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Author Topic: Water Jet experiment and Jet boat build  (Read 21757 times)

Circlip

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Re: Water Jet experiment and Jet boat build
« Reply #50 on: March 30, 2012, 01:41:00 PM »

White or pale yellow are easier to see submerged  :-)) %)

  Regards   Ian.
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Mad_Mike

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Re: Water Jet experiment and Jet boat build
« Reply #51 on: March 30, 2012, 03:05:22 PM »

very funny   <*<
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Netleyned

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Re: Water Jet experiment and Jet boat build
« Reply #52 on: March 30, 2012, 04:06:40 PM »

Have you thought of a name yet?

Gazunder sounds good  %% %% %%

Only joking Mike


Ned
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Mad_Mike

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Re: Water Jet experiment and Jet boat build
« Reply #53 on: March 30, 2012, 04:38:53 PM »

what makes you all think its gonna sink >>:-(
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Circlip

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Re: Water Jet experiment and Jet boat build
« Reply #54 on: March 30, 2012, 08:28:11 PM »

Not thinking about it sinking, just the sheer power from the waterjet driving it under.

  Regards   Ian.
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Mad_Mike

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Re: Water Jet experiment and Jet boat build
« Reply #55 on: March 31, 2012, 07:58:01 AM »

funny how at the beggining  of this thread people were doubtful that the jet would produce any thrust at all %) I dont think it will drive it under, im fitting strakes to it at the minute. Ive dicided to go with mettalic blue. ill put some go faster stripes on it too, just in case its slow.
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Circlip

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Re: Water Jet experiment and Jet boat build
« Reply #56 on: March 31, 2012, 11:14:11 AM »

Quote
funny how at the beggining  of this thread people were doubtful that the jet would produce any thrust at all

  Not everybody, some of us remember the Hoover "Senior" (Cast case one, not the plastic version.) O0

  Lots of years ago, when electric powered "Kipper boxes" had just been invented, a demo at one clubs open day saw a very effective submarine every time he opened the throttle. {-)

   Regards  Ian.
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Mad_Mike

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Re: Water Jet experiment and Jet boat build
« Reply #57 on: March 31, 2012, 12:01:13 PM »

why did it submarine?
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Circlip

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Re: Water Jet experiment and Jet boat build
« Reply #58 on: March 31, 2012, 01:36:04 PM »

Combination of pointy nose, heavy batterypack for size of hull (Note I said early, lots of "C" sized cells soldered together) and prop trim a bit orft. It bounced when power was applied and on landing, the pointy bit dug in before the guider reacted. Bit like a bouncy landing but substitute the grass for water.

  Regards  Ian.
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Mad_Mike

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Re: Water Jet experiment and Jet boat build
« Reply #59 on: April 03, 2012, 12:33:06 AM »

been a while so heres an update.

First up i wanted some drivers and so i flicked threw ebay and managed to find these guys:

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=160776307985

I figured that the scale is about 1/10th of the boat and two of these vacuum formed racing drivers will do just the trick. Firstly i cut off the plastic edges then on one of them hacked off his arms!



I only need one driver of course so a little bit of work was required. After hacking off his arms i used my lighter to warm up and bend the plastic to follow the new pose of the co driver if you like. I then used the pieces of plastic that i cut off to fill in the gaps around the side and between the arms off the co driver, i reckoned matt red would do just fine for their suits. Ive also been painting the boat itself. I went in the end for metallic blue which i suppose i allways had the intention of doing anyway. I suck at painting so dont expect Leonardo Da Vinci brushwork or you will be disappointed:



the drivers are just positioned temporarily for the camera shot.

Ive also plumbed in water cooling for the esc:




the ESC is from giantcod and a budget one to say the least, forward only it is however pretty good. Being of oriental origin i went over kill on the amp rating just in case:

http://www.giantcod.co.uk/80amp-boat-p-404814.html

The motor doesn't draw anywhere near that kind of current, for 13 quid though i cant complain. I dont even think it was necessary to watercool it but i did anyway simply because you never know. The water picks up from inside the nozzle by a small piece of brass pipe with a 45deg chamfered end. i tested the system once plumbed in and it makes a nice slow but affective trickle. Just the job :-))

