telleslattari

thank's a lot rebuilder and nick 30!
i'm going fine in the construction of my cat,
you guys have been decisive to it.
with out your's adivices, probably i woud buy stuffs that woud burn out really fast
and nothing would work.
i'll put two of 3 s
can you help me to find a good charger / balancer/ discharger?
and how to use it... rs
im thinking in this one, what do you think?
http://www.hobbycity.com/hobbycity/s...idproduct=6590
GT A-6 Charger/balancer/discharger


Spec.
Input Voltage: 11~18v
Circuit power: Max Charge: 50W / Max Discharge: 5W
Charge Current Range: .1~5.0A
Discharge current range: .1~1.0A
Ni-MH/NiCd cells: 1~15
Li-ion/Poly cells: 1~6
Pb battery voltage: 2~20v
Weight: 580g
Dimensions: 133x87x33mm

is there any other that you recomend?


that ESC it's the one that i'll buy, 

 http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=8946&Product_Name=Turnig y_Marine_120A_Brushless_Boat_ESC



with a ubec TURNIGY 5-7.5A (8~42v) HV UBEC for Lipoly
Spec.
Output (Constant): 5v/5A or 6v/5A
Input: 8v-42v (3-10cell lipo) High Voltage
Size: 48x27x9mm
Weight: 37g
Quiescent current: 20mA
Type: Switching, however because of the noise reduction (thin metal case & filter) this unit gives the same noise as a Linear BEC.
http://www.hobbycity.com/hobbycity/s...BEC_for_Lipoly

but, how can i conect two batterys in a one motor?
do i have to buy a cable to do it, dont i?

and i cant find a cable maybe the name is ~drive dog~ i dont know,
to conect the motor into the prop, this hardware part i dont know were to buy, an what to buy...
i`ll put this week a picture of my cat for you maybe help me.

but thank`s, really thanks~
leo

telleslattari

sorry by the double post.
which motor do you recomend:

KB45-12L 1400kv Brushless Inrunner
Kv: 1400RPM/V
Weight: 449g
Shaft: 6mm
Size: 63x45mm
Voltage: 36v
Highest rated power: 2246W
This size motor will fit our larger 5inch and 4.75inch EDF perfectly. (same mounting holes & shaft size)

or this one:

KD36-74-09XL 1900kv Brushless Inrunner

Front mount holes are 25mm apart.
Dimensions: 36×74mm
Shaft size: 5mm
Weight: 370g

Spec.
Kv: 1900rpm/V
Idle Current: 2.6A
Resistance: .0091
Max Amp: 75A



and do you know were to buy a colling system to they?

rebuilder

Here are my thoughts..................the KB 45-12L is gonna work fine................but its heavier and has a 6mm shaft, keep those thoughts in mind. The KB36-74 1900kv is just a bit on the high side for kv in my opinion, which is why i posted earlier to everyone on this thread that it was kind of on the edge................i wish it was a 1600-1700. This whole idea of the KD motors to start with was due to their inexpensive price....................i personally use Feigao's now and they are of better quality, they cost twice as much too. On my 6s boats I use between 1400-1800kv motors depending on the boat size etc.........If it was my boat telleslattari, i would buy this motor if i were going with a 36x74: http://www.offshoreelectrics.com/pro...prod=fei-540XL , in either the 10XL or 11XL.

Im not saying that the 1900kv wont work..............it just needs to be properly water cooled, with a jacket, and err on the side of underpropping it.

Here is a Y harness to connec t two batteries in series: http://www.offshoreelectrics.com/pro...harness&cat=75

Here is a cooling jacket for a 36mm motor: http://www.offshoreelectrics.com/pro...ose-mjacket-XL

At least we're on the other end of nick's 4200kv motor attempt that went like 3 mph...................

wetsleeves

Im going to go for twin 540 Feigao's in my cat instead of the KB-45s. Now the question, which Feigao's 10XL or 11XL and ESC.
Batteries will be 6s 25c or 30c 5000mAh and prop around 45mm. Im going to buy Turnigy Lipos and see what there like.
My charger is a Thunder power 1010c plus Thunder power ballancers. Is there a certain type of lead that I need to get so I can connect a batterie to the ballancer?
Thanks for all the advice to everyone in this thread.
When I said I wanted to do this boat on a budget it was because I all ready have a high end build with my Electric Mystic cat and my large Mystic is going to get twin turbines so I just wanted this build to be within reason.

Peter

wetsleeves

I Was even thinking Feigao 12 XL which would have the rpm a little over 32000.

rebuilder

This is too funny..........................cuz here is a pic of one of my 6s boats.................the Feigao 12XL, with the turnigy 120 amp esc which i recommended, and its on 6s......................I guess im preaching what i practice....................thats backwards isnt it?

rebuilder

BTW...................since Feigaos have been put on the table, here is a Very handy Feigao chart i use quite often. It has the KV and Max amp draw of each motor listed by size. S = 50mm, L = 60mm, XL = 74mm lengths. Now you can figure wattage based on the amps and your voltage.

wetsleeves

ok cool, twin 12XL Feigao's with turnigy 120 amp esc on 6s. that just may be my set up on this boat.
What size props do you think I would need and what speeds do you think she should reach?
Thanks once again

rebuilder

Wet.............to be quite honest, i've done two dual brushless setups........one failed, one was kinda iffy..........dismantled them both. I have trouble getting the motors to spin "together" and spool up at the same time. I was using a "Y" harness from the esc's to the receiver and it just wasnt going well. One motor would be spinning already at 1/4 throttle and the other doing nothing....etc. Thats why folks dont use them in cars either. It has and can be done in boats...........maybe there is a "sync" type program or device to get them to run smoothly together. Dont you have a big mystic on Duals? How is it workin out?

