Florida Build - PM Based


#21

Those of us undertaking the PacificMeister build have to contend with the tiny gap between the motor and the very slightly larger outer tube housing into which the motor slides. These walls need to touch to keep the motor running as cool as possible. Rather than relying solely on heat paste to fill this gap I have found that the metal from a Miller Lite beer bottle fits just about perfectly. Be super careful cutting the bottle as the metal is extremely sharp. I may still use a thin coating of heat paste to ensure a really tight fit.

Beer


#22

Another good alternative is 0.3mm silicone heat pads to transfer the heat.


#23

Isn’t that an insulator?


#24

Electrically yes, but they are designed to transfer heat between chips and heatsinks, much like thermal paste.


#25

Nice love the use of material! We did something similiar, but used aluminium tape instead.


#26

I have tested several substances to seal the wires as they pass through the rear mast clamp. This is a critical step because it’s the only thing keeping water out of the “engine room.” After the substance dries there will be a fair amount of flex on the wires (and the surrounding filler) as the clamp is pressed into position so it cannot crack or peel under stress. So far I like the silicone best since it adheres well and also flexes without failing.

Here’s what the silicone looks like on a test piece: https://youtu.be/GnUwgPrngyE

Any other suggestions are welcome!


#27

I userd marine silicone from Bostik. What I also do is to epoxy a 15mm carbon pipe for each cable. The carbon pipe has a very tight fit to the cable.


#28

Among the nice things of this solution:

  • excellent thermal conduction
  • cheap, cut with scissors, not sharp
  • easily available in the local DiY shops (insulation)
  • you can tune the fit depending on the number of tape layers, a tapered fit with a step cut… :smiley:
  • durable but not permanent if need be

The glue is supposed to be temperature resistant (150 to 300 deg C) but the glue water resistance status is not guaranteed so if 2 stuck pieces can stay for a few hours in a water glass (fresh and salt) it’s even better.


#29

I considered metal tape but was concerned the adhesive might provide some level of insulation.


#30

It’s a trade off:) still like your approach better, using regular household stuff.


#31

I had the same thought. What if you would wrap common household aluminium foil super tight around the motor? This has no glue and with a good fit it should not unwrap


#32

See my post , i went from 40mm to 45 then to 50 for the motor and the gearbox : 38mm to 40 with tape then to 50 with tubing


#33

As i understand it multiple layers of tinfoil can trap a slight amount of air between them which will act as an insulator. Thus the snugger the fit the better from a heat conductivity standpoint so you might find the foil tears when you try to press the motor into the tube.


#34

I did something similar to create a mechanically tight fit for the three wires as they pass thru the rear mast clamp before adding a waterproofing substance. I placed the little rubber rings from THESE PG7 cable glands around each of the three wires and forced that into each hole for a very tight fit.

Glands


#35

Indeed, the air is the problem. So it is quite important not to trap any air when applying the tape, getting some kind mini bubbles of air sealed by the glue.


#36

For my experimental build I will add alu-tape and then heat the alu-tube using a propane toarch. The diameter of
the tube will increase when heated. I then, faster than lightning, put the motor in the tub. “Shrink-to-fit”. Sounds easy in theory but will most likely be extremely painful :slight_smile:


#37
  • Disassembly will be pretty hard
  • You might melt the o-rings

#38
  • Disassembly is not an option. Its a glue-only approach :slight_smile:
  • No o-rings used.

See “the other way around”


#39

Yes applying heat to the tube should make for a very tight (permanent?) fit. I have pieced together my drive pod in a manner that allows for enough extra motor wire so I can slide the motor all the way out of the tube and detach it from the wire harness using the existing connectors on the 56104 motor. This required use of the full 1-foot length of the STANDARD tube. This also allowed me to avoid the issue of reworking the wires coming out of the motor that has caused problems for some.


#40

In initial tests running the motor+gear full speed for six minutes it was the gearbox (Neugart PLE40) that generated the most heat by far. This concerns me because, while the motor has the outer tube to act as a heat sink, the gearbox is mostly shrouded in the PLA printed sealmount which surely acts as an insulator. Ideally the sealmount would be a machined metal part like @cristophe did. I do have a machined (aluminum) motor gearbox mount that should help a little.