CROSS REFERENCING??

Got a copy of Hugh Bright's manual and it answers a lot of questions. But not figuring out the equation 12v 895 motor=x specification ESC. 895 specs lists 368w-wattage?? I did stall and got 400ua but don't know how that applies. A lot of ESC specs give kv numbers which I don't understand. It seems that the latest ESCs dole out lower voltages for RXs and servos but have no clue. I've done a few car radios and upgraded the regulators of all my motorcycles but this is a bit tougher. Thanx,GJ

GJ

I'm not familiar with the 895 motor - I'll try and look it up - but one thing you have to understand. There are two types of motors currently in use in models - brushed and brushless.
The former are the traditional types and in the UK at least have numbers like 385, 545, 800, 900 etc. These use ESC's which will drive one or more motors from one ESC, depending on maximum current draw of those motors. They use two wires - positive and negative and will operate direct from a battery if required.
To size an ESC for these motors you need to know the maximum current draw of the motor. BEWARE of Chinese ESCs. Their maximum current claims can be exaggerated
Brushless motors use three wires and each motor must have its own ESC. They are measured in Kvs which means thousands of revs per volt. They will not operate direct from a battery. These were designed for model aircraft and in consequence many of the ESCs are forward only. If you go this route then ensure you get a forward/reverse esc. The other measure of a brushless motor is it physical size given as diameter and length eg 2836 is 28 mm diameter and 36 mm long.

In both cases you can buy ESCs that have a Battery Eliminator Circuit (BEC) that will give you 5 volts for the receiver regardless of your drive battery voltage.

This is only a brief outline, and about the limit of my knowledge   , but may give you something to research. Hugh Bright's book was written before brushless motors became common.

Barrie

Got another reply from RCU that helped a bit. He said 400ua seemed too little as 12v 368w was 30a+ indicating a 1/2 hp motor. This unit is used in cordless drills etc. As far as motor sizes it seems that is fluid such as a 380 being a 400 . perhaps the 895 is a 900 family 775/795=800?  I'll be retesting motor stall and prop in water when my coupler arrives. The esc I'm looking at appears intended for big 4 wheeler trucks with fan cooling 7.2-42v 320a input and specs for forward/reverse/braking loads. The specs also refer to nihm or lipo cell numbers to power it meaning I suppose in a car it wouldn't be run off motor batt. It seems the aircraft and surface vehicles have gotten most of the development in recent decades. Every reply clears a bit more fog. Thanx, GJ  We're having 60F heatwave

Milliamp vs microamp. When retesting I notice meter has both ranges. With clothespin test got about 1000 Ua. more than twice finger squeeze. I may have posted 400Ma instead of Ua somewhere. Par for the course-yesterday I was sleepy by midafternoon forgot my meds at breakfast. I'll blame 60 degree heatwave.

I have a question before I jump in with a ton of facts on watts and calculations for motors....


Are you wanting to use a brushless setup or a brushed one? Because the maths are very different animals for either one...  brushless also requires a lot more base knowledge and it far less forgiving for messing up over a dc motor.

RR
He has a brushed motor - an 895 he says. There is another thread about his model https://www.thercmodelboatforum.com/t2136-nearly-75-newbie

Barrie

I was trained to be a teacher long ago. Called son-auto mechanic training in computer science now. He says check meter fuse-both meters blown. Also meter w bad fuse still gives funny readings. Looked at Hugh's book again and ahha use only high amp range. So 1.03a free, 1.3a prop & shaft, 2.6a in water, 10.3a stalled. So real numbers seem to indicate the escs rated @ 20a should work and perhaps no need for a fan cooled one. Like forgetting meds the other day or trying to recall info learned decades ago. Now my feet are in the mud so I can wade.

OK, with the readings just posted does the one I've been looking at seem right? Specs are input 7.2-16v, 320A, , fan cooled, bec 5.6v/2A,continuous output-320A forward, 160A reverse, 540A brake(obviously car related).

Totally overspecced - even if these are Chinese amps. What you need is at least a 20 amp forward and reverse esc without brake. The brake function means to go from ahead to astern you have to go to neutral twice before going astern - not good if you're about to crash into the bank.

Something like this from Hobbyking in Hong Kong is a good fit.

https://hobbyking.com/en_us/hobbywing-quicrun-60a-2s-3s-waterproof-brushed-esc-for-1-10.html?

You may be able to find a local US supplier of the Quickrun range of BRUSHED waterproof ESCs.

