Cadet 123 hydro speed control
 

I ordered up a new cam and damper plate assembly for my Cub 123 hydro, and see a few potential issues. As I understand it, gradual self accelleration/decelleration is caused by play between the cam and damper, and any play between the damper and trunion will usually result in more abrupt jerking. My tractor exhibited a little gradual self-accelleration problem, and none of the unpredictable jerking I've heard with others running original speed controls of this age.

Anyway, issues with the new parts:

1. The post which engages the cam on the 903-0194 damper plate assembly is longer than the original, such that it protrudes well thru the cam plate. I believe it will interfere with the trans tunnel, and because the tunnel is not removable on a 123, so there's not much opportunity to test fit. Has anyone else seen this on a 123? I'm not sure whether to just grind it down to match the original, or if I should be exchanging it for another damper part number.

2. More interesting on hydro theory, I think I've come up with a new fix for the worn trunion problem. Both my old damper plate and the trunion itself have a slot that is 1.210" long. I'm not sure if that's what they were when manufactured, or if they've both just worn evenly to this number, but they work wel together. The tractor exhibits none of the jerking problems exhibited by hydros with worn trunions. However, the new damper plate has a slot for the damper springs which is only 1.190" long, resulting in 0.020" play in the spring assembly. I'm guessing this is the source of the jerking so many have observed, and the reason for the recommended trunion fixes.

However, it seems it would be much easier to simply file the new damper plate slot to match the worn trunion (1.210"), than to weld repair the trunion. The extension springs in the assembly easily hold in the 1.210" slot, and as already observed by using this tractor, the 0.020" difference in slot length seems to make no difference, assuming the trunion and the damper are well matched to one another.

Am I missing something?

Fix the trunion do not add wear to a new part, or in other words make the old like new not the new like old.

A lofty goal, for sure, but for what purpose? Is there some reason beyond self-satisfaction for making this fix more complicated than necessary? Finding the path of least resistance to a suitable solution is the art of engineering, not just blindly copying "the way it's always been done."

Sounds like you already have your mind made up, so if you don't want to listen to those who have had the experience with these tractors, why ask?

The 'jerky' motion comes from wear in the corners of the trunion slot, wear between the cam plate and trunion shaft, worn linkage, and broken/missing trunion springs. Welding up the corners of the slot, shimming the cam plate to remove axial play, and replacing ball joints in the linkage will fix the problem and are faster, easier/less complicated, and cheaper than what you are proposing. This is the path of least resistance because it's been tried by many people and we know it is a cheap repair with a high likelihood of success. Why re-invent the wheel? The 'way it's always been done' as you call it has been refined by many people over the years trying different things.

Fred's 123, I think what you are missing is what causes this problem. As it has been said for a long time, "a picture is worth a thousand words" Look at this link http://onlycubcadets.net/forum/showthread.php?t=4635
Is that what your working on?

Thanks for the link, Clay. What I had missed was the significance of the notches at either end, upon which the spring retainers can catch. My trunion has them, and they're quite pronounced, although they didn't seem to be causing me any trouble (yet). In any case, I guess I better repair that trunion.

So, what's the recommended fix? That IH Trunion Repair Slot for $9 at ccspecialties would appear a good way to go for an amateur welder, unless someone knows otherwise. I'm much better at sticking parts together with the welder, than artful building up areas or filling in voids, as I only break out the welder roughly once per year.

Any trouble with the trunion shaft seal, after heating the trunion up with the welder?

Thanks!

" I'm much better at sticking parts together with the welder, than artful building up areas or filling in voids, as I only break out the welder roughly once per year."


Get a piece of flat copper, the thicker the better.

1/8" will do, but, I use 1/4" thick 'cause I got it.

Clamp it behind the part and weld!! You will be amazed how well you can build up!!

That copper will fall right off after welding. Watch out, the copper will be HOT!!

Grind the weld to the finished shape you want.

:beer2: Try it, all your friends will be envious of your "skill". :bigeyes:

Don't tell them about the copper, it will be our secret!!
:biggrin2:

You can weld up the corners much faster than you can weld that repair piece on. Make sure to wrap a wet rag around the trunion shaft so you don't melt the seal.

Okay guys, I'll give it a shot! I've done a bit of filling using the copper plate trick, and each time I get really good at it right about the time I'm finishing the project. Then the welder goes back on the shelf for 10 months while I forget everything I learned, until the next project comes up.

Just moved, so I don't have the big compressor rigged up yet, or even a garage receptacle for the welder. Will get moving on that tomorrow, and let you know how it goes! Might get away with running the die grinder off my small portable compressor, for this small project.