Cheap Mean Machine Help

[befu]

Bought a mean machine off of the swap shop here. $110 del for the hull, drivetrain and servo. needed a motor, speed control, prop, RC and batteries.

this thing takes a lot to get up on plane! Ok, it weighs in at 5.5 pounds RTR. the drive train is nice and free, gap for flex shrinkage. Bottom of the strut is even with the bottom of the sponsons and level. I tried a 38mm prop, no go. Then 40, 45 and then a 47! The 47mm plastic prop works and gets it up on plane. I was running 2s, 3s and 4s. COG is like 9.5" forward which is 32% of hull I believe. Prop is about 1.75" behind transom.

What size props are others running?

Oh, I decided to see how cheap I could build this thing! I went with a Turnigy outrunner for $19! A turnigy 3648-1450kv motor, we will see.

I also bought a hobby king SS 90/100 speed control, water cooled and proofed it. Added a BEC chip to the heat sink, works great for $30 so far. Added a prop and for $160 I am RTR. Used my Turnigy 20C batteries for right now.

Made my water cooled motor mount. So far, everything is very cool!

pics attached, video coming

Brian

[Chilli]

Try bumping up the strut height at least a 3/16 inch. I think mine is set at 1/4" bottom of strut to bottom of sponson with a degree positive on the strut (prop end tilted up).

I use a M545 to get 45 mph, but thats with 4s2p and a beefier 10xl motor turning 1734 rpm/v.

Have fun with it!

[befu]

Test video

This was on 3s-1800 x2 for 3600 Mahr. it ran for a solid 5 minutes so 12c at WOT. 12 x 3.6 = 43 amps.

Now, it wasn't bad, but definately not a speed demon. The other day i ran it and it was really windy. had 2-4" rollers out there. The boat was completely leaving the water even at that speed, looked very "offshore" realistic.

So, after this run on 3s, I decide to try 4s. I have 2s-2200's. So I put two each in parrallel and then put those in series. OH, I also lost the 47mm prop, so I went to a 47mm 3 blade. man, was it slow! Lost about a third of its speed. But I decided to time the run to see how long the batteries lasted. After about 8-9 mintues, I gave up and brought it in.

Well, putting it away and noticed I never put the series connector in. I was running it on 2s-8800!

so I put the series connector on, with just two of batteries for 4s-2200 20/30c turnigies. It ran MUCH better then. Video was full by then, so will have to get back out and try it again.

[ozzie-crawl]

i run a 8xl in mine, props i run are m440/3 pranther 215 for about 3 min run time at around 45 mph
for shorter runs a m545 gets me in the 50s

[Jeff Wohlt]

I run a 9Xl and 4S and I think a 642 prop and she runs out good. I had the same issue out of the hole. I did not raise my strut I think I dropped it in the water deeper. She jumps now.

Just adding more prop is not the key. Just more slippage when the prop is up higher. I want half the prop in the water while on plane. Raising stuts lower amps but you are also are getting less prop in the water. Stick with one prop for some testing. 642 and m545 is pretty good. M545 is pretty big looking but I like it.

[bustitup]

your on the right track

this is x640 with 2200 kv motor 46mph 2x 2s 5000mah 30c

click here for video

[Chilli]

Reddywatts goes up higher with the strut and Jeff goes lower. Not saying either is right or wrong. Play with it and see what works for you. Let us know what happens,

http://forums.offshoreelectrics.com/...hlight=machine

[Jeff Wohlt]

Deeper also gives a cat more hull lift...depending on the props. What I am saying is deal with a decent size prop but the more you put in the water the higher the amps but more lift in general...and speed.

On hydros you raise the strut to give a nose up lighter ride.

[befu]

amps

Of course, now I am getting into the high amp range again, which I wanted to avoid due to exploding speed controls and expensive batteries. To get this thing running well, will probably need to go to the 6 cells and drop the prop down and smaller. Still going to be a current hog! Heck, it was running 44 amps on 3s. maybe I will try that again and raise the prop to see what run time does. If it doesn't drop much, will probably end up selling it and going with a smaller mystic.

Two 3s- 5000 - 20c will cost $56 a pair for 6s from HK, + shipping. Batteries will cost more than the boat with 3 sets!

[befu]

4 cells

Ran it again tonight on 4s - 4400 - 20c.

Ran well, video attached. Pond was like glass and the boat seemed glued to the water and slower. Still ran well.

Ran for just over 3 minutes when the boat died. One of the speed control leads came desoldered from the bullet connector to the motor. I have never ran anything with this much amperage, melted the solder! i guess I need better solder to run this setup.

I measured the batteries when I got them back in, still at 15.18 volts for 4s, or 3.795volts per cell. No idea on the amperage I was pulling since the boat shut off before the batteries started to drop. If they were dead, it would have been about 79 amps. so i know it is well below that.

Setup changes: I raised the strut 1/8" above the ride surface and gave it a 2-3 degree upthrust to lift the bow. With the smooth water, maybe my COG was to far forward.

Motor sounds like it is not laboring at all to push that prop. It gets right up to its max RPM, doesn't take long at all to wind out. I think it has plenty more in it, not sure I am the one to do it. need better batteries or a data logger. Motor and speed control are rated for 6 cells. Speed control 90 amps, motor 70 amps for 20s or 1600 watts max.

You tube clip of some of the shots. i was holding the camera and radio at the same time, so cut me some slack on it, ok

Brian

[befu]

cooling

In another thread someone had asked me how I cooled the outrunner. Here is a better picture of it.

Aluminum mount, has a single water pass through it. haven't pushed it real hard yet so I am not sure how well it works, but it isn't getting hot.

[Jeff Wohlt]

I think ot get the MM really going you need 6S and a M545 prop...maybe a bit smaller but a KV of 1500-1600

[Xfactor]

For the money you spent she runs nice though.

[befu]

testing

Yep, going to do some testing.

I am going to run it on 4s and 5s to see what it will do. i have a data logger now so I can get amperage reading.

Also have a better prop selection. The 47mm 3 blade pops it right out of the hole, but I wonder if it is hogging current. That is a lot of prop on the back of it. Will go with 2 blade props, 43 to 47mm is the range I think I will try.

Will also video it so see if we han estimate speed as I do not have the gps unit yet.

Still, for $160 RTR w/o batteries, it is not a bad sport boat!

Brian

[blackcat26]

I'm with Jeff on the voltage, you need 6s to get power from this low of a Kv motor. Higher power batts would not hurt either (better too much than not enough) You might also be asking alot from this motor since the length is only 48mm. (most are running 75mm can in this size hull)