Drag link and tie ball

[jddevel]

Whilst the original "ball" was attached to the drag link and drop arm with castellated nuts and split pins is it now suggested that nyloc nuts are used? My drag link to drop arm came with just and ordinary nut - no split pin etc in sight !! I`m not looking at originality. Plus what size/thread are the nuts please.

[Steve Simmons]

I don't see why a nylok or self locking nut couldn't be used if you can find them in the correct thread. Or you could drill a hole for a pin. The thread is 3/8 BSF.

[Ray White]

Can I take this a bit further and raise the question of using these ends at all?

I have purchased (at some expense ) new track rod and drop arm ends which I have attached, I believe, correctly. I subsequently discovered that what are called "rose jointed" ends, with no spring loading - and therefore no movement - are fitted for better handling.

I am beginning to think that this is yet another example of style over substance. Some owners are unwilling to change ANYTHING from the original; regardless of advantages on the road.

[Rob Reilly]

My TA has regular nuts on the ball pins, no split cotter pins. They were not loose when I took them apart for restoration.

Split cotter pins and slotted nuts is one of the earliest design solutions to the problem of nuts working loose. But in terms of labor time the nuts and drilled shanks are costly and slow to assemble.
Nylock nuts, crimp nuts, deformed nuts, prevailing torque nuts, and all manner of lock washers are all later designs which are faster to assemble on the production assembly line, where time is money.

There is an engineering philosophy that says any fastener that doesn't work itself loose is a good fastener.

Isn't the idea with these ball ends that you snug them up so there is no axial movement, just swiveling?

IMG_20210622_161801772_HDR.jpg (47.53 KiB) Viewed 2660 times

BTW the rose joint is also called the spherical rod end and the Heim joint.

[Steve Simmons]

There is nothing wrong with the original ends. The spring loading helps to protect the relatively fragile BC box from road shock. Proper adjustment procedure is to run them down tight, then loosen to the first pin slot. The drag link end has only one slot, so I like to machine a second slot for finer adjustment.

Regarding rose joints / heim joints, I wrote an article on this very subject a while back. You can rear it here: http://www.tcmotoringguild.org/techinfo ... native.pdf

I make a few comments about original versus modern within the article, but the bottom line is (in my opinion) that either is perfectly fine for the average TC owner / driver.

[Rob Reilly]

A bit of trivia on the names, and an answer to why didn't MG use Heim/Rose/spherical ball joints on the TABC.
The spherical ball end was invented in Germany and developed by Messerschmitt in the 109, so the British only became aware of them when they shot one down in 1940. The allies passed the technology along to Rose Bearings Ltd in the UK and the H.G. Heim Co. in the US.

[jddevel]

Steve, Reading your article I`m curious as the layman why is chromoly TUBE used as apposed to a solid rod. Does it naturally absorb more flexing or some other mechanical benefit?

[jddevel]

Having looked at the Rose/helm joints -not being familiar with the term before (or forgot-I`m of that age!!) I now see why tubing has to be used.

[Rob Reilly]

One could use this kind if you wanted a solid rod.

[jddevel]

So is there a mechanical reason why tube is suggested rather than rod?

[Steve Simmons]

Using a tube gives you a larger diameter using the same amount of material as a solid rod. This results in a much stronger part at the same weight. If the rod was solid then it would not only cost more but would weigh a ton. As I understand it, most of the strength in a rod is at the outer diameter. The original size rod was prone to bending because of the small diameter, so using a larger rod fixes this issue. In casual driving this isn't really an issue, but I put a lot of hard miles on my TC and I did actually bend the original track rod.

If you were to use a solid rod of a larger diameter, then you would need female rod ends as Rob pictured above, but they would be much too large to fit the steering arms.

[Duncan M]

I got a new drag ball and end balls from Amsteer 7 years ago. They came with nylocks, yet were pre-drilled for a split pin. I found some proper grade castellated nuts and pinned them. While nylocks are just fine for many places on a car, I decided this was not one of those places. That (steering arm) drag ball showed much more wear than the other balls, when the old ones were removed.

[jddevel]

Thanks all. Decided to reassemble as is for now whilst sorting out parts for Steves` conversion. My wife doesn`t do "hard driving" but car will hopefully be back on the road for summer and will review for next winter after a "shakedown" period.

[jddevel]

Now I have a dilemma! I`ve received a report that the use of rose joints has made one particular car far to ridged and difficult to operate. Admittedly the point included the remark "a car with wider tyres". Any one have any similar experiences please?

[Steve Simmons]

I'm not sure I understand how that could happen. The only operational difference between the two is that a little bit of play is eliminated. I suppose it's possible the person could be feeling more road vibration and shock in the steering wheel because the springs are no longer there. Perhaps that's what he means by "difficult to operate"?

There is nothing wrong with the original setup. People have driven on it for decades. I had tens of thousands of miles on my original rod before it bent, and that was the result of some very hard miles. The solid ends are just a way of increasing performance for those who feel they need it. Driving for coffee on Sunday mornings, there's really no need to change anything in my opinion.

[Ray White]

Remember, if you go over to rose joints you must replace ALL the ends or fouling could cause the problems that you describe.

[Rob Reilly]

A mechanical engineering question!
I'm a retired mechanical design engineer, so this is fun, a chance to get my hand back into the profession.
My tie rod is 5/8" diameter x 31" Length between the end fittings.
So r = .3125" and L = 31"
The modulus of elasticity of steel is E = 29.5E6 psi
Moment of inertia I of a round rod is pi r**4 / 4
I = 3.14159 x (.3125)**4 / 4 = .00749 in**4
Euler's column formula for the critical load is Pcr = pi**2 E I / L**2
Pcr = (3.14159)**2 (29.5E6) (.00749) / (31)**2 = 2269 lbs
So a force of 2269 lbs exerted on the ball ends would just begin to bend the tie rod like a bow.
For a tube you take the outer I minus the inner I.
Let's try a tube 3/4" dia x .065 wall.
I = 3.14159 x (.375)**4 / 4 - 3.14159 x (.31)**4 / 4 = .00828 in**4
But using the heim/rose joints the length between them is going to be more than with the original ball end fittings.
Better assume L = 35"
Pcr = (3.14159)**2 (29.5E6) (.00828) / (35)**2 = 1968 lbs
So a 3/4" OD x .065" wall tube would just begin to bend with a force on the ball ends of 1968 lbs, in other words slightly weaker than the original 5/8" round bar.
The next size up is 3/4 x .095 wall.
I = 3.14159 x (.375)**4 / 4 - 3.14159 x (.28)**4 / 4 = .0107 in**4
Pcr = (3.14159)**2 (29.5E6) (.0107) / (35)**2 = 2543 lbs to bend
So you would want to use a 3/4 x .095 tube in order to be stronger than the original tie rod.
But there is a disadvantage with a tube, in that any damage makes it much weaker in bending at the damaged place.

[Steve Simmons]

That's an impressive amount of math that I won't attempt to double check! The tubing I used was 0.156" wall so quite strong, and similar if not slightly more weight than original. Beyond that, I don't know what type of steel was used on the originals or how strong or weak it is compared to the cromoly tubing I replaced it with. I do know that the original rod has quite a bit of memory, as I had to over-bend it to get it straight. The replacement rod is kind of impossible to bend without a press. I can't see it ever bending in normal use.

[Duncan M]

Just a pic to show the castellated nut on the newish rod end ball.

[Rob Reilly]

Well, Steve, you made a good choice with 3/4" OD x .156" wall tube, because your Euler critical buckling load is 4271 lbs.

Just to be clear, any 5/8" OD tube would have been weaker than the original solid 5/8" rod.