mineralvann

ive gotta say i envy you on that programming card, i have to guess my way through the programming as the blinking doesent always happen like the manual say, and i hate the guy that thought that holding in a button while connecting the battery was a good idea for programming an esc, deans+one hand should be a olympic event

TwinJetMax

Haha so true. I got really good at that. The trick is to pull the trigger and hold the esc leads with one hand and use the other for the battery.

I got all of my nitro gear today, and picked up a motorbike starter motor for free. There is no way that I am going to spend NZ$300 on a starter.

sundogz

You, probably Our customs department in Jamaica,NYlikes to check things out before forwarding them on. That usually takes another week or so. Our tax dollars at work!

grael

I've struck the first difficulty of significance in my mini jet project:

I can't get more than 4 amps out of my r2hobbies "20 amp" Tuborix speed controller before it cuts out. I have a clip on DC ammeter, and the low ESR capacitor on the ESC should average the current enough for me to get a reasonable close reading. This is a puzzle though, because the 20 amp ESC is the one R2Hobbies recommend for this motor. to get 4 amps, I had to cut down the 35mm impeller until it measured 14mm diameter, and as the hub is a minimal 6mm diameter, that's actually only leaving a radius of 3 to 7mm to actually pass water[:-]

I'm at a loss to know how r2hobbies calculate their product ratings, my assumption would be that the ESC ought to be good up to 20 amps, on either 2 cells, or 3 cells, and it barely gets warm, on the 2 cell LiPo running the speed as high as I can get it before cutting out. Any bigger than about 14 mm on the prop, and the ESC cuts out before full throttle.

The motor's hardly warm, has anyone else had experience with the tuborix products?

aquajet

Grael have you checked the unit is not sensing low voltage under load and cutting out

marshr32

I havnt had any experience with the controller you have grael, but its not the low voltage cut out doing something funky is it?

Sundogz, those props would be perfect, and they are a pretty good price too. I wonder how they are made (soldered, brazed, cast)

grael

Aquajet,
yes, that was one of my thoughts. Doesn't matter whether it's just charged, still the same fault. Either the current feedback resistors (load sensing), or the battery voltage detection circuitry is no good. [] I've had current meter and volt meter hooked up on the battery end, and no issues with either of those.

Eventually, I tried it out on a 12 volt lead acid battery, figuring that it's stored voltage would be no more than that of a freshly charged 3cell LiPo. No more go.... and it's supposed to be a 2 or 3 cell ESC.

I've done an autopsy on it, and both the RX and Microcontroller output voltages are good, the original soldering is poor though, I imagine they would have a very high defect rate with many never leaving the factory.

I've been checking out hobbyking too, they have a HUGE range !
I'll probably get a couple more ESC from there and see how they go, also a couple of 1amp hour 11.1 volt 25C LiPos.

Has anybody had good experiences with small ESCs driving motors around my specs ? (2500rpm/V, supposed to be max 12 amps.)

headhunter23

Try resoldiering the leads, otherwise it's probably a bad esc. I've had a 1 20 amp and 2 25amp esc's from them and have worked fine. But I've also had an issue like yours too... either bad esc or bad leads.

aquajet

If you lucky you may come right with resoldering. maybe check the curren sense resitor doesnt have a dry jpint . you would need another similar one to see if the value is correct
Be very careful about putting a 3 lipo esc (12.6v full) on a lead acid (13.8 full) Idid it with a 6 lipo esc on two 12v lead acid batteries and it litterary exploded. lucily under the cover of the boat . Blew the input , output and servo wires off and then finally the flames went out due to no oxygen , but relit when Iopened the boat. . motor was still ice cold and it was running 40 amp on a 70 amp esc, so Ican only think it was too much voltage, by about 4 or 5 volts. new esc lasted under 5 min. I was measuring current with a telemetry system , but never worried about the voltage as i was in too much of a hurry.

bayshun

Man i wish hobby king would hurry up on delivering my esc batts and charger its been 2 weeks and i ordered express shipping. i know the esc was out of stock put come on 2 weeks lol


Ben

marshr32

My last order took nearly 2 weeks just to get out of the warehouse and they had everything I ordered in stock! I think they are just really busy all of a sudden for some reason.

Grael is it one that you have to program the cutoff voltage into or an auto one?

grael

marshr32, aquajet, headhunter23,
thanks for the ideas.

This ESC only runs 2S and 3S. (and in this case, poorly)
When I couldn't get it to run on 2S properly, I tried a 12 v lead acid cell, but that had been sitting unused for at least a month, so I'm guessing it wouldn't have been above 12.5 volts. I've taken a picture of the power side, you can see the soldering is pretty hopless in places, but what I found more interesting, is that instead of one type each of N-channel and P-channel MOSFETS, there seems to be an assortment. Basically, these function as a very fancy 3 phase inverter, and so anything more than two types of MOSFETS in this area indicates a problem in the manufacturer's stock levels, a later repair with different MOSFETS, or incorrect parts placement in the first place.

