I'm after some opinions/knowledge about the tapered holes in uprights to locate the top/bottom/steering ball joints.

I'm designing my own custom uprights and initially I'm going to be using the standard ball joints i.e. Escort TRE, Transit Drag Link & Maxi bottom ball joint.

Each of these have subtly different tapers on the spigot(?) bit. Sorry for the techy term... I don't really know if that's the correct name for it; the bit that has the taper on and the nut does up onto.

So...

1) should I be trying to get the holes in the upright machined to the exact taper dimension of the relevant BJ?

2) machine the upright to something sensibly close as the BJ's will sit "ok"?

3) machine the upright to what I feel then machine the tapers on the BJ's to match?

I'm not an engineer by any means so I'm looking for a good steer (no pun intended) from those with much better knowledge.

To my mind number 1 would be less hassle but when modelling the upright how do I know what size/angle to use.

Number 2: I've a sneaking feeling that this area needs to be accurate to work correctly. Am I wrong about that?

Number 3: Would be ok apart from the extra hassle in needing to re-machine the BJ's when they need replacement.

My intention is eventually to use spherical ends so will be making up some "connectors" which I could then make to my own taper spec but for now I'd like to finalise my upright design and get it over to my mate who can prototype it in plastic on a CNC.

[Edited on 15/6/2009 by andyd]

1) the ideal route

2) will create large local forces. They need to fit properly.

3) how do you intend to remachine the part? Youd have to dismantle the balljoint and then find some way to hole a cone with a ball attatched to it? not really possible and also an arse to do every 10k when they wear out.

personally it would be 1, or nothing for me.

quote:

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Originally posted by alistairolsen
how do you intend to remachine the part?

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you can hold most things in a 4 jaw chuck, not that tho I dont think.

if you held it by the thread then youd kill the thread and be unable to get the tool in for the joint flapping around and if you held it by the joint then the ball can bend and turn so that wont work either.

If you dismantle them all (6) then you might be able to, but I really wouldnt consider it, especially as I think they are hardened and plated anyway.

The vast majority of automotive tapers are 1:8 ratio, it's just the diameters that vary. Go to the Sidem web site and Search By Car. E.g. search for Ford / Cortina-Taunus / 1970-1982 and then click on one of the joints. Both upper and lower are 1:8 and 15.3mm small end. Then go back and find Ford / Transit / 1965-1985 and click on Tie Rod End (there's two listed - you'll work it out) and see that it's also given as 1:8, 15.5mm diameter and 18x1.5 thread. Tada, usable top joint Now, this one was obviously already known (duh!) but if your on the search for other suitable donor parts this may help. The one thing you will see is that almost everything is either 1:8, 1:6 (rarer), 1:10 (rarer again), or not tapered (straight shaft held by a pinch bolt).


With regard to your questions, as others have said, the taper absolutely has to be right! Near enough is definitely not good enough in this case.


Hope this is helpful,

Dominic

Excellent info guys, thx.

I do have some DXF drawings of the various parts plus I have the actual parts lying here on the floor next to me but the drawings dimensions differ from the measurements I can get using a caliper so just needed to make sure.

I don't want to get my uprights CNC'd with the wrong taper as my subconscious was telling me that was bad... just needed someone else to confirm.

Don't get stuck on the idea you have to use tapers --- pinch bolt fiitings are probably easier to machine to a sufficient degree of accuracy without specialist tooling.

Spherical bearings with rubber gaitors can alo be used as on the later Caterhams --- the key is to use a high enough quality bearing that will have enough endurance to be fit for purpose.

http://locostbuilders.co.uk/viewthread.php?tid=20446&page=1

might be of interest...