Krauser Top Case Repair

[Solina Dave]

This is a bit of a long shot, but any ideas would be welcome.
The photos are of a late '70s Krauser top case. As you can see the plastic trim, on the corner of the lid, has separated. I believe that the plastic is ABS. Over the years, with a lot of use, the lid doesn't fit as well as it used too. When it's closed, there's a lot of tension at the damaged point, so simply trying to pull the two ends together and gluing it doesn't work too well. A small piece of plastic installed and glued might work.
The design of the lid, where the top mates with the bottom, doesn't include a whole lot of material area to work with. I'd like it to look as nice as possible if I can.
Actually, the photo was taken from a case that I spotted on Ebay, but the damage point is identical to the damage on my case. It must be a common problem. It just saved me a trip out to my frozen, snow covered shed to take a photo of my own case.
Give it some thought, and thanks in advance for any ideas.

Thanks......................................Dave

[Dusty Boots]

Have you tried contacting Krauser UK to see if they possibly can get/have trim still available for it, Dave?

[Solina Dave]

Have you tried contacting Krauser UK to see if they possibly can get/have trim still available for it, Dave?

Dusty, I contacted Krauser in Germany last year to confirm the plastic as ABS. They said that the case was from a long discontinued series, and even they had to dig deep to even confirm that it was ABS. It took them a week to get back to me, even with that information. I think that maybe they might have been very young, when the case was originally made. Ha!
I probably shouldn't have referred to it as trim so much, as it appears far more likely to be part of the overall production mold of the lid. So I think it's going to be more of a repair job, than a replacement. I was kind of hoping to possibly apply some kind of plastic filler to it, and then carefully shape it, sand it, and paint it, if you know what I mean. Almost like applying some form of industrial strength caulking that would set hard. Maybe someplace that specializes in materials used by model builders would have something appropriate. I never thought of that before.

Thanks anyway for your interest Dusty, and I think that there might be a little bit of spring in the air.....................................Dave

PS..........I just Googled this site. It seems to have a considerable selection of possibilities. http://www.megahobby.com/putty-filler-supplies.aspx

[dingdong]

I would think that the common method for repairing ABS cracks would work just as well in your case. A slurry of ABS cement and ABS black pipe.

Read here. viewtopic.php?f=4&t=3246

[Dusty Boots]

Dave, you might want to try using some PC7.
I had very good luck with it repairing some cracks and melted plastic on the bike (trunk behind the back rest and cubby pocket standoffs) 6 years ago and it's still holding up very well!
You can get some at Home Hardware.

Tip ... use the tip of a soldering iron to melt a small groove down the centre of the moulding on each end of the broken part (as indicated by the red line in your photo), to give more surface area for the PC7 to adhere to!

When it starts to harden, you can mold it, sand it and paint it to match, etc!

[dingdong]

Keep in mind that the problem is shrinkage of the top cover. The lower is aluminum, no shrinkage. You are going to have to "fill" the crack in the top cover to fix this. Heating with a soldering iron won't work. You have to "fill" the crack.

[Dusty Boots]

Sorry if I wasn't clear, but that is/was the idea. The grooves in the edge of the plastic trim is just for the PC7 to grip better, due to increased contact area. Add some tape to the inside radius and fill the gap, then sand/mold it after it's hardened up.
Like I said, it works very well

[Solina Dave]

Dingdong, your point about shrinkage is certainly valid, and no doubt is probably a huge factor in the failure of the case at that point. I realize that the gap will have to be filled to allow the whole structure to be under less strain at that point.
And Dusty, I understand where you're coming from in regards to working the thin edge with a soldering iron, to create more surface area for the epoxy to adhere too. It's difficult, or almost impossible to see in the photo, but there isn't a whole lot of backing surface to confine the epoxy to the space that needs to be filled. The PC7 epoxy looks like what's needed, and in the description it says that it won't adhere to wax paper, so I'm thinking that I can carefully work a wax paper backing in there, fill the gap, and then after everything hardens, remove the wax paper. After that, my expert sculpting skills will come into play.

Thanks to both of you for your interest...................................Dave

[MikeB]

I have found that the best filler/repair material for ABS is either Plastex at http://www.plastex.net/ or Plastaid http://www.plast-aid.com/. I have used both and they are quite similar though Plastex is a bit superior. Using this material saved me quite a bit of money a year and a half ago when I was repairing my GL1800 after an accident. Look at the You Tube videos on this stuff. You should be able to Google both of them as get a great tutorial.

[FM-USA]

Tip ... use the tip of a soldering iron to melt a small groove down the centre of the moulding on each end of the broken part (as indicated by the red line in your photo), to give more surface area for the PC7 to adhere to!
When it starts to harden, you can mold it, sand it and paint it to match, etc!

I have been SUCCESSFULLY repairing plastics for quite a while now (since early 1970's).
One of the biggest challenges is stress areas. As plastics age they constantly dry out and shrink. Nothing can be done to add its original moisture, I've tried and I have asked the MFG's.

