Tucker tie rod.

[Tacoman]

I recently purchased a 84 Tucker 1342. The tie rod from the bell crank to the front steering plate was damaged (at least once) and repaired by the PO. The repair was obviously an amateur job. It was spliced at one location with a butt weld and then a lot of reinforcing steel was welded on the tie rod. No obvious reason. Angles and a channel, it looks horrible and it comes pretty close to brake disk (1/4") but it does not look like it was rubbing. I am in the process of replacing it. Questions for the group:

Are these tie rods a chronic problem? I have seen posts where the term "sleeve the tube" was used. Is this generally done as a repair or is it intended as an upgrade? The original tube was 1.5 od and 1.0 id. Does anyone have any insight on what is going on? I have purchased and threaded the tube, bought new hiem joints so now would be a good time to reinforce the rod if there is any benifit.

Just looking at the tie rod I find it hard to believe that it failed from steering loads. As an engineer, nothing would come off my desk that would fail under reasonable steering loads. Either dry steering or from an impact load while traveling. To me it looks like it might have high centered on the tie rod. Does anyone know why these rods generally fail?

Anyway, I am hoping to get feedback on best practice from the forum.

Any help will be appreciated.
John

 

[DAVENET]

Consider it a 'safety' feature. It can obviously be 'over engineered' so that it would never fail, but that is only pushing the issue to the next parts down the line. Which are much more costly, or in older machines, no longer made. It comes down to operator error. The hydraulics can overpower the gripping ability of the track system. The weakest point is that tie rod. Solution? Never turn the wheel while stationary.

 

[sno-drifter]

Believe what DN said. You want the tie rod to be your fuse. This is common when the left front hits an immovable object. happens too when plowing with a blade. Rule #1 DON'T TURN STEERING WHEEL WHEN STOPPED. The rod you are using is fine.

 

[DAVENET]

Rule #1 DON'T TURN STEERING WHEEL WHEN STOPPED.

Sometimes you try to turn it and get your hand slapped.

 

[Tacoman]

Thanks for the thoughts. It sounds like the tie rod can break just from turning the steering wheel when stopped. It makes you wonder why Tucker didn't put a pressure limiter or pressure relief valve in the steering system. There may be a reason why they didn't but it is not obvious.

 

[DAVENET]

Cost. And viably reliable technology of the time. Much easier to provide clear instructions (which MANY didn’t read) and sell replacement parts. The rods probably don’t ‘break’ often, but they certainly bend. Mine even had the glorious angle iron welded to it. That’s long gone to scrap. I’d rather just use my head and understand it is preserving parts made of unobtainium. Well, in my year machine, getting closer.

 

[Tacoman]

I am familiar with Rule 1. It has been brought to my attention at least 10 times. I don't want to be 15miles in and have the tie rod become a fuse. Also, losing steering at any can never be a "safety feature". I would much rather have a high hydraulic pressure limiter on the cylinder become the fuse. I am going to have to think about the best way of getting it done.

 

[chowderman]

incorporating a pressure relief valve into the system is an absolute duck soup piece'o'cake.
the tricky bit is to know what pressure to set it at . . . .

 

[Tacoman]

After giving it some thought it will get an adjustable, double acting relief valve (relieves in either direction). Plumbed to a T fitting between the extension and retraction ports. Any relief pressure will go back into the cylinder to the side with the lower pressure. That is pretty easy. I was thinking about setting it at normal operating pressure minus about 25% and working up/down from there. Does anyone know what the normal system operating pressure is? Bet it is 3000psi or less. There is some work ahead.

What could possibly go wrong?

 

[Blackfoot Tucker]

Tacoman,

A few years ago we reconfigured the steering system on our Thundercat project according to Tucker's suggestions which were the current setup they were using on a similar machine (long tracks and front blade). Pressure-wise, we increased the pump pressure to 2,250 PSI and ensured the priority valve rear cover on the hydraulic pump was putting out 6 GPM. We also installed a dual cross-port relief valve between the orbitrol and the steering cylinder. The relief setting was adjusted to 2,350 PSI.

Here's a pic of the installed valve.

 

[Tacoman]

Blackfoot
Good picture, clear information. That is pretty much what I was thinking. Additional question:
The relief setting is higher than the system pressure and that would lead me to believe that the tie rod failures were not from steering while stationary. My original intent was to prevent the tie rod from failing if someone tries to steer while stationary. The front tie rod on it has failed and been repaired at least twice. I have been told numerous times, including by the prior owner, that it can, did and does happen but I was a little skeptical. Is the tie rod failure issue really from hitting a stump or something while moving? I completely understand that steering while stationary is hard on the tracks, bogies, drive gear, belts, etc and should never happen.

This is what I had in mind and I think that is what you are showing in your picture. Sizing for flow and pressure are issues for another day. I still need to put a gauge on it to see the operating pressure.

Thanks and let me know if my thinking is right. Sorry if I got long winded. I appreciate the help.
John from Tacoma

 

[Blackfoot Tucker]

John,

As yet I haven't bent, or broken, a tie rod, so I can't tell you how they are being damaged. My recollection from the phone call with Tucker is when my machine was built in 1980 the pump output pressure was set to 1,650 PSI. Scott and I never measured it, so I can't confirm that number.

I've purchased a total of five Tuckers. Of those, only one has had a repaired tie rod. I don't know anything about your machine, but over the years these machines get operated by many different people with different levels of experience, and different levels of respect for equipment. My suspicion is that one, or more, operators of your machine didn't give it the care they should have.

I have considerably more experience snowmobiling than snowcatting, and I've hit too many fixed objects hidden just under the surface. The result was usually bent or broken front suspension/steering parts. So I've learned to be careful, and especially early in the season or when snow cover is questionable, I'm very careful when venturing off trail.

 

[Cidertom]

From the peanut gallery: The tucker tie rod issue(s) appear in quite a few threads. While the design should mitigate damage potential, my backhoe should not have been able to do this either. At max load it is too easy to get something in the system out of alignment and 'WELL POO".

 

[Tacoman]

I was concerned because this tie rod had been repaired a couple of times. This is my first Sno Cat. I have had a number of snowmobiles. Always Yamahas. In Central Washington a big concern is hooking a ski under a covered wire fence. They are hard to spot and are in odd places. A lot of the area is old abandoned farmsteads and range land.

 

[Tacoman]

From the peanut gallery: The tucker tie rod issue(s) appear in quite a few threads. While the design should mitigate damage potential, my backhoe should not have been able to do this either. At max load it is too easy to get something in the system out of alignment and 'WELL POO".

It looks like the job got stalled. I would not have thought that the cylinder could generate enough force to buckle the rod.