Model Boat Mayhem - Forum

Technical, Techniques, Hints, and Tips => The "Black Arts!" ( Electrics & Electronics ) => Topic started by: CJ on June 28, 2012, 11:19:39 AM

Title: what have I done wrong ??
Post by: CJ on June 28, 2012, 11:19:39 AM
Just taken the boat out after fitting water cooling to test...........water cooling didn't work, even after following instructions and other posts on here..

(http://s16.postimage.org/5o31c9rup/IMAG0180.jpg) (http://postimage.org/image/5o31c9rup/)

(http://s15.postimage.org/w31xb835z/IMAG0182.jpg) (http://postimage.org/image/w31xb835z/)

Can someone offer any idea what is wrong ??
Title: Re: what have I done wrong ??
Post by: john44 on June 28, 2012, 11:39:40 AM
Hi CJ, pitty about your cooling not working,
you seem to have done everything correctly.Are you using silicone tube from your pick-up, & outlet as it can tend to
collapse on tight bends closing off the tube. just a thought.

john
Title: Re: what have I done wrong ??
Post by: essex2visuvesi on June 28, 2012, 11:46:30 AM
can you post some pics of your cooling layout.  I had problems when I put the outlet too high up and there was not enough pressure
Title: Re: what have I done wrong ??
Post by: unbuiltnautilus on June 28, 2012, 12:13:31 PM
To work effectively, the pick up needs to be directly behind the rotating disc of the propeller, not neccesarily on the centreline, and not directly behind the prop hub. this ensures maximum thrust through the pick up. Natural flow as the model moves through the water is not enough in itself to push the water up the scoop and around the system.
Title: Re: what have I done wrong ??
Post by: Perkasaman2 on June 28, 2012, 12:13:31 PM
Relocate the inlet pickup on the centre line of the prop and shaft with a few mm's of clearance from the spinning prop. You must use the thrust of the prop wash to force flow for cooling. I would also increase the size of the opening in the pickup fitting but without shortening it any further. The fitting ideally should be a little longer to obtain the full effect of the thrust from the tip of the prop but it will probably be ok providing you enlarge it's opening.  :-)
Title: Re: what have I done wrong ??
Post by: DickyD on June 28, 2012, 12:24:48 PM
I'll go with the majority on this. your inlet tube is to short and it should be just off centre of the prop.
Title: Re: what have I done wrong ??
Post by: ACTion on June 28, 2012, 01:09:06 PM
It would also be a good idea if you can contrive for the hole in the inlet to face directly into the flow. The one shown is at only 45 degrees which not only reduces the potential pickup but is in danger of allowing Bernoullli's Effect to create 'negative pressure' and actually suck the water out of the inlet. (Go on, Dicky - read it up on Wickipedia!).
DM
Title: Re: what have I done wrong ??
Post by: Martin [Admin] on June 28, 2012, 01:21:02 PM

Before you change anything, I would suggest you  put it in the bath with only a short bit of silicon tubing  connected to the pickup tube and hang it over the transom, rev up the motor and see if you get any flow of water.
Title: Re: what have I done wrong ??
Post by: Circlip on June 28, 2012, 02:04:07 PM
Nay Martin, that's a common sense approach  {-) You'll be telling us next that he could also fine tune the system to get maximum flow using the same method.  %%

     Regards   Ian
Title: Re: what have I done wrong ??
Post by: CJ on June 28, 2012, 03:42:33 PM
Thanks guys,

I have found a kink and small split in the silicone tube, which may have contributed....but I do like Martin's approach before drilling out and putting more holes in the hull  <:( .

Will try and bath test and see what happens ......if not will have to go for something far more drastic !!!

Will let you know what happens !!