Now, as far as the motors and KV and such i think the 12XL or 11XL would work fine, both on 6s, 42mm props max.............that should be fun!!

wetsleeves

I have a 44inch mystic that has twins neus in it, running gear came out of my red hydrolift cat. The reason I put the motor set up in the mystic is that one of my neu motors tore an engine mount out with part of the hull.The hull gave way. I ended up getting a new Hydrolift hull with carbon fibre inlay which is why I wanted to get a new set up without breaking the bank.
My motors seem to rev up together without a problem (when it was in my old hull) but I havnt ran them yet in the mystic as Im waiting for thunder power to send me my batteries..
The large mystic that ive got will be twin turbine (was going to go electric but I think turbines would be nicer)

nick 30

same reason as all the other guys for having a single motor, to many problems

you can get 1 decent motor for the price of 2 or less and have only the 1 motor etc to worry about then

put in 2 x 3s batterys, 4000mah on either side to balance the boat, plus with 2 x 4000mah in series will give you more power than a single 6s battery would

wetsleeves

A single motor is more effiicient and a lot easier on the bank account than buying twins and alot easier to set up, but I like the scale look.
If I wanted to go for speed records then I would probable look at building a cat with a single motor. I just want a set up that would be fun.
Ive also got the drives already installed so its a little late.

nick 30

so double drive it is then, however, next time you build something at least you'll know design everything first then build second

i must say that does look pretty sweet

i would go with the feigao series motors then, 580 long series and propbably one's with the lowest kv rating
 2x 150a ESC (with BEC)
 a reciever with BEC
 parallel harness to connect the ESC's together
 series harness to connect the batterys together
 y-harness to connect the leads together to the reciever 

MalcolmX

i didn't reralise that twin drive was such a pain, after all; nearly all the German Cats are twin drives.
single drive is much cheaper anyway.

nick 30

far less trouble to sort, half the components to go wrong plus alot of racing and things are with single drive's

MalcolmX

YES, because you need two ESCs, two sets of batteries, two props/drives etc.

ok, so you have to get a single very powerful engine, but it'll still be cheaper in the long term.

nick 30

thinking about it, what if he makes the shafts belt driven, put a pulley or equivalent on the motor shaft then have belts to the shafts like they do on some rc heli's for the tail rotors

rebuilder

I have pondered that too. It obviously can be done, a big 580 size brushless running both shafts with one geared in reverse rotation for exact counter rotation.......... zero torqu roll!

MalcolmX

you'd loose performance, too much friction between the belts and gears etc. ...too many rotating parts

nick 30

how about gears, large one on the motor shaft and 2 smaller ones on the shafts

MalcolmX

yes interesting, gearing up!

better with a belt, because with gears you only have a few teeth in contact, so you'd need to to design it very carefully, to reduce movement, because at 30 000 rpm; those gear teeth might get ripped off, but a belt has far greater contact

nick 30

malcolmx

your agreeing with me now but you said it would lose performance and to much friction, with belts, your gripping half the gear on one side,make all cogs meat so no gear stripping, use belts and gears from rc heli's, i might even do a bench test on it and see what happens, i got most of the parts

my eldest boys boat has plastic gears, motor shaft and prop shafts, not much difference in the size of gears, trouble is working out the correct gear ratio, having a look at gear boxes, a choice of 2:1, 2.5:1 or 3:1 ????

MalcolmX

you'll definitely loose performance, because there will always be friction between the rotating components, plus the bearings etc, but not too much.

gear ratio maybe 1.5 to 1 or 2 to 1, take a look at the MFA 850 TORPEDO gearbox, but you'll have to swap the gears over

ryan_t888

One motor with two outdrives is going to re-introduce all of the problems. A high powered setup with a belt drive is not the most ideal situation. When loaded, belts are tensioned on only one side. The other side is open to vibrations and belt slap which could cause havoc on a high powered setup with large load and high RPMs. You will also need a larger belt than what is typically found in a (RC) Heli or Car.

Above all, I would recommend either one motor running one outdrive or two motors running two outdrives. If you wish to split the power of one motor to two outdrives I would recommend going with gearing and do not overdrive the system. Gear reduction is key.

Ryan

MalcolmX

sorry my fault, what you're doing wont work

1 rev of the engine = 2 revs of the prop ( but for twin screw this will be 4 revs) this is far too much loading on the engine, this will cause the motor to overheat quickly and to run slow, let alone the huge Amperage draw, you'll probably blow the ESC as well......it needs to be direct drive or geared down only, do not gear up.