mickieb49

Windsurfing eh Grael? gotta say i share your interest there too mate, will certainly keep you fit. Keep up the jet unit making , i was thinking along the lines of getting a 3d printer to make mine???? jut not sure the ABSwill be strong enough?


Was going to say if anyone needed a hull PM me , their $100 AUD +postage to whatever country. The pictures of them is in my previous post
Cheers Mick

grael

I used to live 5 minutes frm the beach WITH my gear slung under my arms, and pick up all the best southerlies from the cook straight, now I'm close to a different beach.

About the 3D printing, I started a project: minifactory: Back again. , but need to put some more time in to get it running properly. I researched the "Reprap" project, but decided the chips being used were too slow and not the right sort, so I did my own design with an Arm Cortex M3. I may redo the output stage though, simplify it and use built in electronic protection.

Agree, ABS as printed may not be strong enough. Same volume injection moulded would be much stronger.

I'm looking more at it as an intermediate stage, to print moulds to make sand cores to metal cast, or models to mould silicon over in preparation for a polyurethane plastic pour.

mickieb49

The prototyping idea was what i was thinking too, especially the impeller and the stator, these are just a little hard to make by hand properly , i was even thinking of the silicone molds and injection molten ABS ??? just trying to find a silicone that has high enough temp resistance as well as tear resistence. Shame thing is that all Silicones are expensive.....
Mick

grael

I use mostly "banaskin" solicone and "easycast" 2-part polyurethane resin for my final plastic. http://www.topmark.co.nz/

One of the other guys on here was doing a fine job making impellers with a special jig he's made, I think he had some downpipe with angles cut into the end for pitch, and a speed tool that was limited in travel for any degree rotation by the edge of the downpipe as the raw part and downpipe were rotated. They looked pretty good anyway. Using a hex spanner, I think he could cut 2, 3 and six blade impellers.

mickieb49

Wow !, have you got any pictures of this? seems like an easier way to make them. Afterall there is more than one way to skin a cat!
Thanks for the link, interesting stuff, maybe i can try to find a supplier in Aust.
Mick

grael

Try the middle of page 163,
and this for one that I made, running:
[youtube]http://www.youtube.com/watch?v=rEj1ainByTs[/youtube]

mickieb49

Very intersting Grael, do you use a syringe to inject the resin? i was thinking on building a fairly crude pressurised melting pot for ABS to inject directly into the silicone molds, something similar to the wax pots for investment casting , It's just thought anyway?
Mick

leebart121

I would like to know if anyone knows were to find a cnc program for making a jet drive out of aluminum. I have seen some made in another thread that were machined on a cnc machine and would like to know if anyone here would like to share the program or knows were to get a copy of a cnc program so that I could make one for my 48" mono.

grael

No, most plastics, even friendly plastic/polymorph plastic which melts at around 73 deg C, are very viscous and require very high pressure injection to fill the mould. Even the hard grades of silicon are unacceptable for moulds.

Two part Polyurethane resin can be poured while still in the low viscosity state, some of the mixes are less viscous than others, and heat will also reduce viscosity. It's good, however to briefly vacuum before pouring.

Set up your mould like a metal casting mould, add a sprue with a funnel shape on top, connecting under your model for filling, and risers (tooth picks work fine) for air to escape. I find birthday candles work well for sprues, with tea light candles for funnels. If using wax for your model, let the mould set for the rated time at ambient temperature, too much heat will make the wax sweat and deform.

sundogz

Turns out R/C Planet has the PRB3565 replacement Duck decoy drives for $16.95 each, so I got two of them. Cute little things. They come equipped with a water pickup and decent grate (also a piece of screen) and mounting hardware. It has a 15mm impeller and a 3mm shaft! I'm sure a 2mm shaft would have been adequate. I'll be putting one of these into the boat ISIRC10 designed and built. This would be a good drive for the Pushball boats as well. I'll post the build once I get it going.

damfurst

Looks good sundogz. One thing that can to be done to improve the water flow for cooling is to drill out the tube on the stator. Doing this made the stream go from a dribble to a good strong stream. Look forward to the builds.

grael

Very nice price sundogz !
What size boat are you going to put them in ?

If it's a small, narrow boat, then I suggest an inrunner, because I've had bad experiences on that sort of setup, with an outrunner corkscrewing the boat every time it went airborne.

Quicksilver

Wow, you guys have some projects going. Just wanted to say hello, the jet villain is still sitting in slings on my wall. This spring I plan on getting both boats going, my 2 yr old would love them. I've got to go through the 50 pages or so that I missed on here.

sundogz

I'm going to put one in that wooden boat that ISRC10 built and sent me a year ago. It should fit it quite nicely. Thanks for the reminder, yes an inrunner will be best.

Quicksilver, it's nice to hear that you're still floating around these parts. Has it been two years already? Well, better get to reading - there's quite a load of info here to absorb!

doug702

My Feedback: (1)

i have for the last 2 weeks been trying to find a jet drive that will hold up to a nitro motor but all the places ihave look are out of stock does anyone know where i can get one that has it in stock something like the 29 mm graupner would be nice

sundogz

KMB has 10) 28mm and 6) 33mm jet drives in stock according to their [link=http://www.jet-drive.de/index.php?option=com_virtuemart&page=shop.browse&category_id=2&Itemid=17]website[/link].

doug702

My Feedback: (1)

thanks i have not heard of kmb are they good drives?

doug702

My Feedback: (1)

the kmb drives i saw are recomended for electric motors i am looking for something i can use nitro motor with

sundogz

The Graupner model 2347 is recommended for internal combustion engines. You can check them out [link=http://www.cornwallmodelboats.co.uk/acatalog/graupner_jet.html]here[/link]. Don't know if they have it in stock - you'll have to check with them. It is much larger at 49mm impeller.

Edit: I now see they don't have them in stock at this time. Sorry.

sundogz

Are you sure the KMB are not suitable for nitro? [link=http://cgi.ebay.com/Kmb-28mm-Jet-Drive-Boat-Nitro-Gas-Electric-Fast-Fun-/220744807185?pt=Radio_Control_Parts_Accessories&hash=item33656a7311]This ad[/link] says "Nitro Gas Electric". You need to check further.

doug702

My Feedback: (1)

thanks sundogz i will check it out but yeah im pretty sure kmb says electric is it i imagine because of the rpms a nitro will turn

mickieb49

Well got the Hulk out today and here is the result: \
http://www.youtube.com/watch?v=gbh2X8XVt5g

Before the video was taken , it spat the original flow straightener out the back , so i had to make another, not too sure it is helping but ???? The jet is also unloading during some courners , i am thinking i could also be a problem with the impeller? This is a Kehrer 28mm unit and i was initially impressed with the whole construction but now , i am not so sure ? I think the Graupner units may work just a tad better ??? but this is also subjective, i may have a bad taste in my mouth from the straightener spitting out the back before i had a deascent play .
Mick

sundogz

Looks like you did good with the stator, and could use a ride plate or trim tabs. My Tear-Into is porpoising like that at high speed and I'm making a ride plate for it. That ought to fix it. Good job.

mickieb49

Yeah i was thinking on something like that, or convert the steering nozel over to a trimable one ?  Just want to sort out the unloading problem first, may make another impeller that has blade overlap .
Mick

leebart121

Would this work with a gas engine? like a weed eater that is un-moded? and push a 48" wood boat?