hillbillyracer
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| posted on 26/10/06 at 10:41 PM |
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DIY front uprights
It could be that I'm missing something but just about every seven type car I've looked at doesnt have good front upright goemetry. The
king pin inclination angle seems to be either a long way from vetical (Sierra) or miss the centre line of the tyre by a mile (Cortina). How much does
this compromise the handling?
Has anybody made their own uprights?
I've seen some on here by Stuart Taylor but they look a bit light for a car engined car & I dont want to use rose joints as mine will be a
road car.
I thought about using the stub axles, hubs & discs from the back of a large fwd car, if it can hold the back of a fat saloon in place surely it
could handle the front of a seven?
Another point is what are the effects of using a bottom balljoint not designed to carry the weight of a car?
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nick205
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| posted on 27/10/06 at 07:40 AM |
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IMHO it comes down to cost and availability. Most things are a compromise somewhere along the line and using readily available front uprights with
minimal modification is very cheap and simple if you accept that the compromise is imperfect, but adequate geometry.
IIRC Dax supply fabricated front uprights for the Rush, but I know they won't be cheap. I would hope/assume that what you're paying for
is significantly improved geometry in a tested product.
Most kit and locost cars use Maxi or Cortina lower ball joints, which were designed to carry the weight of heavier cars for greater mileages, so I
don't see that as an issue. However the commonly used Transit drag link used for the top ball joint doesn't overly fill me with
confidence, but having said that you don't seem to hear of any failures related to this part.
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hillbillyracer
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| posted on 27/10/06 at 07:59 AM |
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Talked to the Dax guy at Donnington about those uprights, once he worked out I didnt want to buy his kit he lost intrest very quickly.
I may give it a go as I have a decent workshop & more skill than money (that said, I'm skint!).
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nick205
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| posted on 27/10/06 at 08:52 AM |
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Be interested to see what you make - keep us posted!
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andyd
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| posted on 27/10/06 at 09:28 AM |
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I'm in the process of designing my own uprights. I'm going with CNC'd ally billet for the uprights, steel stub axles and steering
arms plus ally hubs.
My intention is to design the whole setup based around the MK2 Escort steering rack length and get the optimum setup. Whether I'll be able to
achieve this of course remains to be seen! 
Andy
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Ivan
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| posted on 27/10/06 at 11:34 AM |
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I think Rorty was going to design do-it yourself uprights of improved geometry made of interlocking plates but I have not been able to find any final
design - does anybody know if they were done.
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big_wasa
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| posted on 27/10/06 at 04:43 PM |
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No measurements but here is the pic
[img]http://www.locostbuilders.co.uk/viewthread.php?action=attachment&tid=33544&pid=275013[/img]
Taken from this link
I dont know if Mnr have finished them? I havnt heard...
[Edited on 27/10/06 by big_wasa]
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peterriley2
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| posted on 27/10/06 at 04:51 PM |
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rorty started planning a new front end which uses vw golf parts- readily available and strong, he said he would design a whole front end for better
handling purposes, but would need the info shown in red here. ive been trying to
find the info but have got nowhere- i think it means buying each part and either dimensioning them yourself, or sending them to him. if anyone can
help, rorty and I (and i guess a lot of others on here) would greatly like the info!!
Joel
If you dont respect yourself, dont expect respect from anyone else
Live your dreams, dont dream your life
Women only want you for one thing- everything!
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cymtriks
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| posted on 27/10/06 at 07:59 PM |
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Most modern double wishbone set ups go for a small or zero scrub radius and a high KPI of around 12 degrees or more.
For example the original Elise has a scrub radius of 10.5mm and a KPI of 12 degrees.
If you draw out a wheel containg a caliper and brake disc and then allow for a bit of clearence to the bottom hub joint and then select a small scrub
radius you won't get any smaller with the KPI.
Older wishbone suspensions had much lower KPI, circa 7 to 9 degrees, but they had huge scrub radii.
Now I know that many older cars handled OK but in most cases modern cars are way better and, perhaps more importantly, modern tyres are made for
modern suspensions.
Check out the uprights on the Meerkat front. Alan uses a simple mod to the uprights on a McPherson strut hub to turn it into a double wisbine hub.
Judging by the number of upright threads that mod could be saleable.
