Melted firewall

[basslord1124]

Yeah everyone has some good suggestions. I'd look definitely at what @Dante says in terms of the center hole. That could be rubbing slightly enough to generate heat either by friction and by drawing more current. So definitely check that the motor spins freely and is not rubbing. And then next I'd check the prop size. Feel it after use and see how hot it is. Also, get a watt meter to see wattage and current.

I don't know much about 3D printers but plastic with a higher melting point can help.

 

[CPJ]

Have you checked that the hole in the center of the firewall is not rubbing on the c clip? I have seen another instance somewhere on youtube where the c clip wasn't spinning with the shaft and was rubbing against the shaft creating heat. Now I drill the holes extra big

Yes. I checked that and actually had to embiggen the hole a bit.

 

[joelspangler]

I'll be curious to hear if your embiggement of the center hole solves the problem.

 

[CPJ]

I'll be curious to hear if your embiggement of the center hole solves the problem.

No, I had made sure it was large enough to clear before my first flight.

 

[TEAJR66]

An 1806 on 3s with a 6x3 prop is a hot setup. Not a bad setup, just a little on the warm side. For most 2300kv 1806’s, 3s 6x3 is well within specs.

PLA does not handle heat well. It works fine. Just expect it to not like a lot of heat. I run some hot setups on PLA firewalls and I get some deformation over time. Not a huge deal because most of my foamies don’t last long anyhow.

Going to 2s or propping down to a 5x3 with your 3s battery should cool it down enough. Extra airflow can’t hurt.

Otherwise, be prepared to melt a few firewalls. Not a huge deal.

 

[CPJ]

An 1806 on 3s with a 6x3 prop is a hot setup. Not a bad setup, just a little on the warm side. For most 2300kv 1806’s, 3s 6x3 is well within specs.

PLA does not handle heat well. It works fine. Just expect it to not like a lot of heat. I run some hot setups on PLA firewalls and I get some deformation over time. Not a huge deal because most of my foamies don’t last long anyhow.

Going to 2s or propping down to a 5x3 with your 3s battery should cool it down enough. Extra airflow can’t hurt.

Otherwise, be prepared to melt a few firewalls. Not a huge deal.

Well, when they melt enough for the screws to pull through.....it’s kind of a bummer. 😬

 

[TEAJR66]

Well, when they melt enough for the screws to pull through.....it’s kind of a bummer. 😬

Yep.

 

[CPJ]

So. Tried a new prop on a new firewall and a new pod.
Flew 3-4 minutes, all going good then thpppptptttttttttttt. Motor started vibrating. Heard it, and chopped the throttle. Expertly landed in a nice soft tree. 🙄 Firewall got hot, screws backed out. Again.
Got the new motor in today too. Comparing them by simply spinning them, the old one seems to have a touch more resistance and feels a bit more “notchy.”
I suppose I’ll give the new motor a go and see what happens. If I still melt the firewall, I guess I’ll drop to a 5” prop? What size is going to be easier on the motor? I’m new. I dont need speed. I need my motor to not fall off mid flight. 🤣
I suppose the good thing about this is that I don’t need a huge battery. I never fly long enough to drain the one I have.

 

[TEAJR66]

5x3

 

[CPJ]

Put it on my bench and let it run. 2 minutes in the plastic was melted and the screws backed off. New motor didn’t change anything. Leads me to believe I’m over propped. Motor is 3-4S rated, I have a 3. I have a 30 amp SC, 20 is recommend. So I’m not pushing it that way.
2 shops in town, neither had the as recommended above 5x3. So it’s ordering stuff again this week. I’d have bought the specific flite test motor to begin with, as I would LOVE to support them. But every time I tried everything I wanted was out of stock.
Anyway, for now I whipped up an aluminum firewall, if it melts that we
are in giant trouble. Certainly going to bench test it again, I’m tired of crashing.
Used a printed wall for the template. No, it’s not perfect, but functional.

