Making Some Front Uprights
orton1966 - 18/12/10 at 01:23 PM
Been trying to get my head around a lot of things recently, building from scratch to my own design and whilst I originally intended to use MX5
uprights I’ve decided the low rack position gives me problems. This is mainly because I’m building a midi and the pedals are going to be right up to
front axle-line to help pull the C of G forward. So I’ve decided a high rack, single-seater style will help with clearing feet/pedals etc. Any way
long story short I think I’m going to build my own.
The basic style is similar to some I’ve seen fabricated on the road-runner sprint and other MK cars. The cad picture below shows the basic layout, be
aware this isn’t dimensioned yet because I have to decide on hubs, callipers and discs then finalise geometry.
I guess what I’m after are some thoughts on the basic design, I’m thinking 44.4mm by 2mm tube, a steering arm cut from 50mm by 25mm by 2mm box and two
plates to sandwich the lugs of the calliper. There are three turned elements the two ends threaded for either 12mm or ½” bolts for rose joints and the
axle to take a simple hub like these from a micra rear.
Equally Honda civic’s look nice but I want to get a couple of different ones to find a size/weight that works best. As usual what do people think?
[Edited on 18/12/10 by orton1966]
[Edited on 18/12/10 by orton1966]
Miks15 - 18/12/10 at 01:35 PM
Have a look at martins (nitram38) motaleira
I believe he has a high rack so whatever uprights he used might be worth looking into?
Cheers
Mikkel
russbost - 18/12/10 at 01:48 PM
Are you intending to get the axle turned up or are you intending to use a cut down "bolt in" unit? Not sure exactly what's
available.
Also it may sound obvious, but you don't want to finish up with different centre spigot diameters or different PCD for stud front & rear, it
can make buying wheels difficult!
orton1966 - 18/12/10 at 02:05 PM
I’m thinking I’ll get all the turned bits custom made, the thing I like about the micra and civic rear hubs is that they have a one-piece sealed
bearing unit so they go on a parallel axle so should be simple to make.
My thinking is that I can then use the same make front hub units to make my rears so same pcd etc.
Mal - 18/12/10 at 02:52 PM
What grade of steel are you going to use to make the axle?
austin man - 18/12/10 at 03:01 PM
why dont you contact martin at mkengineering. It seem daft to have all the turmoil of designing something which has already been sucesfully done. I
know his initial design required modifying which he dd following test drives of the vehicle. He is also using readilly available hubs as well
zilspeed - 18/12/10 at 03:49 PM
The turned top and bottom parts, I would have those turned to a step leaving a narrower shank which can then be a push fit into the main uprights.
A nice little 45 deg chamfer on both shoulders either side of the weld would allow good weld penetration and finish the job off nice.
NS Dev - 18/12/10 at 04:03 PM
Hi, I don't get the high rack centreline helping foot clearance thing?? (unless the rack on an MX5 sits behind the axle centreline?)
On the spaceframe mid engine BEC supercharged fiat 126 we're building the pedals are up to the front axle centreline (when pressed, as per Blue
Book) and there is room for a rack with Cortina uprights...............
orton1966 - 18/12/10 at 04:57 PM
quote:
Originally posted by NS Dev
Hi, I don't get the high rack centreline helping foot clearance thing?? (unless the rack on an MX5 sits behind the axle centreline?)
Some of it is a cosmetic thing, gives neater routing for the steering shaft/joints, with it being an exo car running these higher hides them up under
the cowl and gets rid of the biggest dog leg
The reason not to use MK’s is that would commit me to their choice of geometry
The turned ends do feature a very small lip to locate on the tube and a 45 weld prep, just cant see it without zooming in
Peteff - 18/12/10 at 05:15 PM
How does the ball joint fit in the top and bottom, are the holes tapered and how do you get the nut on it? If you use rear axle stubs and hubs on the
front will front brake disks fit on them? Read your threaded for joints bit now, will they need spacers turning to allow articulation?
[Edited on 18/12/10 by Peteff]
orton1966 - 18/12/10 at 06:53 PM
quote:
Originally posted by Peteff
If you use rear axle stubs and hubs on the front will front brake disks fit on them? Read your threaded for joints bit now, will they need spacers
turning to allow articulation?
