Graupner Mini Hydro

[Chop]

I have a Graupner mini hydro (16” long, 8” beam) that I want to put a slightly bigger motor into. It is a brushed system with a Graupner Speed 400 in it. I have a 3S, 1100mah battery and an Electrifly C-35 Mini ESC (6 – 12 NiCD/NH, 2S – 4S Lipo 5v/1.5 BEC).

Will the Graupner 480bb Race 7.2 (http://www.offshoreelectrics.com/pro...?prod=grp-6327) work well in this application? With the 400 in it, it handles very well. I let my 11 year old run it when I’m playing with other boats.

What other (reasonably priced) options would you suggest?

[Dr. Jet]

The Graupner Speed 400 6V motor has a Kv of about 2675 rpm/V and usually runs on about 10 to 15 amps maximum. That is why I have chosen to run similar setups in my 15" micros with the Chinese outrunner that has a Kv of 3000 rpm/V. The performance is about the same or a bit better than the Speed 400 on 2S, probably due to the increased efficiency and the slightly higher Kv and Kt of the brushless outrunner. This motor/ESC combo can be had for under $25 on ebay. It is a screaming deal, plus it is a bolt in replacement with no modifications required (other than allowing room for the spinning can of the outrunner). If you want to run 3S, I would recommend a lower Kv, maybe around 2500~2600 rpm/V. The 3000 rpm/V motor is best suited for 2S or 6 to 7 round cells. The Speed 480 motor has a reputation of eating brushes faster than the Speed 400 motors.

[Chop]

Thanks Dr. J.

Is there a brushless alternative?

[Dr. Jet]

The $25 brushless outrunner/ESC combo from ebay. It is a drop-in replacement for most Speed 400 applications. Slightly more rpm, slightly more torque.

[Chop]

The $25 brushless outrunner/ESC combo from ebay. It is a drop-in replacement for most Speed 400 applications. Slightly more rpm, slightly more torque.

I will give that a try, thanks for the info.

[Ocean Racer]

did you find the motor combo on ebay?

[Avanti]

http://cgi.ebay.com/3000-Helicopter-...QQcmdZViewItem

[dostacos]

did you find the motor combo on ebay?

http://cgi.ebay.com/3000-Helicopter-...QQcmdZViewItem

[Chop]

did you find the motor combo on ebay?

Yup, I ordered two sets (spares you know).

I’m still waiting for delivery. 8 to 14 days from China.

[j.m.]

You can also go to http://www.hobbycity.com/hobbycity/store/uh_index.asp
They have great deals on all things brushless.

Here is a good motor that would have a bit more power than what you are currently running: (and what's on the 'bay)
http://www.hobbycity.com/hobbycity/s...00W_Heli_Motor

Esc:
http://www.hobbycity.com/hobbycity/s...Simple_30A_ESC

Beware that some esc's used for airplanes and heli's may not be compatible with pistol style Tx's. Also, they aren't waterproof, and outrunner motors cannot be watercooled around the can. (it spins)

An outrunner (even the one on ebay) will have signifigantly more torque than the speed 400. You should be able to increase the prop diameter by a few milimeters and the pitch without worrying at all.

[Chop]

I received my parts today. I had ordered two 3000 kv motors but received one 3000 and one 5000 kv motor. Do I keep the 5000 kv moter or do I send it back?

What advantages/disadvantages does it offer?

[Dr. Jet]

If the 5000 rpm/V motor is the "Short Can" version, there is not much you can do with it in a boat. I have one and I finally built a little gearbox for it,; the resulting assembly gave similar performance to the 3000 rom/V motor in my micros. While it worked well, it wasn't really worth the extra effort and complexity of a gearbox.

[stablgr]

I was looking at these motors for a couple of Hydromites I'm about to start building. One is going to be for my 7yr old son and I was wondering if the 1700kv motor would power this hull. I'm not looking for blistering performance.

Any help would be greatfully received

[j.m.]

I don't know how well that would do. It might not even get the back of the hull out of the water.

You would definitely have to use a bigger prop to get it to perform well.

As for your son, a hydro might not be the best boat for a beginning driver.
(with a turn fin, he will only be able to turn one way at when he's going at any descent speed. Not ideal for a no-so-good driver.(as you make him seem))
A mono would be great, though.

As for you, check out the motor i linked to a couple of posts up. Should have a lot more power than the one most people are using, but it's not that much bigger.

