Adding an attachment point to a plastic material 2

[WCarpt]

I don't know if there is a better place to address my issue but I thought I would start here.

I need to add two more attachment points or "ears' to a plastic material on a cab of a tractor. Since the manufacturer did not properly space the bolts that attach an access cover to the cab, the thin plastic access cover ~0.01 inches thick bows substantially between the bolts which are spaced 16.5 inches apart, as a result of the pressure of the sealing gasket which then creates a sealing issue. The plastic material at the front of the access hole is 0.150 inches and the plastic thickness at the rear of the access hole is 0.137 inches thick. See attachments.

NOTE:I tried to upload several photos and a drawing but in the preview, it only shows one attachment, the last.) After posting, I found out that only the last attachment was attached so I will try to attach the photos. I found out I cannot add any more attachments! I will try the image function above.

What is a feasible way to do this? Try to form a piece of metal to conform to the area at the edge of the hole which would be difficult and cement it to the plastic for an additional attachment point or perhaps there is better way.

Thanks

 

[Compositepro]

RTV would glue the panel in place and make future removal very difficult. That is why I recommended plumber's putty. It does not cure and has no elasticity but lots of plasticity. It will assume the shape of the gap and without retaining any elastic stress pushing the gap open. If the gap moves the putty flows but stays attached to the wetted surfaces, maintaining a seal. There are also similar non-curing rubber materials available as rolled-up narrow strips sold for weather sealing. These are commonly used on campers and RV's. But these rubber products do have more elasticity and are harder to squeeze.

 

[MikeHalloran]

If you wax one of the surfaces, the cured RTV should be a little easier to release, and may serve as a semipermanent gasket.

But I agree, for repeated opening, some kind of putty/caulk is a better choice, provided you keep a supply of the caulk handy for service.

Or do pretty much anything appropriate, and tape over the closed assembly.
Duct tape is ugly and hard to remove.
Same for most packing tape.
3M brand blue tape is surprisingly weather resistant if applied dry, and is still removable after months of exposure. They offered a plastic-based 'exterior' tape for a while, but it didn't work all that well. Just the regular painters tape is fine.

Last winter, in CT, I skirted my travel trailer with 3M blue tape and most of a 3 foot by 50 foot roll of house wrap. It survived the winter well, and removed easily from the trailer's polyester composite skin. There are a few patches of adhesive still visible, but I think Goo-Gone will take care of them.









Mike Halloran
Corinth, NY, USA

 

[Compositepro]

The problem with using a waxed surface is that it prevents wetting between the sealant and the sealant surface. Therefore sealing can only occur if contact pressure is maintained. That is how a gasket works, which is what is used now.

 

[berkshire]

wcarpt,
This sounds like a job for a good automotive body and fender shop that has the capacity to fabricate intricate automotive parts.
Since you are not a metal fabricator , it sounds like it is time to turn the job over to someone who is. Who knows if you get a good solution you may be able to sell it to other tractor owners. It looks to me that a metal doubler ring using the original Pemsert / Southco locking insert holes may be the way to go, remember that is just an opinion.
B.E.

You are judged not by what you know, but by what you can do.

 

[LL631]

If the problem is just the cover bowing then a simple fix could be to make something like part 21 to apply more even pressure between the bolts.

Two lengths of flat bar with holes either end that attach to the outside of the cover with the bolts would do.

 

[itsmoked]

Excellent idea LL!

sendcutsend is a custom laser cutter with crazy reasonable prices! I get stuff cut there for less than I can get plain rectangular sheets cut to size. They can cut you stainless, copper, brass, cold-rolled, hot-rolled, titanium, the list goes on and on.

You provide a drawing in any of a dozen formats and the common ones will auto quote you online. Less common drawing formats they get back to you.

You could draw a stiffener as LL631 suggests (#21 above) that is the entire perimeter of your cover as wide as it can be and drop it on top of the cover and screw the original bolts thru it. The laser cut would, of course, include the existing holes. Use 1/8" stainless or even thicker if desired.

Alternatively dump the idiot cover entirely and replace it with a stainless plate that can't bow.

Examples:

0.125" SS

0.5" Cold rolled

SS

Keith Cress
kcress -

http://www.flaminsystems.com

 

[WCarpt]

Thanks for your additional input. Adding a stiffener would work for the top piece but another issue is the bottom opposing piece bowing with pressure. Although it has a tendency to deform less with pressure than the top access cover, I have to take it into consideration also. As you might guess, this is on a New Holland tractor and a person doesn't examine the top of a cab before buying to catch engineering snafus like this.

 

[itsmoked]

Yes I can imagine. Very, VERY, annoying to find issues like that on expensive machinery. I've seen MANY in vehicles where the designers should be sent to hell where they have to live with their lazy screw-ups.

I understand your bottom flex issue but I suspect it will work acceptably with a soft gasket and a stiff metal replacement cover. AND, a critical eye while tightening the screws. This prevents both sides from having bowing low pressure contact in the middle of the unscrewed runs.



Keith Cress
kcress -

http://www.flaminsystems.com

 

[itsmoked]

Another thought. I use aluminum tape for lots of things. It's pretty amazing. I have it in high abuse areas and it's lasted for years. It is completely impervious to UV because it's.. metal. It comes in up to 18" widths I believe. It is highly conformal forming into dips and such. You could slap a piece over the entire area making sure it conforms as needed. If you ever have to get in again just peal it off and reapply a new piece.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[itsmoked]

BTW: The narrower the gasket the better it will work because the pressure will be higher than a wide gasket with allow with your mechanical realities. You probably know this though.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[WCarpt]

Interestingly, the gasket New Holland sent me as a replacement was 1/4" wider and was significantly firmer, which was totally unacceptable. I tried to tell New Holland it wouldn't work properly but was blown off---so much for New Holland's engineering excellence. I found the equivalent soft gasket after some research.

 

[TugboatEng]

I would avoid using neoprene gaskets to start with as they will harden over time. Silicone foam is available adhesive backed stripes and very soft formulations.