Abs body cracks.

[LarryW]

Well I have been working on fixing my cracks and just thought I would post why these cracks are here. Well actually they where there when I got them. But I did make them worse. These cracks are the result of climbing logs that are able to fit between the tires. The worse one is fixed and I wish I would of tooken a picture of it but did take one of the other side today before I fixed it. I will post the fixed picture of it when I am done. Seems how this is abs it is a piece of cake to repair. Just soften the body up alittle with the acetone and spread the abs/acetone(50/50) mixure on. Let it dry. I plan on doing something to reinforce this. Kinda thinking maybe 1 1/2" angle iron on both side down bottom held on by some metal attached through the axle bearings. Maybe something in front and back across from 1 side to other to work as a skid plate from impacts. But that is all in the planing and might not do it.

I also repaired a hole I got when the chain popped and wrapped up on the center sprocket. It is on the bottom so Im not going to sand it but if it was visible it can be sanded down and if color matches will look like new. This was actually a hole,not just a crack. Like maybe 5mm x 10mm so it was small. But after like 5min it was done including prep. Then let it sit over night and good as new. Easy to fix but being abs is easy to break as well.

[JRP3]

How strong do the repairs seem to you? I've been doing the same thing and the ABS mixture never seems to get as hard as the original. If I really push I can get a fingernail to leave a small mark in the repair, but not in the original ABS. Also, the one repair you did just looks like a thin layer over the crack and I wonder how strong that will be, unless you also put some on the inside of it. I've been doing many layers to build the cracks up more.
I'll also be doing some sort of heat formed plastic, (HDPE) skid plate over the whole bottom as Hydromike did.

[LarryW]

Mine got hard enough to not stick the fingernail in. Im not sure why yours isnt. Here some suggestion that might help. Maybe its mixed to thin, like to much acetone? Maybe there is acetone trapped in the plastic. Try brushig acetone on it and let it dry and go back and do it again few time. Maybe adding a little heat to it might make it harder like hair dryer. Just make sure the acetone is dried for fire safety. Maybe wrong type of abs, I know there is more then one kind of abs but thought all worked the same. Im not a abs professional and just throwing ideas out. Hopefull one hits the ball.

It would be alot stronger when I goop up the inside but I just want it to seal water out right now. I kinda pried the cracks apart and rubbed acetone in the inside surface of cracks so hoping that help out bonding in between. I think it should be fine as long as I go around the logs. If not Ill fix it again. Just didnt want it getting worse. I plan on taking the frame out and putting more on it but its my only running attex right now. It is in between the frame and plastic gap so I can do it well without removing the frame. I'm going to get the 225/h going again first. Then I will get into more detailing/cleaning up/beefing up and stuff on the tt.

[JRP3]

The ABS is from another Attex. You might be correct about the heat, I've been working in a cold shop, thinking the lower temp would slow the acetone evaporation from the surface and give it more time to migrate out from the plastic. However that also slows the evaporation from inside as well. I'll try a heat lamp and heat gun and see if that makes any difference.
On the really thin cracks that I can't pry apart well I've been using a soldering iron to heat weld the cracks together before I put the acetone goo on. The heat welding alone looks pretty good on the small cracks but I don't trust it on it's own.

[JRP3]

Must be the temperature I'm working at. I hit it with a heat gun and as the plastic softened bubbles came popping out all over, even on the edges where the patch was really thin! I took a razor blade to an unheated section and sliced off a piece. Inside you could see pinholes everywhere. I guess this process doesn't work well at 35 degrees and lower
What temperature are you working at, and how often do you go back with the acetone brush?

[LarryW]

It has been between probably 30-40 degrees here so dont think the temp is it. And this last time I did it I waited like 5 minutes or so and then re-brush it. The mixture I have been using is from like 2 years ago. It is alot thicker/gooier then it was. I would always put in a splash of acetone in the can everytime I was done to help replace the evaporation level, but havent used it in a while. Maybe being thicker is the trick because I have had the problem before.
It seems like I read somewhere if you burn the plastic you are burning away something in the chemical makeup. Is it doing it at just the places you plastic welded or everywhere? To bad David Berger isnt around. He could probably help you better.

I took mine out yesterday and played a while and I did climb a log and it hit pretty hard between the wheels. I though it was big enough to just hit wheels but The plastic repair took the impact with out breaking even though its only gooped on the outside. If you could do both side and get it like twice as thick as the original it probably wouldnt matter having the bubbles.

[JRP3]

It has been between probably 30-40 degrees here so dont think the temp is it. And this last time I did it I waited like 5 minutes or so and then re-brush it. The mixture I have been using is from like 2 years ago. It is alot thicker/gooier then it was. I would always put in a splash of acetone in the can everytime I was done to help replace the evaporation level, but havent used it in a while. Maybe being thicker is the trick because I have had the problem before.

You mean the problem of it not hardening up fully?

It seems like I read somewhere if you burn the plastic you are burning away something in the chemical makeup. Is it doing it at just the places you plastic welded or everywhere?

It's only bubbling where I put the ABS goop on.

I took mine out yesterday and played a while and I did climb a log and it hit pretty hard between the wheels. I though it was big enough to just hit wheels but The plastic repair took the impact with out breaking even though its only gooped on the outside. If you could do both side and get it like twice as thick as the original it probably wouldnt matter having the bubbles.

I can't get to the inside without removing the frame. Not happening.

[George]

I've found that repairs need a great deal of time to reach their full strength. We're talking weeks...especially when the area requires a great deal of abs such as holes. I've also found that using the ABS as a patch helps. You need to soak it as a sheet and then apply it to the cleaned area. This works well when both the affected area and the patch are both flat up against each other.

[LarryW]

Well, I guess I should of just chilled a bit. Like weeks i guess. I got carried away today and cracked it all over again. Does anybody else have that problem with it cracking in between the front/middle or middle/rear where a log or something can fit inbetween and hit the bottom? I guess the poly bodies can take it better. I dont see how the maxIV or others with a larger gap in between the tires can take it.

[JRP3]

Yeah, I think the ABS is the worst, plus the fact that the ABS seems to get pretty thin on the bottom, especially near the edges and corners. The cut sections I have go from 1/4" thick on the upper flat front section to 1/8" thick on the bottom corners, where it really needs the strength. HDPE skid plate here I come.

[JRP3]

I did some research on the Oatey black ABS plastic glue. The ingredients are ABS plastic resin, colorant, and 2-Butanone, otherwise knows as Methy Ethyl Ketone, MEK. I tried some patches using MEK instead of acetone, with the same results, still soft after a week, bubbles up when heated So that's not the answer.
Last night I tried something a little different. I used a heat lamp to heat up the cracked area so it was nice and warm before I applied the ABS and acetone. Then I removed the heat lamp and applied the goop, and went over it after a few minutes with the acetone brush, then again a few minutes later. The idea is that the warm body would help push the acetone out from the bottom of the patch while the cooler air and surface temperature would keep the surface from curing and allow the acetone to escape. I'll see what it looks like today.

[JRP3]

Didn't seem to make any difference in the short term. See what happens after a week or 2.