[peells]

Ok I have seen these motors on ebay and do these speed controls that they come with work properly with a pistol grip radio? and one more question where do you get a coupling for a 2.26 mm shaft? I have found the 3mm shafts but no luck on the 2.26mm shafts (maybe I am not looking in the right places) and how do we know if the speed controllers are or are not compatable with P.G. Radios before we get them or is it just a crap shoot? just wondering since the pistix are no longer available and not being produced any more, that is a bumber those things work great so start making them again RC Hydros!!!!

[j.m.]

Don't know about the 2.26mm shaft...

Use this motor:
http://www.hobbycity.com/hobbycity/s...00W_Heli_Motor

It's got a 1/8" shaft.

Or this if you are looking for a top-of-the-line motor for a small hydro:
http://www.gobrushless.com/shop/inde...=SCHK2221-10V2
http://www.gobrushless.com/shop/inde...f=SCHK2221-8V2

Both of those motors are rated at or above 440 watts of power.

They will push these little hydro's along at INCREDIBLE speeds.
Those motors are kinda like the Neu's of inrunners.

Not the best, but they sure are good.

[stablgr]

Good question. Does anyone know where I could get a coupling for this motor?

[n.h.schmidt]

I make and sell custom motor couplers. 2.26mm works out to .089 dia. I can make couplers for that size. What size prop shaft? Typicaly for a simple one like this the cost would be $6 plus shipping of $1. With two couplers ordered ,no shipping charge.
n.h.schmidt

[Avanti]

Ok I have seen these motors on ebay and do these speed controls that they come with work properly with a pistol grip radio? and one more question where do you get a coupling for a 2.26 mm shaft? I have found the 3mm shafts but no luck on the 2.26mm shafts (maybe I am not looking in the right places) and how do we know if the speed controllers are or are not compatable with P.G. Radios before we get them or is it just a crap shoot? just wondering since the pistix are no longer available and not being produced any more, that is a bumber those things work great so start making them again RC Hydros!!!!

the mystery 30a work fine with my JR pistol model XS3

[peells]

N.H. Schmidt, That is great information to know,
John thank you! I have a 2.4 Ghz fasst Futaba and I have used Hex tronic's esc and they would start running with the trigger in the off position and go really fast in reverse and stop in full throttle so I bought a pistix and cured that prob. and thanks for all the information.

[stablgr]

I make and sell custom motor couplers. 2.26mm works out to .089 dia. I can make couplers for that size. What size prop shaft? Typicaly for a simple one like this the cost would be $6 plus shipping of $1. With two couplers ordered ,no shipping charge.
n.h.schmidt

Thanks, I'll certainly keep that in mind. I haven't sorted out what I'm going to use for the prop shaft. I can't work out the pros and cons between a piano wire type drive or one of the flex cable thingymajigs.

[Chop]

O.K., I worked on the boat tonight. I’ve been putting it off because I have too many irons in the fire.

I have the new 3000kv motor installed, put the stuffing tube back in, and have the electronics assembled. The ESC is slightly larger than the stock one, but there was enough room.

I’m waiting for the glue to dry. I will take pictures tomorrow, and might even get it wet at lunch time.

[Chop]

Well, the mini hydro runs good with the new parts (3000kv outrunner & 30a ESC). Tough getting the wires routed so that they don't touch the outrunner's can.

The prop got scuffed up somehow (Did my son run it up on some rocks?). On the straight-a-way it runs good, but in the turns it dies in cavitation. After a few moments the prop grabs and it takes off.

It looks like a very small, threaded propshaft (3mm?). I'm guessing that the prop should be played with.

No, it is not going to just be a SAW boat.

[Dr. Jet]

It's probably a Graupner threaded prop (4 mm threads). Try a K29 prop from OSE.

[Chop]

Damn, I just received an order today.

[peells]

Try putting a turn fin on the back of the sponson which is on the inside of your turns, I had the exact problem with my mono and I suspect the same thing is happining here, it was like adding power steering and I then could use full power in the turns. Good luck, (I vote your kid hit some rocks)

[Chop]

Sorry, I forgot to mention that I also installed a turn fin.

My bet is on the (slightly, chewed up) prop.

[peells]

I hate it when that happens!!! How about battery position? strut depth? strut angle? a jet engine LOL

[n.h.schmidt]

Hi
If you are using the original prop that came with the boat,it is a 26mm prop with a 2mm threaded hub. Offshore has new replacement props.I don't know if your prop shaft is also 2mm all the way or stepped down. Offshore used to have 2mm to 4mm adapters for the zig zag boats. That would allow the use of the other Graupner props starting with the K 29 and going up from there. I can make the adapter if Offshore doesen't carry them anymore. n.h.schmidt