 

[CPJ]

It just doesn’t end. Attempted to glue the aluminum firewall to the pod. Didn’t stick for anything.
Grrrrrrr

 

[CPJ]

Bunch O punch marks didn’t help either.

 

[Hai-Lee]

Just a thought! If the motor is getting hot and thereby heating the mounting screws which in turn heat the PLA and allow the screws to pull through the melted plastic, why don't you use thermal barriers to allow the motor to be mounted to the printed firewall without transferring the heat from the motor to the firewall.

A fibre washer would provide a heat transfer barrier between the motor and the firewall. An air gap around the mounting screw would reduce heat transfer from the screw thread to the hold through the firewall and finally another fibre washer would prevent heat transfer from the nut to the firewall.

Whilst you would need to obtain some fibre washers and slightly longer mounting screws the result would allow the motor temperature to soar without melting the firewall. In addition the larger diameter of the washers would spread the "pull" of the motor across a larger area so the firewall if still subject to a little softening from radiant heat would be less likely to fail as currently.

Have fun!

 

[CPJ]

The washers have been mentioned, I’m just not sure where to find them, locally at least. I’d think an old circuit board would make some decent washers, cutting them roundish would be the trick.
Actually, and old PCB might make for a decent firewall. IF it would stick to the hot glue.
Tried drilling holes in the firewall as well. NOPE. Just ended up making a studded glue mold. 🙄

The options currently are wood, or the fiber washers. I sooooo detest wood, but it will at least stick and not melt.


Cool. Figured out the pictures.

 

[Hai-Lee]

Where such a heat problem exists I often just use up some of the spare inserts that I end up with from the many props I have used over the years. I prefer the inserts that come with the GRP props as it doesn't melt the same as regular plastic.

Nothing to cut out! Heat resistant and they provide the isolation I require. Failing that you could use a bits of paddle pop sticks to lift the motor mount off of the firewall and to cut Aluminium firewall down in size to fit on the inside side of the firewall and isolate it in turn from the printed firewall with a few more pieces of paddle pod stick.

Just a few thoughts!

Have fun!

 

[Hai-Lee]

Yet another thought, you could go to your local electronics distributor and grab some TO3 mounting kits. They use a few insulating feedthroughs to provide electrical isolation between the TO3 case and the heatsink and can normally withstand quite high temperatures!

Have fun!

 

[Wildthing]

I haven't had to many problems with my 3D printed mounts until lately screws coming out. Now what I do is add a drop of CA glue to the screw and then put it in. My mounts I also print at 3.5 mm thickness , double wall minimum and 30% infill. I also see no vent holes in your mounts , I always have 2 minimum to make sure air can travel past the motor.

If the motors are hot hot you need to prop down no matter what.

 

[CPJ]

I haven't had to many problems with my 3D printed mounts until lately screws coming out. Now what I do is add a drop of CA glue to the screw and then put it in. My mounts I also print at 3.5 mm thickness , double wall minimum and 30% infill. I also see no vent holes in your mounts , I always have 2 minimum to make sure air can travel past the motor.

If the motors are hot hot you need to prop down no matter what.

You hit on what I just realized....no vents. My motor is smack up against the firewall, no space between and no way for air to flow from the back. That could be my
Issue right there. I’ve made a firewall from wood, “flew” it on the bench for 10 minutes. It’s hot, but it survived. What I’ll try next is spacing it off the firewall, letting the motor breathe. Or just adding vent holes.
But first this evening, I’m FLYING THIS DANG PLANE. I get the build fly crash repeat, but I’ve had a gut full of build and crash.
Thanks again to everyone who has chimed in. 👍

I had to mill down a chunk of mahogany to make my firewall. Didn’t have anything near thin enough.

 

[Wildthing]

That's a load of work for a mount LOL, hobby shop or Micheals and get some 3/32" plywood

 

[CPJ]

That's a load of work for a mount LOL, hobby shop or Micheals and get some 3/32" plywood

It took maybe 5 minutes to find it and hack it down. I’ve got a hobby lobby fairly close, but not getting out in traffic and doing it faster than I can drive there and back is a win!