BACKEMF

So here it goes, some pictures, bear with me as I might need to resize. Details of the inards shortly...


There we go...

BACKEMF

One more I think?

BACKEMF

O.k. this is a MHZ Micro fountain, slightly longer than the Gecko by about 2".

It boasts a MEGA 1615 3 Turn motor (400 size) , 6 IB1400's, Mamba ESC (cooling coming shortly), Ejector pin (wire) drive, Octura 427 ballanced & polished (Aluminum)prop. Futaba 3PM radio and micro F133 Rx.

You see in the bench and water test area a WATTMETER hooked up so I can see the free running amp rating and the approx. MAX amp draw by holding the boats prop underwater in the sink. Holding the boat steady while the prop is under load is a good way to test the amp draw at take off, which is usually when highest amp draw occurs.

When I bench tested the motor without the driveline hooked up it drew approx. 1.5 amps on a flat 6 cell 1400 pack, (been sitting a while). With driveline lubed and installed it was 2.3 amps(grease too thick).

When I tested it under load I could get it up to about 15 amps max. before the water was going nuts everywhere.

I believe if the pack was peaked up it would show slightly higher numbers but this is good since the ESC is rated at only 25Amps.

Real testing will be on the water. I don't expect blistering speed but who knows until I get out??

The main reason I can get away with a MAMBA controller is because of the Mega motors 6 pole rotor, basically it can do more work for less amps. If I wanted to keep up in speed and go to 7+ cells or lipo, then I would most likely need a bigger controller, but for now, light and low amps are aaaallll good to me. can't wait to test it, maybe Sunday??

Another way to gain speed and lower motor load is to use light Aluminum props and modify them by either reducing the diameter or removing the leading edge etc... But those are some other subjects.

My room is a mess whilst I build but hey you can see some of the other TOYS.

Cheers, more info later, maybe my buddy has a Vid Cam, I don't sorry.

BACKEMF

Heat sink on ESC with thermal electrical heatsink silicone.

BACKEMF

Out for a spin today at a man made 10,000 sq. ft. pond, (100 x 100). On 6 cells and the 427 prop it was a hoot and others there stopped to watch. After a while all the kids and adults were asking "How can I make min ethat fast?".

I think it was doing about 20mph not shure because of the limited space in the pond, I had to turn once I got to nearly top speed.

After approx. 6 minutes I had to limp it in. The drive dog came loose, darn. I didn't bring that Allen Wrench, so that was it. I did flip it a couple times but my buddy walked into the 18" deep water to flip it back. I am just charging the pack back up now to see what I was pulling.

So it is possible to run a MEGA 1615 3 turn on 6 cells on a MAMBA 25Amp controller. It looks like it may only draw 10'ish Amps with the 1400's and x427 Aluminum prop.

Can't wait to get to the bigger pond and make up the other 3 packs. The stick pack I used wasn't too great for the CG, so I will make saddle packs. I may try 7 cells but it was quite a handfull on 6 cells. It is sooo light.


After that 6 minutes of run time it all came back COLD[8D]. The only cooling is on the Mamba as seen above.

Megas cost more but they grunt out the work.

BACKEMF

I also made some guys upset with there NQD Hydros. Those things suck when stock, barely got on plane. Mine was mostly in the air with how choppy water gets in a closed square pond.

jdoug

zeeek1 - What is that you are using for a prop nut? Looks like a collar with maybe a set screw. I need something different than that heavy bullet nut on the Gecko.

Stokes

jdoug, why not thread a nut to a bolt (same diam as the shaft) and drop on a blob of 5 minute epoxy? then put the bolt into your driller and power it slowly against some light-grade sand paper....when it's all done just take out the bold and voila an end bit for your gecko. Make sure you lube the thread though - otherwise you won't get it out!

andrew

BACKEMF

The whole drive wire is one piece. It is a Die Ejector Pin. I got it from my friend Lou of LousfastRCboats .com (or something like that) We race together and he cam up with these one day. They are great but too much power(12 sub "C"'s) will snap them. they come as .125" all the way to the back stop, or like mine; .064" then it opens to .125" for the prop.

There is also one with .032" shaft and .125" stub. That thin one is for my micro shovel nose.

This is in the M. Fountain:

BACKEMF

It's a 5-40 thread on that stub. Hard, but not impossible to get bolts for it.

jdoug

I do have a nylock nut for it...but the nut has a bigger OD than the prop hub.[&o]

Al P

Those pins are from D.M.E. ( http://www.dme.net/wwwdme/ejection.asp ).

I use them in the tool & die industry also.

Drawback - very expensive.

BACKEMF

Lou only charged me $5 each, not bad for a driveline.

It's o.k. if the OD is bigger than the prop hub. It will not effect performance at all. If it were in front, then it would lower performance. Locknut is fine, I use them too.

Just put a tiny piece of Silicone Fuel tubing in between the prop and nut.

If you can find tubing tight enough, you don't need a nut at all.

jdoug

I've never done that (tubing) and am worried that I will lose the prop. I'll try the nylock first and see if it hinders performance any.

Did you get the aluminum prop directly from Octura? ...or where?

BACKEMF

I usually get my props from Fine Design, or Offshore Electrics, but once in a while I order direct to Octura. It's easier to order from the first two people because there is no minimum order (the last time I talked to Octura that is).

The Aluminum ones are nice and easy to sharpen, and balancing I only do for over 27000 RPM'ish; under that a small aluminum prop (32mm & under) needs no real balancing.

The better the prop is finished the lighter the load on the electronics usually, and better speed.

BACKEMF

You would have to really hit something hard with a prop to knock it off from just using tubing, and an aluminum one will usually be toasted after that hard of a hit.

Beryllium Copper is tougher but the prop is always pushing itself on when spinning.

jdoug

OK...I'll give it a shot. I'll have to get the prop first and get it worked. I was thinking that maybe just the force of the water when going from full throttle to coasting would possibly pull it off.