Barrie

lol yes i agree 160amp i would expect on a forklift or a brushless setup for hydro racing not a normal cruiser...

truth be told ... 

Ignore WATTAGE on model setup... its only going to make things extra confusing and unless your running a brushless setup then its just a bit of math to know but wont actully make the model go...


so anyway i looked at the other thead with the motor you have...

you said 895.. so thats is one of the top end of that can motors ranges.. thats ok ( they start at 540. 550. 600 , 775, 795 and 895. ...

I'll make it really easy for you.. those motors cant run more than 12v ... they burn out to fast. 7.2 V they love.... 6v ok ... but not the best for them getting the RPM up...

 i would run that Motor on 12v easy Anyday and never worry... they draw around 25 amps on first hitting the thottle and run constant at 12 amp draw rate...
 
Notice:
The current more than 10A when it starts. It is recommended to use power supplies such as switch power or battery''

Quoted from Ebay ^^  >> thats still wrong as i have tested those before and i know its 12AMP fact on a 45mm Plain prop.

This mean this motor requires a 20 amp ESC MINIMUM>> however

I've run 600 motors on 20 amps and still burnt them out!! >>> that motor i would not run on a ESC less that rated for 30 amps! > all these specs motors give never take a LOAD Amperage on running. (nor do they calculate for STALL Amp draw > which is why u burn stuff out .. one weed hooking up the prop say bye bye to that esc if u dont have enough amps to cope with the extra load) 

its always ' ideal loads' on specs math sheets.. come real world application throw that crap out the window and take some old advice.

So with that motor you require this ...

https://www.mtroniks.net/prod/Boat-Speed-Controls/tio-Marine-30.htm

This WILL be more than enough to power that boat for many years with little to no added work ( other than to grease the shaft once in a while) Mtronics are good ESC's they dont have many issues. they can handle NHMI's and lead acid batterys easy... THis is what i have used COUNTLES times in many boats over the years until i swapped to brushless...

i hope that clears things up  

RR

Got a 15A unit as vendor said would be fine. Can also fuse. 

fusing can be a good solution to tht problem, i generally dont fuse my boats however i do have one i had too wince it has 3 motors , the fuse box was actully the easiest way to wire up 3 motors ESC's rather than making harnesses. funny cos that boat is the least problomatic of my collection, however when a fluse blows its a god damit moment trying to find which one of the 4 it is!

i hope the 15 amp works out... tht would not have been my first choice on size 15amps generally i wouldnt use on anything bigger than a 540 becuase of the start up loads and stall currents ...

  I do overkill in one move and then next pinch pennies! At least I took radio advice and got cheap but tough HK unit. Now let's see how many foot pounds of torque to turn rudder??

A good 15 or 20kgm will do the job fine for rudders, I tend to do metal geared ones to avoid shredding the plastic gears just out of habit. Try to avoid the digital ones they tend to be problematic if your not running a full digital set.. also they require a steady 6v to run which most esc’s BECs do not provide believe it or not!!! (Most escs claim 6v but it’s closer to 4.5-5v) analogs tend to also have less twitching when range or low power starts, digital a just stop when the powers too low.

So if servo needs more how do you supply it or instead find servo w lower power demand?  It would seem for a given voltage the makers would vary motor size or gear ratios to change torque output. I did find a nice pdf for boat wiring so that's a big help. The quest is THE QUEST!

Most servos are regulated through the reciver at 5-6v larger servos can draw more milliamperes but never more voltage. Depending how u wire up and which battery u want to use, will depend on what you do about servo power. Personally on larger models (3foot and over) I use a lead acid 6v to power the reciver and servo ( this way no loss of control should the motor and esc power run dry since I don’t always pay attention) drift control with no motor is very handy for recovery efforts. The motors/escs are powered directly with a separate more suitable power supply, you simply disconnect the BEC wire in the esc harness to stop the esc supplying voltage to the receiver and servo. ( central wire usualy) the 6v is plugged into the receivers 2 pin power socket, with a switch. You wouldn’t need to fuse it, lead acids are known for under supplying voltage not over.  And there you have it, constant ( and months power for your reciver and servo cos lead acids last ages).

You can of course do it with a 4 aa 6v pack or receiver battery. But if you have a boat with space inside and requires ballest then Why not use an extra lead acid battery to do two birds with one stone?

I intend to use 2 SLAs of 7, 9, or 12A as they will fit in the wood boxes molded into the hull. Haven't tried calculating run time but even the 7s should last a while.