Diesel engine cooling-radiator ghetto repair

For this years EMF camp I was traveling together with the belgian embassy. We had two busses filled with people and material to drive from belgium to the campsite and back.

One of the busses had a blown tire on our way, that was fixed by fitting the spare:

Blown tire

On our return trip however, we had a major issue. The radiator was leaky, as seen in this picture. The water on the road used to be in the cooling system.

busWe did discuss how to fix it. One option was to just put an egg into the cooling liquid, in the hope that the protein would coagulate and stop the leak. But that is a process we can’t control, so we switched our focus to other methods.

Next up was soldering. We had lots of solder-equipment with us, after all we were coming form a hacker-camp. But soldering on a heat-sink is doomed to fail. Perhaps we could have done it with a propane torch, but we did not have one with us.

All that was left was to glue it. I had some 5-Minute-Epoxy at hand. First we drained the radiator and dried it with the hot-air. Then some cleaning using wire-brushes and isopropanol was done. The epoxy was mixed and stuffed into the radiator with tootpicks and other pointy objects, then heat-cured with the hotair for 30minutes.

This is how it looked after the curing:

radiatorIts messy and ugly, but it did seal the leak. I did expect that it would still leak a little, but to our surprise it was perfectly sealed. The cooling system was even able to build up pressure again.

With that repair we made it back over the canal back to belgium 🙂

Scara Robot Repair – Learning stuff the hard way

Turns out the drives of my Scara Robot are not velocity-mode drives but torque-mode drives instead. Setting the drive input to a constant voltage results in constant accelleration. I learned this the hard way by crashing the robot :-/

Even though I had it fixed on an Europalette it managed to fall on its side. Second lesson learned: even ‘small’ a 200W drive can turn the whole thing in a fraction of a second. Hitting the floor broke some pieces. But see for yourself:

B-Arm and Z-Motor-Plate destruction
B-Arm and Z-Motor-Plate destruction

Those parts are both made out of cast aluminium. I do lack the equipment and skill to weld, so I asked a Friend of mine to do it. However, even with his long time experience he wasn’t able to fix the parts together. At first I got desperate and tried hard-soldering the Z-Motor-Mount. But even using two torches I wasnt able to get the part hot enough to accept the solder.

Z-Motor-Plate fixed with clamps ready to solder
Z-Motor-Plate fixed with clamps ready to solder

As a last resort I deceided to glue the parts. Fortunately my sister works as a postdoc and is an expert for aluminium epoxy bonds. She did some rought calculations for me and helped select the correct adhesive: 3M Scotch-Weld DP490.

I prepared the parts by grinding away all paint and about 100microns of the aluminium. The last step helps because cast aluminium has different properties on the outer layers compared to the inner bulk material due to the casting process. I also cut some reinforcement plates from 6061 Aluminium. Then I cleaned everything several times with water/soap and acetone. Everything was clamped down on a clean plate and glued together in two steps: First the two broken bits were fixed together. After curing the residual glue was removed by grinding, then the reinforcement plates were glued. To improve the curing process I put a box over it to trap the air inside and heated everyhing which a hot air gun to 80°C. Unfortunately I didnt take that many pictures of the process:

After that, I did some cosmetics. With a lot of car putty, grinding and even more putty and finally a red finish the part looked like this:

Fixed B-Arm with W-Motor already mounted
Fixed B-Arm with W-Motor already mounted

 

That concludes the B-Arm. Fixing the Z-Motor-Plate was basically the same. Here are some more pictures:

That concludes the repair. I will cover the mechanical and electrical rebuild in a seperate Blogpost.