No Joy Joystick

[gmason]

It's my opinion after looking at the break, that the crescent shaped piece of metal that the holes for the screws are drilled is made of cast metal and is brittle. Plus that the holes drilled into this part are so large that it doesn't leave much metal/strength for the forces that are applied to this point of stress.

I would think that eventually with the pushing, pulling, and twisting that the joystick takes, all will fail. It truly is the week link in the whole system. But as long as the dealer keeps supplying me with the replacement part /forums/images/graemlins/crazy.gif

We should start a email campaign to NH to resolve this issue once and for all /forums/images/graemlins/smile.gif

gary

 

[jtn]

I think the part is just not strong enough. As has been pointed out, there is not a lot of metal left once the hole for the screw is drilled out.

My last broken No-Joy-Joystick that was welded and strengthened is still going strong. Next time I am working on the tractor I will get a picture.

JT

 

[tc35dforme]

JTN,

Just took another look at my TC35D joystick.

The screws that hold the plastic onto the steel rod are installed into a metal riser that is made from what appears to be steel bar stock 5/8” x 3/32” that has been rolled along its length to a curved shape to match the riser shaft. It laps over the riser shaft about 1” and is welded.

The screw holes are maybe 3/16” leaving about 5/16” of meat on each side.

No cast metal on mine.

Mechanical engineers correct me if I’m wrong, but when the screw is properly installed, there is little weakening of the assembly. The screw in effect becomes part of the strength with a bit of loss due to the minor mis-matching of parts.

I wonder if New Holland changed this part somewhere along the line. Maybe some are cast and some are rolled steel ??

It seems that where the breaks are would not be where the maximum force would be. I would expect the maximum force to be on the shaft at the lower part of the plastic shroud assembly, not a inch or two up. Maybe NH is over tightening these screws on the line stress cracking the metal ???
/forums/images/graemlins/crazy.gif

 

[hazmat]

<font color="blue"> Mechanical engineers correct me if I’m wrong, but when the screw is properly installed, there is little weakening of the assembly. The screw in effect becomes part of the strength with a bit of loss due to the minor mis-matching of parts. </font>

Hmm, It depends.

You've got a plate with a tapped hole in it. You then "fill" that hole with a bolt (likely >strength then the plate). If you load the plate itself, it acts as a composite (ie more than one material) structure and has close to the same strength. You do lose a bit from the local stress of the threads etc.

However, if you load the bolt, not the plate it is a different story. Simply tightening the bolt to its specified torque loads it greatly. This creates stress on the threads and adds to the loading on the "system".

Summary, loose bolt, plate loaded = somewhat similar strength to plate w/o holes

Tight bolt, plate or bolt loaded = strength = plate with hole.

 

[markie61]

So.....
for those of us with business or humanity degrees..... /forums/images/graemlins/crazy.gif
Keeping the screw tight will reduce the likelihood of problems...?

I have taken mine apart twice to check and see no indications of stress - yet. The screw DID fall out on its own once, though.

Mark

 

[tc35dforme]

Hazmat,

Step away from the coffee pot ... you're getting too much caffeine ! /forums/images/graemlins/tongue.gif Can you run through that one more time....slowly ?

If the assembly is tight, screw tight against the plastic, plastic tight to support bar, and screw torqued properly for the thread standard....does the fact that the bar was drilled and tapped matter much ?

Now, if the assembly loosens all bets are off !!

 

[hazmat]

I don't drink coffee.

Looking back at it, my summary wasn't very clear. Here's another shot at it.

If the bolt is LOOSE and you are pushing on the PLATE only, The bolt / plate assembly will be close to the strength of a plate with no holes = doesn't matter much (to use your words)

If the bolt is TIGHT and you are pushing on the PLATE only, The bolt / plate assembly will be weaker than a plate with no holes = will matter

If the bolt is TIGHT or LOOSE and you are pushing on the BOLT, The bolt / plate assembly will be weaker than a plate with no holes = will matter

Clear as mud eh?

Bottom line, reinforce it if you can!

 

[tc35dforme]

Hazmat,

I think I get where your going.

You seem to be talking about a generic assembly and describing point forces applied at various locations relative to the assembly as a complete system.

I was kind of talking about the New Holland loader handle. /forums/images/graemlins/shocked.gif

I think we both are coming to the same conclusion though.

In the end....some work....some fail.

No offense intended by the coffee remark. Just a bit of light-hearted ribbing.

Thanks for the engineering lesson. Now to evaluate the effect of Jinmans hose clamp repair /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/grin.gif

 

[jtn]

Hazmat,

I was thinking the same thing about the tight screw doing more harm than good.

For those of you who do not know engineer speak disregard the the rest of the post.

When the screw is tightened it is putting a positive bending moment on the handle. Then a larger positive bending moment is added when the handle is pulled towards the operator. There are also Y axis bending stresses when the handle is pushed parallel to the operator. My guess is the material, with the hole drilled in it reaches its fatigue limit quickly.

JT

 

[jtn]

Come to think of it I am not sure whether mine is cast or rolled. Depending on what stock they are using I would think rolled would be stronger.

<font color="red"> It seems that where the breaks are would not be where the maximum force would be. I would expect the maximum force to be on the shaft at the lower part of the plastic shroud assembly, not a inch or two up. </font>

You are right, the maximum force is at the bottom but the maximum stress is at the screw hole as that is where there is the least amount of steel to resist the forces on the handle. Stress = Force * Area So small area equals high stress.

JT