I think in retrospect that even if I'd had a 3S LiPo, it would have stopped this ESC from working, the startup seemed to be erratic at times, and as mentioned, it wouldn't deliver more than 4 amps at best.

Edit:
I've sent r2hobbies a long email describing the "quality" of the circuitboard and so I'll see how they respond. [X(]

Quicksilver

^^^^need some esc with your solder? wow lovely! definitely got a few different mosfets in there with the ounce of solder. I'd be rather upset with that [:@]

marshr32

Yeah its a bit of a gamble with these cheap escs. You'd think they would spend just a little more time on getting them right, but there cant be the $$ in doing that.

From what ive read they work as an H bridge so there should be a high side pair and a low side pair for each output wire? Are the P and N channel FETs in any sort of pattern or just placed randomly? Cause that would definitely stop it working properly!

Edit: I see what you mean by different types now, like different manufacturers or whatever. That top let FETs soldering is awesome, whats wrong with that? [sm=lol.gif]

grael

Quicksilver:
Maybe all the solder from the top side dripped down the vias to the bottom side ?[8D] Well, maybe if they cooked the board hot enough for the solder to properly melt...

Marshr32: I think all the mosfets on one side are Fairchild, though not all the same date code. I presume they are all one type:
http://www.datasheetcatalog.org/data...d/FDS6680A.pdf (N-channel, 12.5 amp, 30 volt. If you take into account voltage overshoot, and two high mosfets, two low mosfets per channel, then this is a reasonable sizing for a 20 amp ESC.
On the other side, all have 4407, which I've traced to a 50 volt p-channel Mosfet spec:
http://www.datasheetcatalog.org/data...rf/irf3205.pdf
However, the other numbers on the chip will be batch or date codes, and none of them are the same... I told my supplier that I think they've been sourced from a spare parts bin.

Also of concern, is I found two unpopulated SMD footprints, one connects to pin 31 of the ATMEGA8 chip, which has the alternate function of TX. Since my programming card won't program the ESC anymore, but does light up, I'm thinking that it may be a component that "fell off", and might be part of the programming card communications circuit.[:-]

blizzzarddemon

have an abc hobbes jet ski im looking at makng it faster maybe brushles anyone have any ideas

sundogz

Have you bought batteries yet? An easy mod is to replace the 2 speed for a brushed esc. A good 30Aor a cheapie 50A will do fine. And then run it on 3s (11.1v) Lipos. The stock motor is good for that, and quite peppy!. Depending on the motor (someseem faster than others) you may have to mod the intake (search this thread) to stop cavitation if it's too fast. This is a good RTR boat, it is built well. Sdg

Running Beer

Hi, I'm putting together a single 28 mm Kehrer jetsprint boat with an 800 motor on 5s. Anyone out there done this, have any tips etc?

blizzzarddemon

im runnin a traxxas xl5 esc i dont have any 3 cell lipo except for the one that comes with an eflite blade 400 and thats the only charger i have for lipo is what came with it as well

sundogz

That's a good esc, but can only handle 9.6v (8c NIMH), which is still repectable in this boat. When you say 'running', what batteries are you using?


Areseaer: You may have saved me from some grief. Check this out www.rcuniverse.com/forum/m_8985728/tm.htmThey have pulled all but the 35A and the 180A Turnigy esc's (Seaking) from HobbyKings catalog. Seems there is a Version2 update that will supercede. Thx!, Sgd.

areseaer

Yeah I've been watching that. The one I ordered said version 2 so I hope I'll be ok with that being the good one. The guy getting the [link=http://forums.offshoreelectrics.com/showthread.php?t=9508]180a[/link] esc I told you about before said his are delayed because they have been recalled to.

sundogz

Mine didn't say version 2, but maybe I'll get a good one. I've readgreat reviewsabout the "version one" 180's, so it must be an infrequent occurrance. We'll see. Sdg

grael

I see everyone is far too busy assembling boats and running them to chat on here !

I'm ordering a range of small motors:
rescue boat, I'll try to drive about a 50mm water prop/jet or 9 inch diameter 3 blade air prop with this:
1) 700kV outrunner.
I was thinking of a twin hull for this, with a bridge mounted fan, and a glass fibre rod catcher mounted underneath. I can make it to take lead acid batteries or LiPo, but be based around having huge thrust, and only just enough speed to plane. Hopefully, once on the plane, the motor current will go right down, and give me long run times, so long as I keep the weight minimal.

mini jetboat testing motors:
2) 3200kV heli outrunner
3) 4200kv inrunner
4) 6200kv inrunner
(I already have a 2500kv outrunner)
2,3 and 4 are all slightly heavier, more powerful motors.
(remember that my boat is so small, I'll be using a really small diameter jet unit, so a super high RPM still doesn't necessarily correspond to cavitation, as the tip speed won't be as high as that of a bigger diameter impeller running at the same RPM)
4 x 1A/Hr 11.1V LiPos
3 x 40 amp heli brushless ESCs,

I should see the gear mid next week. The motors I've ordered should all pull more amps than the 2500kV outrunner I have and the heli ESCs are at the best amps/price rate I could find, and give me plenty of headroom for more power in my tiny boat. I went through all the product reviews on the website I ordered from, and couldn't find anything negative on these particular ones... so I'm hopeful. The bigger weight combinations should give my boat a huge power to weight ratio, so I'd better seal the hull up well !