There are also other hubs that could be used including-
Elise
MGF
S2000
RX8
MX5 / Miata
Corvette
All of these uprights have the advantaqe of comming ready made with a range of OEM parts that will fit straight on.
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hillbillyracer
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| posted on 28/10/06 at 07:46 AM |
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Thanks for the Info on KPI & scrub radius Cymtriks. If I use a modern sliding caliper it should give me more clearance & be easier to reduce
the scrub radius than the old two pot Cortina ones.
The donors you suggest are worth a look but will not be in my local scrappy & could be expensive.
I was mabye going to use somthing like VW Passat rear stubs & hubs, VWs used to have a stub axle that bolted on with 4 10mm bolts. This would give
me a 100mm PCD meaning plenty of choice in discs & wheels.
Of course I would then be looking for a diff & hub set up for the back with a 100mm PCD. E30 BMW, any others?
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Syd Bridge
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| posted on 28/10/06 at 10:08 AM |
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It's much easier to get the dimensions near correct using a modern Sierra or fwd upright.
With the axle rotating, and not a hub on an axle, everything can move out and helps get rid of scrub. Big kpi numbers really are not necessary, if you
take some care with the geometry in the first place.
Cheers,
Syd. 
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Bob C
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| posted on 28/10/06 at 11:13 AM |
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I used mx5 uprights in my build - these are not totally straightforward to use - there is a crazy angle on the TRE's and the stock arrangement
puts therack IN the bottom wishbone. . . All fairly easily surmountable but not just bolt- together like a cortina system.
Having zero scrub and not too much KPI means that the front of the car is not lifted up when lock is applied resulting in poor self centring at low
speed (ie the SVA test) With the book error corrected and 5.5degrees castor too! I have a feeling that with the low weight of the car (210kg on front
axle) I'd need more like 7 degrees of caster. For now I'm hoping that the toe- out trick & high tyre pressures will get me through but
I don't understand why toe- out helps - we'll see.
Bob
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JoelP
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| posted on 28/10/06 at 02:46 PM |
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i think toe out causes self centering via the ackerman angles. With the wheels both say 5 degrees out you have a certain amount of drag as the tyres
have to slip. If one was straight, the other wheel might be pointed 10.5 degrees out, due to ackerman, hence overall more resistance to motion.
However, im not sure how this actually makes the wheel want to point forwards. Maybe it just serves to amplify the existing trail/castor effect.
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hillbillyracer
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| posted on 29/10/06 at 08:36 AM |
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I thought the thing that contributed to self centreing most was the "shopping trolley effect" from the caster angle.
Thinking about it I could use a Mondeo stub, just cut it out of the susp arm & tidy it up in the lathe. This would leave me back on the Ford PCD
& I could use the Sierra backend I already have.
The problem with using a rotating stub from a Fwd car is I'd then be fabricating around a bearing housing with the liklyhood the welding would
distort it. A mate building a hillclimber had this trouble, but has managed it.
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NS Dev
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| posted on 29/10/06 at 08:51 PM |
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turn the housing out on the lathe after welding, m/c it small, weld it then skim it out. Done it a few times and as ong as you get the housing a
reasonable thickness (ended up with between 8 and 10mm across the housing) it works fine.
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ZEN
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| posted on 29/10/06 at 09:20 PM |
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Luso motors are selling ali uprights http://www.lusomotors.com/product_1.html but aren't
DIY.
My YouTube channel Cars, bikes - track days, motorsport, sim racing and more.
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hillbillyracer
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| posted on 29/10/06 at 10:10 PM |
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I could indeed use my lathe to make the bearing housing under size & true it up when the welding is done, but its 14 years since I did any
precision work on a lathe & that was just in the 1st year at technical college. I think I'd best have some practice first!
This is all just thinking so far, it will be a month or two before I get into the workshop on this one.
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scotmac
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| posted on 30/10/06 at 06:24 PM |
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quote:
Originally posted by ZEN
Luso motors are selling ali uprights http://www.lusomotors.com/product_1.html but aren't
DIY.
I tried to get some uprights from Luso about a 9 mos ago. Had a bit of an email discussion, but it went nowhere. ie, i don't think he is really
in production.
Has anyone been able to get a product out of him?
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scotmac
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| posted on 3/11/06 at 04:24 PM |
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Yep....that's what i thought.
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