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[BreezyB]

I'm not sure what section of "Electrics" this should go in, I'll explain!!!!.
My first boat is now completely finished and so is getting a fair amount of lake time. I am very pleased with the result and it performs better than expected. However there is a gremlin which has become a mystery!!.
Every now and then while on the water , the motor "Hiccups" (Or stops for a fraction of a second) and then carries on OK.So far it isn't a problem because it hasn't actually stopped altogether. All connections are new and have been checked and have been "wriggled" during a bench run but nothing has shown up.All radio TX and RX and ESC are new also new.
As the problem seems to show up during maneuvering e.g when performing figure of 8 etc and I did wonder if the TX signal is dropping out as the RX antenae is around the inside of the hull (Balsa) but I am reluctant to go for an external whip.
So, if I give you the spec perhaps some one would suggest what the cause may be or what I should be checking.
Boat.. GG's Higgins Hellcat 24" Balsa Hull
Motor..Graupner Speed 400 Geared 2:1.  (Capacitors fitted)....New
Prop.. Graupner 3 Blade 40mm Plastic
RX..Futaba Sky Sport 4 . 40FM Number R136F...New.. Antenae attached to around the inside of the hull away from the motor.
TX..Futaba Sky Sport 4 . 40FM..New.
ESC.. Mtronics Viper Marine 20...New
I would be grateful for any ideas,
Regards
Barrie.

[Robert Davies]

Hello!

There are a few causes of this 'hiccuping'....

RF interference.

Receiver power 'brown outs'. ie Insufficient voltage and/or current being supplied to the receiver.

My money's on RF interference. The primary culprits are: improperly suppressed drive motors, servos, and metal to metal drive surfaces (as in gearboxes, metal geared servos and the like). In my experience mtroniks ESCs generate almost no RF noise incidentally.

First off, please describe *exactly* how the  motors are suppressed. Indeed if you could supply pics of the general arrangement of the control gear it may be easier to make recommendations.

We'll see what we can do to help!

-Rob

[andrewh]

Hi, Breezy

This is a great day - Hellcat sailing (even if not perfectly)

All that Rob says is true and valid, and I would have to add one or two more possible causes

I have had Mtronics ESCs that give this glitch - but its more of a long stutter and I have put it down to the internal overheat protection working momentarily  - the cure was a smaller prop (to lower the current draw)
I don't think that's your problem, but if you fitted a much smaller prop (just to try) that would eliminate that as a possible cause
Muck in the gears - a shred of ply or something like that can seem like an electrical problem
Transmitter connections  - especially the aerial .  Sometimes the aerial screws onto a male thread in the Tx, with a RF wire trapped under a tag by a thin nut (sorry - not good description) so the aerial is well tightened and making good connection to the screw, but the RF lead is wabbling about something chronic and making intermittent contact.  At the very least unscrew the aerial , give the threaded end a little perservative (i use WD40 but that may start a discussion) and snug it back up again

As Rob says the rest of the possibles are internal sources of RF - metal to metal joints and motor sparks.

It it was the RX aerial it would occur with the boat in one particular orientation to the "driver", and with a balsa boat that is very unlikely.  But all my boat aerials have a vertical bit, (and GGs)

Pictures, WE NEED PICTURES .  It may not help with the diagnosis but we LIKE pictures!

I have forgotten were you are in the coentry  - can you try substituting anything to see if the gremlin goes with it?

andrew

[malcolmfrary]

At the risk of joining the "teaching granny to suck eggs club" again, I recently watched a very experienced model boater with a RX behaving marginally - it would stop on ocasions.  He took very careful aim with the aerial, pointing the aerial at the boat.  As the aerial is not a gun, the signal actually comes out sideways, rather than from the end, so he was actually making matters worse by sending the least possible signal.  If the boat was unconsciously being followed during the maneuvers it could be that it hit the dead node.
Does the problem happen at any range or only at some distance?
When it happens, has the boat been working hard?