Cheers

CJ
Title: Re: what have I done wrong ??
Post by: CJ on June 28, 2012, 04:18:42 PM
some pics of the cooling over on the refurb posting can be found http://www.modelboatmayhem.co.uk/forum/index.php?topic=37569.0

CJ
(http://s13.postimage.org/sfzl89w4m/IMAG0151.jpg)
Title: Re: what have I done wrong ??
Post by: DickyD on June 28, 2012, 05:59:31 PM
It would also be a good idea if you can contrive for the hole in the inlet to face directly into the flow. The one shown is at only 45 degrees which not only reduces the potential pickup but is in danger of allowing Bernoullli's Effect to create 'negative pressure' and actually suck the water out of the inlet. (Go on, Dicky - read it up on Wickipedia!).
DM

Come on Dude, you know my problem is with electrics not plumbing. :-)) :-))
Title: Re: what have I done wrong ??
Post by: DickyD on June 28, 2012, 06:17:29 PM

Before you change anything, I would suggest you  put it in the bath with only a short bit of silicon tubing  connected to the pickup tube and hang it over the transom, rev up the motor and see if you get any flow of water.


You could do the same with the silicone tubing connected up Martin.
Title: Re: what have I done wrong ??
Post by: Stavros on June 28, 2012, 07:19:27 PM
One other thing you could do is as follows get a syringe and back fill the cooling tube with water so ther is water allready in the system,I have had this problem before and I cured it by doing this,es I know t is a paint in the derrier to do everytime BUT a lot easier then having to redrill everytime.You can do this in the bath to prove it works


Dave

PS glad to see from your other thread you had soldered the electrical crimps
Title: Re: what have I done wrong ??
Post by: CJ on June 28, 2012, 07:43:11 PM
There's an idea I hadn't thought of actually Dave....might load it and blow through in the bath, worth a try at least. And yeah, all soldered nice and tight  :-))
Title: Re: what have I done wrong ??
Post by: RAAArtyGunner on June 28, 2012, 10:04:08 PM
Nay Martin, that's a common sense approach  {-) You'll be telling us next that he could also fine tune the system to get maximum flow using the same method.  %%

     Regards   Ian

Ah Mayhem rules  :-)) :-)) %% %% {-) {-) {-)
Title: Re: what have I done wrong ??
Post by: CJ on June 29, 2012, 09:07:04 PM
OK Gents - HELP  >>:-(

Sorted the split, no difference, so popped the tube off and there was no pressure there at all, didn't even leak !!!

So.......Opened the end up, moved the inlet to the middle, and tried again....OK so water  spurts into hull, so reconnect tube and realign into the centre of the hull.

(http://s13.postimage.org/sm8s8mk9v/IMAG0184.jpg) (http://postimage.org/image/sm8s8mk9v/)

(http://s17.postimage.org/4cld1hmfv/IMAG0186.jpg) (http://postimage.org/image/4cld1hmfv/)

Now bath test and I have water "dribbling through" - now please laugh if you wish as I am no expert on water cooling !! But after 5 or so mins running in the bath holding her, motor smoked as per previous and got very flipping hot.

Now, did the water cooling not work as there was no flow of the hull through the water - and it is incorrect to hold the hull ?  I do know the answer to that one !! (doh) %% ? or was the dribble the best I am to expect ? In which case what am I doing wrong.

Nay Martin, that's a common sense approach  {-) You'll be telling us next that he could also fine tune the system to get maximum flow using the same method.  %%

     Regards   Ian

 Interested to see how I can get maximum flow fine tuning ??

I will try and test on the lake over the weekend but would be interested on what everyone's thoughts are !!

Cheers

CJ

Title: Re: what have I done wrong ??
Post by: Martin [Admin] on June 29, 2012, 09:30:03 PM
PM sent.....  :-)
Title: Re: what have I done wrong ??
Post by: funtimefrankie on June 30, 2012, 08:11:26 PM
I'd open up more of the tube facing the prop, more like a slot than a hole in the end.
Title: Re: what have I done wrong ??
Post by: Martin [Admin] on June 30, 2012, 09:28:42 PM
 :-))
Title: Re: what have I done wrong ??
Post by: nick_75au on July 01, 2012, 01:34:26 AM
I think you have a different problem, in that the prop is too big for that motor, that is why its getting hot.

Can anyone provide the specs of the Kestral IE rpm at 12 volts.

There are several options, reduce the voltage, use a smaller propeller, gear the motor, replace the motor with something that has a lower RPM at that voltage.

Cheers
Nick
Title: Re: what have I done wrong ??
Post by: DickyD on July 01, 2012, 02:53:17 AM
I think Nick is right.

I have had 2 of these boats and the props were definitely a much finer pitch and about 35mm diameter.