On the other hand however Ive got a problem.  {:-{ the bush which the motor spindle goes through into the pump housing leaks. Only when the motor is turning though. I thought i had cured it buy putting a large diameter washer between the impeller and the bottom end plate of the pump housing, then packing it with grease. It hasn't worked so i need to do some rethinking, I have a 3.17mm wide motor axle which i will exchange for the standard shorter axle. With the motor spindle extended going through a snug fitting brass tube and the motor sitting higher I hope it will cure it. hopefully {:-{

oh by the way the steering nozzle works magic and straightened out the jet stream perfectly. I turned the nozzle starboard to counter the effects of the GP which i had previously anticipated to be a problem, I tested it in the domestic tank and the boat turned to starboard rather that port like it did in the youtube clip. I backed off the bit of right hand until it ran straight, funnily enough the steering nozzle was centre again. Therefore the the original problem of turning wasn't down to the motor torque but because the water jet was coming out at an angle.

So there you go :}
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Mad_Mike

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Re: Water Jet experiment and Jet boat build
« Reply #60 on: April 04, 2012, 11:21:07 PM »

I managed to gain some control of the leaking bush by exchanging the standard motor shaft for a long one and running to through about 12mm of brass tube:



Its not completely dry though and a little water does seep through into the motor but it doesn't seem to be having any detrimental effects. I hope that once the boat is water born and planing that the issue will be lessened.

Ive painted me crew too:



theyl do  :-))
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Mad_Mike

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Re: Water Jet experiment and Jet boat build
« Reply #61 on: April 06, 2012, 04:23:15 PM »

Ok so ive just about completed the deck features. first up a roll bar:

The roll bar is made from plastrut. I was dead set on having the corners rounded rather than mitred at 90 deg so i had to come up with a plan. In order to bend the plastic i had to heat it and bend it without it kinking so to overcome this i decided to insert a peice of wire or something in side the tube to stop it going flat. I gathered various tubes and wires at first including a bike lock cable. The original tube splintered when melted and the bike lock cable was an absolute ***** to cut. I settled on using curtain wire and plastrut tube in the end and the wire fitted in the end perfectly:



I stripped the plastic off the curtain wire to reveal the coil:



I reckon that this curtain wire will make a good flexicable for something, it was only 57p too:



Anyway i marked off where i wanted the bend in the tube and inserted the cable into the pipe:



I heated the tube gently with my lighter then bent the tube with the wire inside, I let the tube cool off then pulled the wire out of the end:



I think the result is pretty good altough the diameter does shrink a bit, but then i suppose if you were to bend steel tube in a pipe bender it would do the same thing. To be honest this is probably my third attempt as on previous attempts i got the plastic too hot and the end results were awful. Anyway after a bit of fiddling with the file i fixed the roll cage to the deck:



Ive also made an engine out of plasticard, the exhaust pipes are pen tubes:



Ive also adapted the air filter into a lock nut to keep the deck down. I epoxied a nut inside a tooth paste tube cap then added 2 circles on the top and bottom of the cap to male an airfilter. Ive screwed an eye in to the bottom of the hull then a threaded bar with a hook on the end hooks into the eye comes up threw the centre of the engine. The air filter screws on top of that too hold the deck down securely:



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Netleyned

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Re: Water Jet experiment and Jet boat build
« Reply #62 on: April 06, 2012, 04:49:11 PM »

Very neat setup there Mike
When is the launch day?

Ned
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Mad_Mike

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Re: Water Jet experiment and Jet boat build
« Reply #63 on: April 06, 2012, 05:46:36 PM »

god knows the kids are off school for easter and cant handle them all and sail the boats at the same time. I need to get the painting done but it wont be long till im finished now. Im not going to great lengths into the details on this build.
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Mad_Mike

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Re: Water Jet experiment and Jet boat build
« Reply #64 on: April 08, 2012, 08:49:08 PM »

right i reckon im about done, painted it up and made some numbers out of wheely bin stickers, ill need to make a grill for the water inlet to stop stuff going in the pump. I cant tell you when ill get it on the lake though i hope thursday.  :-))




can anyone tell me if its totally necessary for my 2.4ghz antena wire to be stuck out the top of the boat?
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Danny

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Re: Water Jet experiment and Jet boat build
« Reply #65 on: April 08, 2012, 10:40:40 PM »

Mike - as long as there is no metal or carbon fibre surrounding the aerial, it will work fine within the boat.  2.4GHz goes straight through grp or wood.
Cheers
Danny

gwa84the2nd

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Re: Water Jet experiment and Jet boat build
« Reply #66 on: April 08, 2012, 10:45:46 PM »

i run mine onn my ic boats inside the radio box so you shouldent have a problem runing with the airial below deck  :-))
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Mad_Mike

