Jet Drive

[egneg]

I may reconsider building one. Check this out.

http://www.hobbyking.com/hobbyking/s...dProduct=13388

[sundog]

Yeah, I've been salivating over this one for a while now. But it's in a whole different league as far as costs go ($$ jet drive, motor big enough to turn it, esc big enough to handle the strain, etc). Oh well, it's nice to window shop and dream.

[Andrewg]

Go to MHZ europe - the prices there for jet drives are far better than the hobbyking jet which is a clone of the Graupner so is tall heavy and has quite low efficiency

[sundog]

Go to MHZ europe - the prices there for jet drives are far better than the hobbyking jet which is a clone of the Graupner so is tall heavy and has quite low efficiency

No, they're not. I found this link http://www.mhz-powerboats.com/mhzpow...3a1358889e9948 to MHZ Europe which have only two offerings, a 49mm and a 53 mm. The 'Jet power 3' (53mm) looks more like the HK than the Graupner 2347 and costs 295 Euro ($412 today), and so is not "far better" in price. I don't know about the efficiency - where did you get your information? I believe it was MHZ that caused the stink about copy infringement on the HK offering that delayed manufacture for so long.

[old guy]

been watching these too but read what model12 said, there is a jet forum and we are waiting for some one to post how it is but no one has got one yet from the first order out ?
Rick

[rcjrboatman]

Here are some more jet drives that are reasonable. Very well made. http://www.jet-drive.de/index.php?op...id=4&Itemid=17

[mickieb49]

I will have to say after dealing with Graupner , Kehrer, and the bigger Swashdrive units that obviously the best is the swashdrive . For the smaller units , Kehrer has a better construction in the inlet and turn nozzel but the impeller and flow straightener setup could be better, the graupner unit would have been better if the inlet and turn nozzel were a better design, but the impeller /flow straightener setup worked ever so slightly better ( didn't unload so much).
Just my 2 cents anyway....
mick

[Andrewg]

link fr MHZ

http://www.mhz-engines.com/

Mickie you are dead right the swash is by far the best. Pity it is unobtainium.

The efficiency figures came from a Jet and Swash boards.

A coupleof years ago I did a Neu 2200- Castle Hydra - Swash unit. I did the power train research and the owner did the jet research. The model outperformed worked gas motors and had a 8-10 minute runtime.

Also I have a Graupner here now and frankly the quality is rubbish. The Hobby King is far better. The intake grill is plastic and easily broken likewise the nozzle controls are plastic and not particularly strong and the unit is tall and made taller in practice by the way the contol arms are located. Also the guidance provided with it makes for very busy and poor set of linkages to those controls. The rear bearing is hard to get to, an inherent design issue, and rusts quickly. Beware of this in the Hobby King unit.

The efficiency differences arise as the Swash has a true impellor which is CNC'd and the gap to the housing is tight. There was an article on Swash about its development. Which was done over several years and versions with a view to making significant improvements over the Graupner. On the various jet boat boards where there is some serious intent the concsensus was the MHZ unit bested the Graupner.

The Graupner was designed and produced in the early 90's for petrol motors which at that time were running at about 12000 rpm...., inlet has a high lift and the fan chamber/plenum is a very ordinary shape and finish. The smallish fan blade has very larger gaps to the housing,

The newer MHZ has a larger fan and a lower profile ie inherently more efficient propulsor and less distance for the water to be lifted. They bode well for its overall efficiency. It is alloy. The smaller unit has the same size fan as the Graupner and Hobbyking. As I am using an $AU, the MHZ's smaller impellor unit - same as the Chinese version - is cheaper for me.

[Punisher 67]

Just chiming in.........................

[sundog]

AndrewG, I believe you might be mistaken. You wrote "the smaller (Mhz) unit has the same size fan as the Graupner and Hobbyking". But the HK unit has a 53mm impeller - same as the larger of the two Mhz units (Graupner is 49mm). And maybe we shouldn't compare to jet drives (Swash) that are no longer manufactured or available for use (yes, I know the HK unit is on backorder). I would like to see that data on comparison of efficiencies of drives if you ever come by it again.

[oscarel]

Here are some more jet drives that are reasonable. Very well made. http://www.jet-drive.de/index.php?op...id=4&Itemid=17

Here's a site in the US that also may have the KMB jets, http://nwnitrorchobbies.com/

[oscarel]

Here's a site in the US that also may have the KMB jets, http://nwnitrorchobbies.com/

And here's one of the 28mm's they have on ebay http://cgi.ebay.com/Kmb-28mm-Jet-Dri...item3365aa94ad

[mickieb49]

link fr MHZ

http://www.mhz-engines.com/

Mickie you are dead right the swash is by far the best. Pity it is unobtainium.

The efficiency figures came from a Jet and Swash boards.

A coupleof years ago I did a Neu 2200- Castle Hydra - Swash unit. I did the power train research and the owner did the jet research. The model outperformed worked gas motors and had a 8-10 minute runtime.

Also I have a Graupner here now and frankly the quality is rubbish. The Hobby King is far better. The intake grill is plastic and easily broken likewise the nozzle controls are plastic and not particularly strong and the unit is tall and made taller in practice by the way the contol arms are located. Also the guidance provided with it makes for very busy and poor set of linkages to those controls. The rear bearing is hard to get to, an inherent design issue, and rusts quickly. Beware of this in the Hobby King unit.

The efficiency differences arise as the Swash has a true impellor which is CNC'd and the gap to the housing is tight. There was an article on Swash about its development. Which was done over several years and versions with a view to making significant improvements over the Graupner. On the various jet boat boards where there is some serious intent the concsensus was the MHZ unit bested the Graupner.

The Graupner was designed and produced in the early 90's for petrol motors which at that time were running at about 12000 rpm...., inlet has a high lift and the fan chamber/plenum is a very ordinary shape and finish. The smallish fan blade has very larger gaps to the housing,

The newer MHZ has a larger fan and a lower profile ie inherently more efficient propulsor and less distance for the water to be lifted. They bode well for its overall efficiency. It is alloy. The smaller unit has the same size fan as the Graupner and Hobbyking. As I am using an $AU, the MHZ's smaller impellor unit - same as the Chinese version - is cheaper for me.

I Tend to agree, the graupner units are pretty much rubish, and when you want to put some more power thru them they basically do not cope. If you do want to use one i would recommend to put a layup of glass around the inlet, so the seem won't burst.
Can't say i know too much about the MHZ ones as i have never set my eyes upon one, i own 2 swashdrives, both the stainless and the mk2 versions and they work very well. Very interesting to see a brushless version go.
The kehrer units appear well built but you will need to improve the flow straightener and the impeller (more blade overlap) to get them working efficiently, they seem to unprime a little in the corners where the swashdrives don't.
Here is the link to a sprint i have just finished:
http://forums.offshoreelectrics.com/...ad.php?t=22122

Regards Mick

[old guy]

Mick if you ever want to sell a swashdrive I'm just a email away lol I have the MHZ its not bad but no swashdrives
Rick

[Andrewg]

There are three videos of the brushless Swashdrive on youtube:

SwashDrive hull (custom cf sandwich and cut down profile) and pump, Neu motor, TP 10S pack - runtime works out at up to 8 min but 6-ish if it is driven hard and tight.

http://www.youtube.com/user/j73ish#p/a/u/0/lox4v5ky9xQ

The owner of the SD he is now doing a small Keher based too.