Kestral
[163]

High torque medium, speed motor with a low current consumption. Best use in fast, light, planing models such as M.G.B.s etc. Can be fitted to an Olympus belt drive for large heavy models such as Liberty ships, and Battleships.

Power range 4.8 to 12 volts
 

R.P.M @ 6v 5500   free running amps 3amp
Spec. 5 pole.
Title: Re: what have I done wrong ??
Post by: gwa84the2nd on July 01, 2012, 12:53:13 PM
also what is the bore of the tubing you are using if its snaderd fuel piping then i fined this to be to restrictive and personly use 3.2mm id or 4mm id from prestwich models

neer the bottom of the page

http://www.prestwich.ndirect.co.uk/hdwraccs.htm

Title: Re: what have I done wrong ??
Post by: CJ on July 01, 2012, 04:27:56 PM
Cheers chaps,

The silicone tube is standard (2.8mm "ish) so yeah can order some of that up, and can open up the inlet so more flow in.

Richard, I know you said before 35mm prop, on previous post.....the only one who did to be fair so will give that a try also as she is getting stupidly hot after 10 mins run time, I am sure that isn't helping matters but not strictly stopping the flow of water - or is it ??

CJ
Title: Re: what have I done wrong ??
Post by: essex2visuvesi on July 02, 2012, 06:01:09 AM
I have been having the same issues with my Huntsman i get some water flow but not enough... I ended up adding a screen washer pump into the cooling circut.  A 12V pump running at 4.8 V seems to give a nice flow.  The pump is then operated via a switch on the TX
Title: Re: what have I done wrong ??
Post by: CJ on July 02, 2012, 11:15:23 AM
mmmmm, cheers....now there is an idea I hadn't thought of, although not sure where I can mount or the weight involved...might be a last ditch attemp solution though that is worth a try, will try and bore out the intake, some larger i/d tube and a smaller prop first and see what happens. Can't quite work out what the issue is though  {:-{

CJ
Title: Re: what have I done wrong ??
Post by: Circlip on July 02, 2012, 03:26:50 PM
Perhaps it's an optical conclusion, but referring to your photos in post #16, the pickup tube seems to be too long and too far away from the prop. Back in the Diesel days, we had the hole in the pickup tube fully covered by the tip of the prop and a clearance of about 1/8" (3mm) between the tube and the rear face of the prop.

  Ref. to fine tuning was due to being able to see the output rate from the cooling outlet with the thing in the barf. Wersent possible wiv a diesel as Mummy used to get really annoyed with the brown ring round the inside of the bath.   :embarrassed:

   Regards   Ian.
Title: Re: what have I done wrong ??
Post by: CJ on July 02, 2012, 06:26:38 PM
Ian,

Cheers for that, yeah may have a point well made, tommorows job is to work on the pickup so will take that on board, am hoping new tubing will have arrived too with smaller blade that will assist the motor not getting so hot and also make the tip being more in line as suggested.

Will see how we get on !!

Cheers  :-))

CJ
Title: Re: what have I done wrong ??
Post by: CJ on July 16, 2012, 03:58:29 PM
Thank you Martin for the chat - everything taken on board, new inlet location, sharper angle on the inlet, thicker tubing and re-routed shorter and dumped in the bath for a splash....

(http://s7.postimage.org/mjqht8nfr/IMAG0193.jpg) (http://postimage.org/image/mjqht8nfr/)

(http://s9.postimage.org/r8hvo0qa3/IMAG0196.jpg) (http://postimage.org/image/r8hvo0qa3/)

I do seem to now have a steady flow through, also now running a 30mm X prop, once all this rain stops I will get her out on a run and see if she can keep her temperature down!!

Thanks all for the comments and help!

CJ


Title: Re: what have I done wrong ??
Post by: ACTion on July 16, 2012, 04:10:24 PM
CJ
That looks like a helluva big boat for such a small motor and prop. What's the model?
DM
Title: Re: what have I done wrong ??
Post by: CJ on July 16, 2012, 04:25:23 PM
Hi Dave,

It's a Robbe PT15 hull, http://www.modelboatmayhem.co.uk/forum/index.php?topic=37569.0

(http://s9.postimage.org/yvw1y7r4b/IMAG0176.jpg) (http://postimage.org/image/yvw1y7r4b/)

(http://s13.postimage.org/s1xucbkab/IMAG0177.jpg) (http://postimage.org/image/s1xucbkab/)

She's on a Deans Marine Kestral and 35mm X prop - not tested at the moment, she was running a 55mm X prop and was planning really nicely, unfortunately you couldn't touch her for upto 30 mins after - Just dabbling with a few things as the water cooling wasn't working, I am thinking I might replace the motor too as I think I may have cooked it  :embarrassed:

Why - any thoughts ??

