Flex Shaft Installation

[Cutch]

I just got the motor, flex shaft and tube, strut and prop installed into the boat that I'm building. I have a teflon lined tube from the motor thru the hull and into the strut. On the stand, everything runs great. When I put the boat in the water, the prop barely turns. If I pull the boat out of the water, let the drive drain for a few seconds, it runs OK again. If I stick the prop into the water running it keeps running fine. If I only submerge the prop and strut, it works fine. If I lower it until the tube is in the water, the prop will hardly turn if I let it stop. Seems to get a lot of drag. I removed the teflon liner and it acts the same. Was it a mistake to run the tube into the strut so that it is almost sealed? Is moly grease a mistake? Can't see how I get so much drag, especially with the liner removed. Any suggestions would be appreciated.

[carlcisneros]

on the drive dog installation, did you file a flat where the set screw snugs up to the drive shaft at the front of the prop?
if you did not do this when you set it in the water, the drive shaft will spin and the prop will just sort of go along for the ride so to speak.

[Cutch]

Thanks Carl
Has a flat and everything is tight. Going to test if the brass bushing in the strut is shrinking enough to make the shaft tight. Let you know when I find it.

[Cutch]

It looks like I'm back to the drawing board. The drive is OK, no drag. Removed the prop and it starts OK. Lift the prop almost out of the water and it goes. In the water it turns slow for about 4 turns and quits. Seems the motor doesn't have enough starting torque.
Hobby King 3660SL 3060kv running on 2 cells(7.4v) with Octura X438 prop (1.5x1.4=2.10).
Any ideas.

[RIPFENCE]

is your flex coupler tight enough on the motor shaft? just checkin..if its not it may have enough grip to spin the prop when out of the water but it will not once submerged

[sailr]

Did you leave a little space between the strut and the drive dog? Flexshaft could be winding up and shortening.

Next cause is a bad motor.

[Cutch]

Everthing is tight and driving. Increased the gap. Still quits after about 4 slow turns.
Simulated a 3cell using a motorcycle battery and found that the motor starts up OK.
Looks like I need to go to higher voltage or less aggressive prop using this motor?
Maybe the motor is bad like sailr suggests?

[siberianhusky]

You could go higher on the kv for a 2s setup but something else is very wrong if it can't at least turn the prop in the water.
Can you post some pics of both ends of the setup? Are the connectors all soldered well? Might be a bad joint that can't handle the current.
Any kinks or flat spots in the bends in the stuffing tube? Could cause binding when the cable is loaded.
A good 3/16 space for the cable to wind up?
Thrust bearing on the motor? Cable wind up could be pulling on the motor shaft and binding, or pushing the other way and binding, thrust bearing prevents this one.
How easy is it to spin the cable not hooked up to the motor? Should turn very easily, does it make a "straight shot" into the coupler when you install the cable or do you have to force it in some direction?
Does the motor get hot at all when it stops? is it trying to turn still or does it just die at some point?
How about the esc? maybe it's not working right and can't supply enough current.
Tough one to diagnose not being able to see and more importantly hear what it's doing.
A few things to check though.

[Flying Scotsman]

It sounds like a bum motor, ESC or battery as it is only under a load condition, that you have the problem. Did you run the motor at full RPM on the bench for more than 2 seconds?

Douggie

[Cutch]

Flex Shaft Installation

Thanks again guys. I've attached 2 pics of the drive. I don't think it's the problem anymore. In the water, the prop will turn slowly 4 times about as fast as you can say 1 2 3 4 and quits trying. I found that I can easily simulate the water test by pinching the smooth end of the prop nut. If I let it get started just above starting you can't hold it back with frying your fingers with 7.4v. I tried the same with 11.3 volts and could hardly make it not start.
Yes I ran the motor full speed for about 5 seconds to tach it. Trying to learn. Hope the lesson wasn't too expensive.
It's really a pain to troubleshoot when the parts come from the other side of the world. Can't just try another part to find the problem.

[785boats]

It might be that the low voltage cutout in the ESC is set for 3s, & it is cutting out under load on the 2s pack. Did you set the LVC for 2s?
Cheers.
Paul.

[Alexgar]

good call 785 i think thats probably his problem

[Cutch]

Sure sounds like a possibility Paul. The following link shows that it is programable.
HK B200 A ESC
No manual with unit. I don't know how to program it yet. I'll be searching tonight.
http://www.hobbyking.com/hobbyking/s...dProduct=15134
Thanks for the help

[Alexgar]

try this manual

http://www.suppomodel.com/ESC/Normal_Airplane_ESC__50A_and_above.pdf

[Cutch]

I guess I have to wait for the right instructions. I'm running the motor on the elevator control on an airplane transmitter.
Found that the ESC would go into the first menu if I started at full throttle. Wouldn't go to second menu and morse codes by just going to neutral. Found that it worked by using the throttle control. Also found that full reverse on elevator also worked worked. After I got all done, I only have forward (weak like before) and now I don't have reverse. I noticed that there were more options in the morse code menus. Possibly the menus are different.
Maybe some news from Hobbyking soon. I'll post the outcome. In the meantime, thanks for helping.