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Re: Water Jet experiment and Jet boat build
« Reply #67 on: April 08, 2012, 11:08:38 PM »

good ill do that :-))
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hopeitfloats

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Re: Water Jet experiment and Jet boat build
« Reply #68 on: April 13, 2012, 10:21:37 AM »

so no test run thursday :-)
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Mad_Mike

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Re: Water Jet experiment and Jet boat build
« Reply #69 on: April 13, 2012, 11:40:37 AM »

yes but it wasnt good. I started off the test run with a partially charged testing lipo, everything seemed ok, went straight as an arrow too. Thought right lets give it some welly then so i put in a fresh fully charged lipo and it launched like a scolded cat, came to some ripples in the lake about 20ft out and got it airbourne, on landing the boat cut out completely. I sent me rescue boat after it to recover it and discovered the 25a fuse had popped, bath testing showed that the continuous running was around 7 amps so i thought 25 was plenty of head room especially will the esc rated at 80amp continuous. Tried a new 30a fuse in it when i got home, forgot to take spare with me didnt I, power came back on servo and radio works but motor doesnt run. I reckon that when the boat went airborne the motor overreved when it went dry, then on contact with the lake the flooding of water in the pump loaded the motor again, spiked the current and popped the fuse. i need to purchase a better esc before i take it out again. I new it was risky buying the cheap oriental esc so i made sure i went over the top with its handling capacity, looks like it didnt work.  {:-{
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hopeitfloats

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Re: Water Jet experiment and Jet boat build
« Reply #70 on: April 13, 2012, 11:44:22 AM »

darn. does the motor turn. just a silly thought that one of the blades might have come off the impellor and jammed.  good to hear it is a runner though.
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TailUK

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Re: Water Jet experiment and Jet boat build
« Reply #71 on: April 13, 2012, 12:24:43 PM »

So plenty of "ooomph" then?  I've been watching the thread with interest as I think it could be used to power a model I have in mind.  My thought is to use two pumps, one left hand and one right hand, to counteract the torque problem. I'd pump into a chamber and use small nozzles off that.
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Mad_Mike

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Re: Water Jet experiment and Jet boat build
« Reply #72 on: April 13, 2012, 12:53:19 PM »

plenty of oomph, scale speed maybe a tad over, better tooling and more maths involved could see it perform much more efficiently but thats over my head. When i ran the boat their wasnt a torque problem, or at least not one i noticed. like i said it went straight, what i thought was torque making it steer was actually because the jet of water was exiting sqaure to the transom. The steering nozzle corrected that. Ideally two pumps counter rotating would eliminate any kind of gyroscopic precession as ive been informed its called.
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Krishna

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Re: Water Jet experiment and Jet boat build
« Reply #73 on: April 17, 2012, 10:03:29 PM »

great craft.. :-))
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Mad_Mike

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Re: Water Jet experiment and Jet boat build
« Reply #74 on: April 19, 2012, 10:21:49 PM »

The other day i was reading about timing and pwm settings for speed controllers. Thought hmm i wonder. On intial set up i programmed the esc so that the timing was 30deg and the pwm was 16khz. thats what the intructions said for driving outrunners. Took its word for it and set it like that. Of course on the original trial, it popped the fuse. After a bit of research I changed the timing to 15 deg with 8khz pwm and installed a slightly higer 30a fuse.

Managed to get a 3 minute run today, until it made a horrible shuddering grinding sounding and stopped again. Brought the boat back smoke was pooring out of the hatch compartment, Im not sure if i had fried the esc, the motor or both, they both stank pretty bad. The impeller was fine though so no jamming had occured.

the motor is a 2212-06 28a 2200kv with a 28mm dia case turning a 5 balde 33mm dia impeller:



i thought this motor would easily have enough torque to spin this impeller but it seems its drawing over the max rated current. There may be some  binding in the prop tube i made but i can easily sort that. Ive actually busted the original motor mount trying to get this out so ill need to make another anyway. I need to get the amps down and i reckon either a lower kv motor or a larger diameter one. With the motor as it is the rpm slows down when the pump starts to move water, if i get a lower kv it will obviosuly have less rpm per volt but im hoping the additonal torque of the lower kv motor will make up the differences in loaded speed between the 2 motors. back to the drawing board then.
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