CJ
Title: Re: what have I done wrong ??
Post by: Guy Bagley on July 16, 2012, 05:06:43 PM
bring her down to black park one sunday morning, we'll get to the bottom of this once an for all .....we can bring different props and see what effect that has to current draw
Title: Re: what have I done wrong ??
Post by: ACTion on July 16, 2012, 05:57:13 PM
Why - any thoughts ??
CJ

The usual reason for an overheating motor is either the wrong motor, the wrong prop, the wrong voltage - or perm any two and then add one for fun!
I can't find any current listing for the Robbe PT15 but it looks at least three feet long from your pictures. On a single prop I wouldn't run anything less than a Speed 700 in such a model. An X55 is altogether too much for any brushed motor on the sensible side of a Speed 900BB. I'm not surprised that the poor little Deans motor is getting worked up - it's like putting a 1400cc petrol engine into a quarry truck and then trying to drive it up a wall in fifth gear.
Unless you have a burning desire to go brushless then I would say to remove said Kestral, fit a Speed 700 9.6v motor (#G3308) and run something like a 40mm 3-blade brass prop.
Suit yourself, as someone once said.
DM
Title: Re: what have I done wrong ??
Post by: CJ on July 16, 2012, 07:00:04 PM
Thanks for the offer Guy, I might just do that very soon - haven't you got an event planned in September ??

I'm not surprised that the poor little Deans motor is getting worked up - it's like putting a 1400cc petrol engine into a quarry truck and then trying to drive it up a wall in fifth gear.

 :embarrassed: :embarrassed: Yeah OK, I get your point.....hey it's all trial and error. The parts was recommended elsewhere although I have mixed and matched and have to say not massively impressed with the Deans motor.

Another member has just mailed me the Speed 700 with a 40mm X prop setup so will try that  :-))
Hey - this is surely part of the fun, models are never finished are they  :}

Cheers

CJ
Title: Re: what have I done wrong ??
Post by: john44 on July 16, 2012, 08:24:44 PM
Hi guys, the PT15 is 34.5" long with a 9" beam.
I run mine using a car fan motor. It never gets hot.

john
Title: Re: what have I done wrong ??
Post by: Guy Bagley on July 16, 2012, 09:41:46 PM
Thanks for the offer Guy, I might just do that very soon - haven't you got an event planned in September ??




oh yes, all welcome -
Title: Re: what have I done wrong ??
Post by: CJ on July 17, 2012, 12:40:03 PM
I would say to remove said Kestral, fit a Speed 700 9.6v motor (#G3308)

Anybody any ideas where I might get one, seem to be unavailable everywhere - or an alternative suggestion Dave ??

Cheers

CJ
Title: Re: what have I done wrong ??
Post by: CJ on July 19, 2012, 11:04:48 PM
OK, so speed 700 unavailable everywhere  >:-o so gone for the Speed 600BB   %%

All water cooling work complete and new motor now fitted and she sounds nice, will try and get some testing done on Saturday with various props ready for the sun to shine all day on Sunday and get some proper playtime in  :-))

CJ
Title: Re: what have I done wrong ??
Post by: CJ on July 21, 2012, 12:51:18 PM
 >>:-( OK, so flippin water cooling still not working  >>:-( , I am thinking that whe is planing just too much to actually get any water through her !!

Either way it appears the new setup means it is not needed anyway, the new Graupner Speed 600BB and a 40mm X Prop means she goes like stink, planes at over two thirds and she still stays cool after a 30 min runtime - Will try and play a bit more as I hate the fact it's beaten me but will probably end up with the filler out  {:-{

(http://s14.postimage.org/71xzfs7pp/IMAG0197.jpg) (http://postimage.org/image/71xzfs7pp/)

CJ  :-))