custom made trailing arm

[uninformed]

well If I can get the nod to do my TA/Body rigger mount, Im going to have to make new longer arms. Once again im offering up an idea for some technical cretique.

I am thinking of getting some OEM arms (already have them) and using the axle end. Using 45x25 CHB (carbon hollow bar) as the main body for the arms, I would bore the end so it suits the 27mm OD of the OEM arm, for what ever length was possible and required. Slip the new CHB over it and weld where appropriate. For the pin bush at chassis I was thinking of doing something like the track rod/drag link ends. That is to have a threaded end go inside the CHB so it can be adjusted. Once set it is clamp bolted so it cant move. The pin outside will be exactly the same as LR (20mm dia 20x2.5 thread), then a short body with 2 flats machined on it for adjustment, then the section that goes inside the CHB say 27x2 thread with 75mm of length.

I will try and attach the CHB specs and see pics for my quick drawings and photo of clamp bolt end.

[wagoo]

Serg, I don't know how much difference it would make, but later LandRover steering rods, even though they occasionally (all too often on coil sprung Rovers) strike offroad obstacles, were obviously only designed to withstand tensile or compressive loads, so full length and exposed threads as used on LandRover steering rods from series 3 onwards were deemed acceptible.
Because trailing arms are more likely to make contact with Terra Firma, exposed threads may be deemed a weak point. Earlier series 1 and 2 steering rods and TRE's didn't have full length threads. A plain unthreaded section near the balljoint of the TRE spiggoted into the plain counter bore on the end of the steering rod tube, so shear forces were focused there instead of the root of a relatively sharp thread. I would design the threaded connection of the trailing arm similar to the early TRE method.
Bill.

BTW. I want to compliment you on your artistry with the cardboard chassis components.

[uninformed]

Thanks Bill

I figured the cardboard mock ups would be alot easier to discuss than my poor ability to verablize/type my ideas. It will also give me something to take to the sheet cutter/folders and see what way to approach it.

I havent seen a SI or SII in person, but I think I can get what you are saying. The smooth shank section, would this be the same dia as max dia of thread? or a touch larger?

Looking at some real would measurements, the ID of the CHB is 25mm, the OD is 45mm. The LR TA pin is 20mm. The min I can internal thread the CHB is 27mm fine (27x2.0, tap drill size 25mm) or 1 1/8 UNF, tap drill 26.50mm

Not sure if a fine or coarse thread would be better in this application?

How long do you think the spigot be? Remembering that the longer in it is, the further the internal thread has to be.....the deeper the thread the more ridgid the boring bar, the more ridgid the boring bar, the larger it has to be....maybe determining the ID??? (btw this is just a guess as im no machinest)

With this design, do I still clamp the new TA at the spigot, same set up as the track rod pic I added?

[wagoo]

Probably best go with Johns recommendation as to length of plain shank, providing he agrees that having one is worthwhile, but I would guess it should be a little longer than the width of the clamp. I'm imagining around 30mm. I think you would have no choice but to use a pinch clamp as your photo shows, because a jamn nut, which incidently keeps working loose on my FC 101 trackrod, would require a full length thread.
From memory the diameter of the shank was only a few thou up on the major diameter of the thread on the earlier TREs.
Bill.

[uninformed]

Rick may chime in here Bill, I seem to remember him telling me of a paper he read regarding F1 cars and going with a similar principle for rod ends...I think the bung with lock nut was deemed not to be as good.

yes was thinking 30mm plane shank, 25mm clamp (made from 25mm flat bar)

from your experience, how deep could one resonably internally thread in a 25mm bore before the boring bar starts to move??

[rick130]

Yep, a pinch clamp is preferable to a jam nut for fatigue life as it doesn't concentrate so much load at the root of just one thread.

Tony Southwall did that on the XJR9 TWR Jags at Le Mans just so they didn't crack any tie rods, as in motor racing we always used jam nuts on rod ends.
He did the numbers and it was pretty conclusive that a pinch clamp was a much better way of locking the TRE's and track rods, etc to survive the bashing over kerbs and wheels of a 24hr race.

I'm guessing they must have had the odd failure.

Good point re the plain section Bill, I didn't think of that.

[wagoo]

from your experience, how deep could one resonably internally thread in a 25mm bore before the boring bar starts to move??

Looking back, I can't believe how long it's been since I did any lathe work, and even then I used to just muddle through as I never had any formal training.
I'd imagine with a 25mm bore, you could have a fairly rigid boring bar a little under 25mm diameter.Just enough clearance to clear the swarfe away. The cutting tip could be of the adjustable cross sliding type.
Bill.

[modman]

Serg, I'm away in SA atm but would you believe I have those very pieces machined up allready!!
Made from 4140, the threaded sections and bush rings axle end
The arms I'm making are to suit 40x10 mm wall 20mnv6 (sp?)
I'm home in ten days if you can wait
I intended to use a ht nut tigged with ss wire at the pin end, then a lock nut to alter the length up against the TA
I'd run this design past an engineer and have the weld proc. documented, he seemed happy enough to pass in VIC.
Dc

[uninformed]

Hi Modman (Dave I think )

sounds good, im not going to be rushing. No new TA's unless I can do the new mounts.

Are you using the nut welded to the hollow bar instead of threading inside?

[uninformed]

20mnv6 is pretty much the same standard as the CHB im looking at.