But you are not stuck, I'll offer my OLD secrete.
On the exterior, use strong tape to pull the parts together (bungee cord also helps).
Check for fit on the lower box before doing this repair, it is difficult to undo.
. . ALLRighty thennnn . .
As Dusty said, melt a groove but here's my added suggestion.
Get 1 or 2 pieces of stripped, copper house wire #14 or #12 gauge. Your repair looks like it needs about 3-5 inch long wire. You know more what it looks like and its stresses. Longer is overkill. Also you can pound this wire flat but not paper thin.
Use an electric soldering gun to melt that wire into the plastic. BE CAREFUL NOT to melt through to the finished side. Only need the wire just deep enough for the plastic to start flowing over the wire, no need to fully bury it.
__ NOTE: The bigger the wire, more heat is needed = high chance of melt through.
Once cooled, look at the outside for your acceptance. Reheat to re-position if needed.
Either melt more plastic over the wire or DEEPLY knife-cut many different angled grooves so the glue or epoxy has 'tooth' to grab.
Extra glue/epoxy over the wire to give more support. Here you can add more wire but that will be overkill and extra weight. You will know what's needed.
___ BTW: Stranded house wire isn't strong enough. I tried but ONLY works on very small parts.
I prefer 30 minute 2 part epoxy so material gets into the cuts and it sets quick enough so you can tilt the box to flow the epoxy where you want it instead of tooth-picking it in place.
. . NOTES . .
Once it's all done dab color match paint over it all and it be hard pressed to see it... but not necessary.
I did my Wing's top box 2.5 years ago like this and I've carried 30 pound bags of dog food on it, it's still holding.
I also have knife cut and epoxy the my side cover pins. 4 years later they are still holding.

HOPE THIS HELPS

[raven41951]

FM is right on. As a plastics engineer (yes there are such people), let me give you a little background. ABS is a copolymer of Acryonitrile, Butadiene and Styrene. The Acrylonitrile gives it rigidity the butadiene is rubber for impact strength and the styrene is to reduce cost. It is commonly used in refrigerator liners.

Over time, UV rays cause the chemical bonds to degrade which FM relates to correctly as it losing its flexibility. A plasticizer is used in some materials such as Vinyl to improve "softness" but it does actually leave the material as it is blended and not part of the molecular structure and is not used in ABS.

The best cement I know of for ABS is the ABS pipe cement used in plumbing. Epoxy works as well but only bonds the surfaces whereas the cement becomes part of the molecular structure at a cost of decreasing polymer chain length which makes the overall material less rigid.

Using a soldering iron or other appliance to heat up the material is also an excellent method, but precautions must be taken. ABS is a thermoplastic, that is it can be re-melted again and again. Re-melting also causes chain length degradation so care must be taken. You can get a good flow at 400 F. Colder than 350 will not give enough mixing and over 500 for any length of time will destroy the molecules. I recommend using a rheostat to limit the heat of the iron to about 500 F, which requires a thermometer capable of reaching 600 F to check the actual temperature.

I also agree with FM's take on reinforcing with wire. Any material only repairs will be temporary at best as the material is already aged. Like us, it only gets more cranky with age and eventually needs some type of external support, whether it is glued or melted into place.

Hope this helps.

[FM-USA]

ONE FORGOT'N MENTION...
Using epoxy on ABS, do keep the layers thin. The two materials expand and contract at different rates. Over time the temperature cycles will work the bond loose. Hence the reason for deep multi-angled cuts.
.
Thanks raven.
I'm not a chemist but I do test materials to see what they can/can't do.
.
The ABS plastic when either over heated or too many cycles degrades to either a brittle chunk that falls apart with a finger nail or just starts to powder.
ABS is a odd mixture of materials but I like how well it holds up to minor impacts and bounces back.
I believe if ABS could be very thin sheet laminated, it be a fantastic body panel material. Tho due to the rubber it would be a small pain to get the average Joe's paint to stick.
.
I have "Melt Sewing" non-compatible plastics with some success but it takes a lot of heat until you get a short rhythm.
I did this "Melt Sewing" on a cast iron intake with steel welding rod. It worked but not for strength. Would'a love to see the mechanics face when he popped of the carb on my old Ford van. A replacement EGR valve was BOO-COO Bucks and was cheaper to just plug that hole. Got better fuel mileage out of that!!!

[Solina Dave]

Well it was a bit tricky, but I'm done. I'm finding that if look at it from a distance, and I kind of squint my eyes a bit, it doesn't look too bad for a 37 year old case. I used the PC7 epoxy, some fine sandpaper, and a dab of flat black Tremclad. I placed a shim of tape in the slot before doing any work, to allow for minimal tension at the repair point. I brought the 2 ends together as much as possible, but I still had to fill a 3/16" slot between the 2 ends, and then sculpt it as well as I could after it set up. After the epoxy had fully cured, I removed the tape, and now the lid closes perfectly with no stress on the repair. It seems quite solid, and I think it will perform very well. I've included a couple of before and after shots. The bottom shot was taken 2 1/2 years ago. Don't be too critical please!
Thanks to all of you for you assistance, and your interest. It's much appreciated. Spring's just around the next curve, so get ready.

Thanks again.................................Dave

[dingdong]

I see nothing to be critical about. Good work.

[WingAdmin]

I agree, without an extremely close examination, I don't see any repair at all. It looks great!