UHMW recommendations

[ArlyA]

Yes it was in the sun over the winter months and in use. That's around 4 months here.

I asked this in a earlier thread and got no takers. Polys need to be attached differently than most products due to there high rates or dimensional changes in varying temps. Anyone interested in that here??

Was the HDPE on your groomer in a location that gets direct sun? Inside a chute should at least be shaded most of the time. I think I'm going to install something in one my chutes before next winter.

 

[FatTire]

Yes it was in the sun over the winter months and in use. That's around 4 months here.

I asked this in a earlier thread and got no takers. Polys need to be attached differently than most products due to there high rates or dimensional changes in varying temps. Anyone interested in that here??

The dimensional issue was covered to some extent to in the thread which is linked to in post #20 of this thread. I was just going to make some slots in the long dimension for the mounting holes and leave the fasteners barely snug. Is that sufficient?

 

[ArlyA]

Yes but cutting slotted holes is tough for most folks to make. We do several things. Limit the size of each piece, then leave some space between them all for expansion. We also drill overly large holes for whatever fastener we use as apposed to the slotted ones you mention. Then use a nylon crown lock nuts on the fastener plus a washer under it.. On 3/8 wear pads we used 1/4 countersink head screws. Then in the steel plate they to mounted on, drilled 3/8 or 5/16 holes for the 1/4 bolts. And we do not tighten these countersink headed screws or on any fastener you might use down. Washers and nylon crown lock nuts are your friends when working with this material..

 

[FatTire]

Thanks Arly, nylon lock nuts is just what I was thinking. I have a long list of projects this summer, looking forward to them.

 

[dnw64]

...nylon crown lock nuts are your friends when working with this material..

Good idea. Thanks.

 

[bob 59912]

I used 0.030" UHMW polyethylene tape that had a pressure sensitive adhesive on one side on the flange of the snowblower chute and the hold down blocks to make it rotate easier. After a season of blowing here is what it looks like:

I ordered the tape from ePlastics (a.k.a. Ridout Plastics) as 1/32" "slick Sticks" in 1" and 2" widths in 50 foot rolls. Used 12 segments of the 1" width to cover the flange and then trimmed the excess. Did the same to the underside of the chute hold downs (seen in red with the bolts). Used a hard roller to attach the UHMW pieces at 60F in my garage.

Plan was to also use the 1" and 2" pieces to also line the blower area and the inside of the chute (lengthwise). Given previous threads here I had some concerns about how well it would stick with the cold temperatures here in Montana and then putting the tractor with plow and blower back in a 60F garage after clearing the snow. I also wondered how it would hold up against the pressure of the snow / ice and from the gravel on the road and driveways that I clear.

To test this I added a strip sideways near the exit of the chute to see how well it would hold up.

As you can see the strip stayed in place, with no signs of it detaching anywhere, after all the blowing done this winter here. I'll line the chute and the blower fan area this summer without any fasteners.

ePlastics also has thicker versions, 1/16" and 1/8", of the UHMW PE tape with adhesive on one side than the 1/32" I used. It comes in widths from 1/2" to 24" wide.

ePlastics also has sheet material w/o adhesive in thicknesses from 1/8" to more than 4"

 

[dnw64]

According to coefficient of thermal expansion specs I found (11 in/in/ｰF x 10(-5), a 24" piece of UHMW will move 0.29" from -20 to 90ｰ F.

My thought is to attach the chute piece solidly in the middle when it's about 35ｰ. Now the ends are going to move +/- 0.075", or roughly 1/16", meaning that 1/8" oversized holes would be sufficient.

Or, the bottom could be attached with a "clamp" type hold down:
_______________
___\/___| =================
------------------------------------------------------

The \/ is a bolt, the _______ is a bent sheet metal piece, the ====== is the UHMW and the ---------- is the chute.

The "clamp" wouldn't be tight, just hold that end down so that the snow couldn't get under it. If you used thick enough UHMW the top could be done similarly, but you'd probably want to cut a "dado" for the clamp piece so that it was flush or slightly recessed from the surface of the UHMW

 

[FatTire]

Thanks everyone for contributing to the body of knowledge -- outside of TBN I wouldn't have been aware of the magnitude of the expansion/contraction issue. I'll be doing the chute work in the summer so I would have had a surprise next winter.
I am surprised by the results with the UHMW tape, appears they've really got the adhesive figured out.

 

[ArlyA]

Here is a HPDE shoe (or ski?) i added to an implement some years ago. I can't recall if its 3/8 or 1/2 thick but was heated and bent to this shape you see. The three bolts at the lead are carriage type and tight. The reaming ones were left lose.

 

[dnw64]

At what temperature does poly become formable? Is it feasible to put a small piece in an oven at whatever temp works good?

Or how did you bend that piece?

 

[ArlyA]

I have no idea what temp it becomes pliable at. If you look up HDPE in Wiki and I'm sure its listed there. I bolted this piece on using the three lead bolts. Then using two or three head guns, warmed the steel up from the bottom side. (implement was upside down for this) This does take some time to make it all hot enough and the plastic evenly warmed up at the same time. After the temp seems high enough, using a piece of wood against the plastic, bent it down with a few clamps and hold it in place.. After its firmly clamped down, then spray some water on it all to lower the temps. If you didn't get it warm enough, it will pop back to its original form quite a bit. Its not a very easy process to do.

 

[dnw64]

I have no idea what temp it becomes pliable at. If you look up HDPE in Wiki and I'm sure its listed there.

Good idea!

Its melting point is around 130 to 136 °C (266 to 277 °F)

Not sure at what point it becomes "plastic" but it seems like maybe 200-225° would be a good starting point.

Wish I didn't have so much other stuff to do this year, there's lots of interesting Tractor stuff to suss out and do...

 

[bob 59912]

Garland Manufacturing, a maker of extruded UHMW-PE has recommendations for heat forming parts, as well as other "tabs" on that webpage covering UHMW-PE bonding, annealing, machining, and FAQS.

 

[dnw64]

Garland Manufacturing, a maker of extruded UHMW-PE has recommendations for heat forming parts, as well as other "tabs" on that webpage covering UHMW-PE bonding, annealing, machining, and FAQS.

Thanks!

:thumbsup: