Intercepter Ultra - fast motor,... heat issues?? Or not.

[TachyonDriver]

Completed the first sea trials earlier tonight. Yes that's sea trials with a letter C... OK OK C = canal! :D Any electrically minded nautical chaps or chapesses care to voice opinions please?

Anyway - she's running a 21 turn Ansmann Racing Clash 540 motor (9A draw 25,300 rpm @ no load presumably) hooked up to an mtroniks viper eco 20 ESC with a 7.2V 2000maH battery and BEC on the receiver. The Ultra has a high pitch 2 bladed prop.So, I had her tooling around the canal for about 10 mins, most of which was on full bore. I know electrics get warm, hot even, but how hot is OK, subjectively?

I burned my finger on the motor, but then again I've had slot car motors which have done the same and been alright. The battery was hot, but not so hot you couldn't hold it; if it was a li-po I'd be a lot more worried! The esc was warm so no worries about it's thermal cutout.

Is this too hot a setup? Should I limit high speed runs? I don't want to try and modify for water cooling - perhaps I should cut some vents in the upper deck? The motor itself does have cooling vanes which rotate near the comm - due to the type of mount in the boat, both vent holes in the motor casing are half exposed. Should I just expose one hole fully, leaving the metal clamp to cover the other one?

Apart from that, she looks pretty good!

Cheers,
Tach.

[pompebled]

Hi Tach,

If you burned your fingers on the motor can, try holding the motorshaft between the brushtabs next time and show us a pic of the blister...

If the can is thát hot, the armature and the commutor will be close to burning out after a few of such runs. Not to mention magnet degradation.

The air needs to be able to circulate through the motor, that's the purpose of the fan, if the slits are blocked, unblock them, airflow is cruicial!

Cutting slits in the hull will do very little for the cooling, as the flow will be rather low.

I know the motor mount in the Intercepter makes watercooling difficult, but cutting out the tray in front of the motor will create room for brushtab cooling, this transfers heat from where it's generated, the brushes.

The pic is of a 700 motor, but the principle is the same.

Regards, Jan.

[tim slocum]

How about something like this??

[P_J_Glor]

Does anyone have a diagram for the brush tab water cooling jackets? Those on the 700 motor pic look home made.

Pete G.

[pompebled]

Does anyone have a diagram for the brush tab water cooling jackets? Those on the 700 motor pic look home made.

Pete G.

They are home made, because there's nothing commecially available, why should they bother, a couple of pieces of 4mm brass tubing from the LHS is all it takes.

I'll make some pics of 'how to', if I find the time tonight, you search your gear together:

Tools & stuff:

- 80-100 W soldering iron.
- S-39 (soldering water)
- pair of pliers with rounded beak
- solder
- 4mm brass tubing
- wooden cloth peg
- motor leads.

The pics are rather self explanatory.

All items to be soldered together are tinned lightly to speed up the soldering.
The brass tube in the pic is way to long and should be curved on one end, so the silicon tube fits nicely without being squeezed flat.

A big iron is cruicial in order to be able to work quickly; the peg will prevent things from falling off when the solder gets liquid, but "baking'too long with a (too) small iron will over heat the brushtabs, making them softer, worse is the possible deformation of the plastic brushtab holders...

Let me know if you have questions.

Regards, Jan.

[pompebled]

Pics added.

[steveciambrone]

pompebled,
Have you had any trouble with shorting the motor? The water is shorting across the motor leads. Fresh water can have some conductivity, I suppose you have never run this setup in salt water?
Interesting approach by having the inlet point forward and the exit pointing aft. I just have the inlet aft of the propeller and let the exit squirt out the side of the boat. I like seeing the exit water so I know it is flowing.

Nice explaination on water cooling. I think some modelers who have never done it are a bit apprihensive about doing it the first time. But done once it is really easy. It can be hard to drill that hole in the hull where the water might come in. But properly sealed it is a none issue. One can always add an inlet at the transom and have it enter the boat well above the waterline.

Thanks
Steve

[pompebled]

Hi Steve,

You're right, I've never run this set-up in salt water, if I would do so, I'd have to make two seperate circuits, to make sure the distance between the two motor poles (through the water) is as long as possible.

I know from other boaters, that this way shorting isn't an issue.

The boat in the pic is an epoxy hull, so getting the inlet leakproof is no problem, with an ABS hull I would first glue some ABS sheet in the hull where the inlet comes to have more material to drill a tight fitting, watertight inlet, preferably use ABS tubing, so I can weld it into the hull and never have any leaks.

Like you said, having the outlet under water, leaves you with no visual control over the water flow.
I was apprihensive at first, but the sucktion is so effective, the cooling is more efficient than a spray pick-up.

Regards, Jan.

[LtDoc]

Tim,
Air cooling isn't as effective as water cooling, primarily because air is less heat conductive than water/metal, and because of the airflow required also means possible access of water where it doesn't need to be. Air cooling certainly works if a lot isn't required. Any heatsink that doesn't look like a porcupine isn't going to do a lot of heat transferring (bad way of saying it, but you get the idea).
- 'Doc

[pompebled]

Tim,
Air cooling isn't as effective as water cooling, primarily because air is less heat conductive than water/metal, and because of the airflow required also means possible access of water where it doesn't need to be. Air cooling certainly works if a lot isn't required. Any heatsink that doesn't look like a porcupine isn't going to do a lot of heat transferring (bad way of saying it, but you get the idea).
- 'Doc

As usual, you're right, doc, but in the boat in the pictures, the airfrlow through the armature by the internal fan, is the major cooling component, hence the large vents in the motor mount.

These boats run a triangular (30 x 30 x 30 m) course for eight minutes and achieve some 30+ laps in that time, as most of the running is done flat out, the fan in the motor does the bulk of the cooling, the 'plumbing' is just a bit extra, to keep the brushtabs as cool as possible.

Most important is to have the boat set-up correctly, only in a lightly moving boat, the motor can survive eight minutes full throttle racing.

Regards, Jan.

[P_J_Glor]

Thanks for the close-ups. It does look pretty simple on that motor. Mine has a more complicated brush set-up, but I get the idea.

Pete G.

[pompebled]

Thanks for the close-ups. It does look pretty simple on that motor. Mine has a more complicated brush set-up, but I get the idea.

Pete G.

Hi Pete,

On a motor with external shafts for the brushes, watercooling them is much easier, the brass tubes get soldered on top of the brush shafts.

I forgot to mention one important step in the pic post; before soldereing on the leads, attach the suppression caps first... (oops).

Regards, Jan.