jetboata

ok thanks for the help guys. will probably go with dragonfires idea of bolts on the top and screw in (carefully) the bottom holes. also im planning on running a mystery 5000kv outrunner on 2s and was wondering if anyone had any ideas on how to water or air cool the out runner motor.(sorry if someone has already asked this on here but there is a lot of pages on here now,94 now lol)

btw the motor is 25A max, pretty pathetic i suppose but would this have enough speed and torque to turn things along at a pretty decent speed?

sorry bout all the edits.

headhunter23

Give it a try but it might be a little hot, I have this vague memory of someone trying 4900rpm/kv and burned up motor. You have a tool to see how many amps motor is pulling? Might be helpful, for out runner, only two ways to cool, attach a fan either to the motor itself or a secondary cpu cooling fan(small) and run off esc. Or add a cooling plate between motor and motor mount, I've done this by making kind of a heat sink, essentially I had an aluminum plate before the intake of the jet itself and bent it up to sandwich between motor and mount.

Ivan.

damfurst

Hey Jetboata, I was noticing your motor mount & thought that maybe you could either drill one or two holes through mount and then push a brass tube through to attach cooling to. Or maybe make a one or two coil cooling coil around your mount. Either way a fan on the back side of the motor would probably be wise also as headhunter talked about. I've seen the fans on different websites but can't remember where now. I also remember somewhere in this thread that it was determined that 3200-3600 rpm/kv would max out this size drive.

Did you make your own motor mount/adaptor? How thick is the aluminum? Good luck!

DRAGONFIRE81M

man i missed alot lastnight . btw that motor adapter looks sweet if you did make it your self good job and i would try to make one withsome cooling like a water cooled head on a nitro motor . wouldnt be to hard if you have a mill . also that was mkmotorsport that had the 4900kv 20mm inrunner cooked both the motor and 25a mumba esc i thank he was running it on 11.1v when it happend . if you go with that 5000kv stay with a 2s . i got use the screws that come with the mini jet drives i use eather a 2-2.5 mm alean head bolt and then i make sure that i get a good coat of epoxy on the inside around the duct

Quicksilver

speaking of cooling, anyone ever think of making a heat sink that is part of the hull? In a real boat something like this would be called a keel cooler. Basically, take that outrunner and imagine the adapter attached to a plate on the hull similar to the one I had on the villain. That would cool the motor pretty well, probably better than any "normal" cooling method.

DRAGONFIRE81M

yeah qiuck i thank headhunter was talking about that

grael

Dragonfire,
re madmax's cooked brushless controller and motor, a couple of things could have happened:
1: Motor winding developed short and took out ESC MOSFET.
2: ESC MOSFET shorted, and overdrived a coil.

Same result, either way, but different cause.

Quicksilver,
yes, I think I mentioned it to the forum a page or two back, When I was a teenager my Dad was ordering a customised Jetboat for the nature reserve he was ranger for, on an Island. There was discussion of a heat exchanger going in, and I argued, and suggested for an aliminium pipe to be welded on the inside of the aluminium hull, to run the coolant through. It didn't happen ! Kind of nutty to go with boating traditions when you have a whole boat made of aluminium begging to be used as a heatsink ! I agree with you though.
Best way for us is to place an L section during fibreglassing of the hull, and sitting on the flat leading in to the jet intake. Then, pre drill for motor mount and shaft as well. Or, if you get your boats pre made, you can find your own solution. Short fins in the vicinity of the motor will reduce drifting in turns, but might make the boat more prone to roll over the moment you take finger off throttle in a high speed turn. Years ago, I tried two fins just back from the centre of gravity, mounted at the sides and curved in. Wickedly tight turns, but that wasn't a jet drive. Those weren't for cooling though.

jetboata

thanks for input guys. yeah i was thinking of drilling some holes in it and adding a cooling pipe to the motor mount. the way the back of the motor housing is shaped it sort of acts like a fan and sucks air into the motor.

dragonfire: i have no experiance with nitro motors so would you be able to find a photo or explain how the nitro cooling heads work please?

the motor mount is a piece of 36mm diam. aluminium that i machine up to be accurate to 0.1mm, with a small lip on the front that sits nicely in the small lip the mini jet motor mount has, the pictures will explain the rest.

i hope this motor doesnt burn up because when i got it the original shaft it came with form the factory was off centre so i had to machine myself a new shaft and made it 3mm thick the whole way.

another question; do any of you know if the purple motor shown would be better. its a 2600kv inrunner but i have got a clue on brand or max amp draw, not to mention that ive cooked 2 or 3 30A ESC's with this motor(running a surface piercing prop,2S lipo, flex shaft and 32mm prop in the yellow boat shown). so any help there would be appreciated too as i dont think i have a tool to read amp draw and i dont know how to read amp draw(egutting what probe where) or what tool to use.

heres a link to a video of some overseas fellas running a boat practically the same as the yellow one of mine [link]http://www.youtube.com/watch?v=QyYsNuhUeIs[/link]

Quicksilver

[sm=tongue_smile.gif] lol, He did just say that, didn't he. One of those need to read all of the replies moment. That's exactly what I meant.

