mm when you take off the thread thickness.
Remake your top bones if they are too short. I re-made mine to give more castor and it didn't take long.
I also remade my cast uprights in steel as originally they were made in aluminium, because on the finished car, they looked too weak. That mistake
cost me another £400!
To remake your bones, you are only talking about £20-30?
There is hardly any weight saved by using 10mm over 1/2", only more of a risk of failure.
Go with 10mm if you must, but wind them in.
My other advice is that your camber should be about 0.5 to 1 degree.
It does make your tyres wear, but it also helps with grip in corners.
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