[BreezyB]

WOW!! I'm so glad to have you chaps on tap, your respose to my "gremlin" was most welcome and thanks to andyh for your continuing support with my Higgins.
OK, I have breaking news....whilst going over some of your ideas , I checked the Graupner Gearbox gears (Nylon)  for crud, as Andy suggested, and found that the motor securing screws were quite loose. This appeared to have caused two potential problems which may be associated with the "Gremlin" (1) It was lose enough to jump a gear tooth occasionally (2) With the piggy back motor configuration, the motor casing was vibrating against the prop shaft tube (re Robs comment about metal to metal causing interference.). I'm not sure if this will cure the situation as I cant try it for a few days.Could this cause other electrical problems?.
However I have put a few pic together as requested to see what you all think. The wiring looks a rats nest because I have untucked them so they are clearer (well that's my story).
AND to answer your comments......I do point the TX straight at the boat!!, didn't realise I did this.  The Motor suppression is a Graupner kit,the large capacitor across the motor is marked 224Z and the two tag to case caps are marked 104.  The hiccup can occur at any distance and even after a few minutes in the water but its true that it seems to get worse after 15 Min's or so. Andy's description is probably more accurate, it is more like a stutter.

Thanks again for all your ideas. Hope the pis are OK (One is for andyh just to prove that I have really finished it!!!)
Regards
Barrie

[malcolmfrary]

The stutter having a mechanical source seems the best bet.
 Personally, I have yet to suppress to the motor case, and have yet to experience a problem as a result.  Care needs to be taken when applying suppression components because shunting a potentially interfering signal away from where it might just might shunt it to where it can actually do harm.  As the signals are being shunted to the case via the capacitors, it might be a good idea to make sure that there is a metallic connection between the motor case, the prop shaft outer and the battery ground.
Try it with the motor firmly fixed first, though.

[BreezyB]

Thanks , Malcolm, for your input, it is really appreciated as indeed are the ideas and suggestions from Rob, Andy and other Mayhemmers. I guess that I will start with the the motor fixing and go through your ideas in a process of illumination to find the cure. This will be a good addition to my "learning curve" !!!!. I'll keep you all posted. 
Regards
Barrie.

[maninthestreet]

Nice model - is it scratch built?

[BreezyB]

Many thanks for the compliment, "man in the street", it means a great deal as it is my first powered boat. I was a "yachtsman" before but now totally hooked on PT/MTB's.
The Higgins was built from scratch from one of Glynn Guests "freebie" plans in a past issue of Model Boats although I have changed its appearance slightly so that is is more like PT 209 who's history I am more familiar with.
I must add that being a Mayhemmer has been such an asset because I have had such good advice during the build which has prevented me from creating too many blunders. So thanks to all who contributed.
Thanks again for your comment. 
Regards
Barrie.

[andrewh]

Barrie,

Thanx for the pics - she looks wonderful, and will go well
The torpedoes are turned in balsa?

On the principle that "anything you can try without destroying anything is worth a try"  how about gently extracting the aerial (which runs really right round the motor) and either:
Run it aft instead of forrard
or
run it aft, out of the deck joint and (preferably) vertical somehow or failing that flop it around the aft deck.

The motor/gear seems to the Graupner (or similar) type and I see you have added 3 caps (to the one already fitted) so that should not be an issue
The S400 7.2 is the softest of the S400 motors, lowest current draw on a given voltage, unlikely to be a problem and shoundn't for a moment bother the Mtronics Viper Marine 20.  At a guess the motor is pulling no more than an amp or two.

I'm still inclined to suspect mucky radio signal - hence the suggestion to get at least part of the aerial vertical and away from the motor.
PM me if you think I can help
andrew

[BreezyB]

Thanks again Andrew.
The torpedoes are "sort of" turned in that I have a 10" ridged disc bench sander for which I made a jig to rotate the balsa dowel in, so that each torpedo was the same profile. It is quite crude but works surprisingly well.!!!.
And I appreciate your continuing offer to bend your ear if I run into trouble, I'll keep you all informed.
Regards
Barrie.

[BreezyB]

Good News Mayhemmers, thanks to all of your comments and suggestions, my motor "Hiccup" is no more, even after extensive running.
Obviously I tightened the motor mount and then checked each suggestion in turn which has led to a complete cure.
I would say that rethinking the aerial system and also NOT pointing the Tx directly at the boat has probably been the answer.
Anyway I can now enjoy my boat without the worry of it cutting out (well for now anyway!!) and it is all thanks to you guys who took the time to help. Many thanks,
Regards
Barrie.

[malcolmfrary]

I do like a happy ending