I've made 2 hulls, neither is to a good standard of finish, but they are good enough that I will get a good idea of how well this design of hull will perform in the water...
One is in epoxy/glass/carbon strand/glass, the other is in polyurethane/Dynel/Glass. I bonded the decks after lightly sanding with polyurethane resin, seems to be pretty strong. If the hulls perform, then I'm considering a full shell mould for the inside and outside of the hull and resin infusion vacuume moulding. It's the only way I know to get a really good finish and perfect resin penetration with no voids. This boat is small toy sized, but I want it to perform better than the full sized jet sprints, and be worth using as a basis for club races.

sundogz

Grael, that is surely a futuristic design, I hope it works as planned. I do have some reservation about the step in the nose. I realise you want it to come up to plane faster/easier, but introducing air front and center might cause lower thrust from pumping bubbles - and I have had dim results with the frothy stuff myself.

These boats on the smaller circuit should not need to be as fast (top end), but will need to focus on torque and control. The top speed on a smaller course will not approach what we can do on open water, but you want the boat to 'holeshot' like a jackrabbit when required. I predict control will be of upmost importance, as the tight turns will demand quick, positive reaction. This is exciting. I can't seem to locate a hull design I am happy with in the smaller scale (except that first one ISIRC10 showed us! hint,hint) and am anxiously monitoring your progress. Best wishes!

On a different note - vector steering. Vector-steering boats steer by shutting down one motor/prop (I usually don't like that approach) but what about 2 small jets with no steering nozzles mounted on a sprint hull (short, wide) controlled by vector steering? Would be interesting to try.

Tear Into Jet Sprint Motor swap update:

Finally got to run the knockoff with the new 3200KV heli outrunner and it was a whole different experience! And as predicted by Marshr and Danfurst - after going thru the 'tail wobble' (formerly referred to incorrectly as chinewalk) stage it's smooth sailing (if you can call w.o.t. madness smooth!) Whole 'nuther realm, the outrunner. After a 5 minute run I checked temps and the motor was getting hot to the touch so may need to use a water cooled mount. I had one laying around, but the motor bolted right up to the jet, and used the same coupling, so I thought I'd try without first. Battery (2800ma 30C 3s) was cool, as was the 35A Seaking esc. Here is a video:www.youtube.com/my_videos_edit I highly recommend 3200KV/11.1V or variations in this boat. This is an exciting enough speed with this hull and should give more play time than the faster motors.Yeeehaw!

BBY OM21 Motor swap update:

The new KD36-50-11S from HobbyKing brought the Rapid Runner to life. I had forgotten the canopy, so had to cautiously run it topless. At top speeds it developed a completely new wobble - as if I was turning it starboard to port rapidly, it dipped side to side:www.youtube.com/my_videos_edit I tried bending the ride plate up some and it reverted back to the hopping out of the water thing (bent it too much) and after several tweaks was still not satisfied. Am now going to remove the ride plate extension (leaving the shorter one) to see if it helps. I think it is flexing too much for these speeds. This hull with the Nacelles type jet mounting has sure been an experience (?[> and am hoping it will settle down with some more tweaking. It may be that Nacelles mounting just doesn't scale down well and is unsuited for lighter weight craft. But I haven't given up on it yet! Stay tuned...

ISIRC10

"I can't seem to locate a hull design I am happy with in the smaller scale (except that first one ISIRC10 showed us! hint,hint)"

well, you know what? that hull is of little use to me and it is just laying around on the shelf. I would be glad to see it running. If you feel that you can overcome some of the mistakes I made on it (the delta/deadrise) I am willing to ship it to you for free (as long as you can pick up the shipping costs) I am 16 right now so mass producing hulls isn't what I have in mind, but I can always get rid of one! However, pending on how testing with my new and improved hull goes, I may have to make a few more of these... I think that you will like this hull, Sundogz - I am quite fornd of its design and hope it runs as well as it looks.

Now for the specs of hull #2...

length: 35cm w/o jet
width: 15cm
height of transom: 4.8cm
height of hull w/ hatch: 6.3cm
weight: 82.6g

IMHO, I think that this hull is MUCH better than the previous one. I may be making copies of it in the future...