[Edited on 18/12/10 by Peteff]
My thought is that i'll design the taper on the end turnings to allow full joint articulation. Brake wise i'm thinking something like
Hi-Spec 4 pots, alloy bells and 280mm solid discs (15" wheels)
[Edited on 19/12/10 by orton1966]
hughpinder - 23/12/10 at 10:34 AM
I like the idea so far. I'm not sure if this is for a road car or track. There are a few things I can only vaugely remember, and can't find
proper reference to so I'll be interested to see other peoples comments:
1. Dont forget some way to mount your mudguards/wings assuming you need them.
2. I sort of remember that fabricated uprights were not allowed on road cars, but I think it may have only been in some countries?
3. I also have a vauge memory that your feet can't pass the centre line of the front wheel - for crash protection reasons, but I think that rule
may ony be in race cars, so be carefull to allow for the position with the pedals at full travel?
4. When doing your stress calcs, remember that you may not be able to do the necessary heat treating at home to relieve the steel and get full
strength in HAZ near your welds.
Foa your midi, consider having the fuel tank and battery at the front (if you have space) to move the weight forwards.
Hope some of that's of use
Regards
Hugh
orton1966 - 23/12/10 at 04:26 PM
quote:
Originally posted by hughpinder
I like the idea so far. I'm not sure if this is for a road car or track. There are a few things I can only vaugely remember, and can't find
proper reference to so I'll be interested to see other peoples comments:
1. Dont forget some way to mount your mudguards/wings assuming you need them.
2. I sort of remember that fabricated uprights were not allowed on road cars, but I think it may have only been in some countries?
3. I also have a vauge memory that your feet can't pass the centre line of the front wheel - for crash protection reasons, but I think that rule
may ony be in race cars, so be carefull to allow for the position with the pedals at full travel?
4. When doing your stress calcs, remember that you may not be able to do the necessary heat treating at home to relieve the steel and get full
strength in HAZ near your welds.
Foa your midi, consider having the fuel tank and battery at the front (if you have space) to move the weight forwards.
Hope some of that's of use
Regards
Hugh
Thanks for the pointers.
I think in this country there is no issue with fabricated uprights so I don’t really have an issue there. The intension is that the car will be for
both track and road but I was aware of the pedal/centre-line of the wheel rule but equally am going to go right up to this.
Regarding fuel tanks, I intend using quite a small one, possibly fitting it down the centre tunnel (would be called a transmission tunnel in a front
engine car) I think MR2 do this?
As for heat treating, I’ve heard that if I braze the axle in this will have less detrimental effect.
I’m going to try and get some bits together over Christmas and will post some pic’s when I have
Ivan - 23/12/10 at 08:07 PM
My biggest concern is where the axle goes through the upright - this would be the point of greatest stress with the least material to withstand it
due to the great big hole you have cut in the tube. Even if you have welded in the axle I would seriously look at some additional reinforcing in that
area. Also perhaps some gussets where the steering arm joins the tube.
orton1966 - 24/12/10 at 07:03 AM
quote:
Originally posted by Ivan
My biggest concern is where the axle goes through the upright - this would be the point of greatest stress with the least material to withstand it
due to the great big hole you have cut in the tube. Even if you have welded in the axle I would seriously look at some additional reinforcing in that
area. Also perhaps some gussets where the steering arm joins the tube.
I did have a similar concern, not because a hole has been cut through the tube because I deliberately designed the axle to be quite wide at the point
passing through the main tube and welding (or brazing) this in will replace the strength lost through cutting the hole. My concern was that I didn’t
want the axle to be too thin walled, equally I didn’t want it to be solid as it passed through the tube. The differential of thickness was what I
didn’t like.
One solution I came up with was to externally butt the tube i.e. start with some 3mm wall seamless tube and turn the ends down to my chosen wall
thickness leaving more meat in the middle where the axle passes through, see pic:
I’m not concerned with the steering arm because this will be designed so that the weld area extends to about half the circumference of the tube.
Once I’ve fully dimensioned the model I’m going to try a bit of structural analysis on it, which should be interesting !!
[Edited on 24/12/10 by orton1966]
atm92484 - 28/12/10 at 07:16 PM
Why not boxed plate construction instead of tubing?
It is easier to make it stiffer for the same weight since you can easily increase the moment of inertia.