DRAGONFIRE81M

yeah man here you go just so happens i have both .18 and .21 heads

grael

I'm starting on building my own reprap machine
http://dev.www.reprap.org/bin/view/Main/WebHome

End result, after a lot of hard work first, will be that I can use CAD to design my jet units or other parts, then print them or moulds for them in plastic. Once I have my CAD shape, I can test, tweak the CAD, re print a new 3-D working model, etc until I get it right.

Metal casting 2007, fast jet boat 2008, Feeling good to have big plans for 2009 !

jetboata

great thanks Dragonfire i think i will actually do that

DRAGONFIRE81M

anytime ...

Madmax160764

Water cooling motor mount...Under $30 http://cgi.ebay.ca/alumium-water-coo...742.m153.l1262

damfurst

They also make one for 380-400 size motors
[link]http://cgi.ebay.com/alumium-water-cooled-motor-mount-for-380-motor-rc-boat_W0QQitemZ290250353500QQcmdZViewItemQQptZRadio _Control_Vehicles?_trksid=p3286.m20.l1116[/link]

headhunter23

madmax that is a very nice lookin mount... spensive though.

jetboata

damn that is a nice mount mount thanks madmax, not sure what ill try and build now. im not too sure if the out runner i have is going to work it does get quite warm in the "tub test" ive just done, although i havent watercooled it yet. so does anyone have any suggestions for an inrunner 3600kv-5000kv motors that are avaliable in NZ for upto about $150NZ, that would work well in the jet sprint?

thanks

jetboata

sorry bout all the questions, "how do i tap the stator for watercooling? and can i still tap the stator and use the reverse bucket on the jet sprint, or do i need do have a pickup under the hull if i want to use the reverse bucket?

sorry about edit.

thanks

grael

Hi jetboata,
Most of us do tap into the outlet for water cooling pressure.

Theoretically, if you tap in where the nozzle is reducing in diameter, the pressure is actually low, rather than high, and I have had the experience of trying this once, and finding that I had no flow. However, if you protrude the pickup tube very slightly, and angle the hole so that it starts from behind, and is drilled forwards as well as to the centre, then you will get really good flow.
(Only protrude the edge of the pickup tube, not the whole end though)

Just remember, if one of your stator-outlet water paths gets blocked, and it's the same one as you have your water pickup in, then you will lose pressure. I've had this happen once with the one shown in the attached picture:

And another couple of pictures:

grael

Arrrrrgh !
I have found somebody else using my boat shape !!!

The Mokai:
http://au.youtube.com/watch?v=98yzDuNZqjk

Still, seeing as I designed up my hull about 15 years ago, I suspect they independently re-invented the shape.
Now I think about it, I think I'd seen the shape on amphibious planes anyway, and forgot the source myself

jetboata

hi grael

thanks for help, that Mokai's a pretty cool sort of a jet boat. you have sort of explained how to do it and my question should have been "how do i tap the nozzle" more than "can i" so i will edit that now, sorry for confusion.

thanks.

headhunter23

Here's basic idea.

http://www.jet-drive.de/cms/content/view/41/25/lang,en/

Ivan.

grael

Thanks for the link Headhunter,
Only thing I would note, is that you will get plenty of cooling like that, but no need to chamfer (remove the edge) the inside of the tube. Better to file around the outside to make it sharp, what you really want to avoid, is objects finding their way into the tube and then getting stuck, so it's best to have a the smallest part of the tube right at the entry.

Have spent an EXTREMELY frustrating day today.[&:] [:'(]

Got an email about activity in a build thread started by one of the moderators, only he deleted one of my posts to his thread, without telling me why, about a month back. [X(] Yesterday it started off again, and I posted [unsubscribe thread], as I am not interested in a topic that heavily censored. Finally found out today, that there is an unsubscribe button on each thread, quite close to the top of the page. [8D]

Then, I took my fast boat and the new, slow boat to the lagoon.
My boat developed a servo fault with the steering almost straight away. Ran the other boat, only it would not respond to the transmitter.
Took them home, fixed the servo problem on my one, and back down to the lagoon. Wouldn't start !!!
Took it back home, and finally traced it to a glow plug problem. Seems like something I put in to lube the engine while I wasn't running it has upset the platinum catalyst on my plugs. I think I tried some silicone oil. On the + side, compression is awesome. That, meaning in practice, that even with my 24 volt powered electric starter, it's really hard going without first loosening off the plug a few turns.

So, I changed plugs, to my high nitro plug, which was OK, but it's really fussy, needs a very hot combustion to run reliably off the battery. Lower resistance coil though, so even with a decent supply of charged AA NiMh cells, I was flattening them unexpectedly fast.

I also tried cooking my previously working plugs with a burner, still glow fine, but no improvement in behaviour on the engine head.

Looks like I need a new set of plugs [&o]

I guess you guys having an icy winter season aren't particularly bothered by my troubles !

It's my summer though, so I'd better sort it out...

grael

Has anybody run their RC Jet boats on a purpose built course ?

Here's a full size boat course here in New Zealand, with some races, to show you what I mean:
http://www.youtube.com/watch?v=X2Iyw...08CEFC&index=2

DRAGONFIRE81M

well guys i have a winter project just picked up a aquajet gp hull from ebay . any ideas on setting this one up im open to anything i have a new 29mm drive that im going to make some molds of and i have some 19mm drives just need to make an intach . im kinda leaning to a brushless . since i have nitro powered . so let the ideas fly