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[mudway]

I've noticed that some friends who are into park fliers and indoor aircraft use some very nice little motors and gearboxes which would work well in our hobby. The catch being that the escs they use are forward only. Has anyone come across any small escs for these have reverse?

[essex2visuvesi]

yep.... see here
http://www.hobbyking.com/hobbyking/store/__23766__HobbyKing_Brushless_Car_ESC_10A_w_Reverse.html

[mudway]

Thanks.
But that is for a brushless motor not a brushed motor like these.
All the normal escs like Mtroniks or Action output between 4.8 and 12 volts depending on the battery input. 4.5 volts might either kill the motor or strip the gears.

[essex2visuvesi]

Ah right..... I did find a brushed one last year when I wanted one for a project.. can't find it now.  I'll have another look in the morning

[inertia]

Thanks.
All the normal escs like Mtroniks or Action output between 4.8 and 12 volts depending on the battery input. 4.5 volts might either kill the motor or strip the gears.

'Fraid you're wrong. ACTion P78/79/80/81 will all handle motor voltage down to 2v.
http://www.action-electronics.co.uk/speed.php
DM

[mudway]

True but for a model 10" long for which these small motors are ideal for, they are way too big & heavy. 

[Subculture]

I know of some very small reversible brushed controllers that work with 6 volts or more- http://shop.strato.de/epages/61433551.sf/de_DE/?ObjectPath=/Shops/61433551/Products/CTI4

Smaller voltages is very specialist, but the cheapest solution would be to buy some 9-10gram servos from hobbyking, which will cost about £3-4, and mod the circuit boards out of them.

[kmmbcwebmaster]

There is a seller on fleabay called mrrcworld he does a 2amp miniture speed controller

[inertia]

Your problem with a model that small is to get a receiver which will operate down at that voltage. Normally a receiver runs from at least four cells (4.8v). A BEC-powered receiver needs at least a 5.5v motor supply while a direct ESC such as the ACTion P68 (which weighs 9g without its case) operates on four cells to power both receiver and motor. It may be possible to run one of these on three or even two cells. If I can find one kicking around I'll try it and let you know.
Dave M

[Subculture]

Most modern receivers run happily on a single lipo (3.7 volts).

[mudway]

Your problem with a model that small is to get a receiver which will operate down at that voltage. Normally a receiver runs from at least four cells (4.8v). A BEC-powered receiver needs at least a 5.5v motor supply while a direct ESC such as the ACTion P68 (which weighs 9g without its case) operates on four cells to power both receiver and motor. It may be possible to run one of these on three or even two cells. If I can find one kicking around I'll try it and let you know.
Dave M

I was going to use one of your P68As (assuming you are who I think you are) but did a test this afternoon and found that on 4.8 volts, the little beast pulls .95A in the water. Far too close for my liking to the rated 1A of them. That was on an approximately 14mm prop. The prop started the day at 18mm but was slowly filed down to try & bring the amp it pulled down to something reasonable.
 
The geared motor came out of a little indoor flyer toy which finally went to God when a friend’s dog decided to catch it when it was landing. So I acquired the motor etc. It seemed to have an all in one receiver and esc and ran off a 3.7 volt battery.  Came with its own 2.4 GHz transmitter. Actually not bad for about 15 quid.  Part of me is tempted to buy one and cannibalise it except I do like the idea of reverse on my models. Does help when someone just wanders across the front of your bows.
The other thought is to see what happens when I plug the 3.7 volt battery into the receiver with the P68A too and see what happens. I'll have to replace the plug on it as it is a strange little thing which I have never seen before.
 

[malcolmfrary]

Most modern receivers run happily on a single lipo (3.7 volts).

A lot of modern gear has electronics that work more or less OK down to a surprisingly low voltage.  The real questions are whether the voltage supply is stable enough under load because the electronics relies more on stability than actual voltage.  Whether other items, like servos, will be responsive enough, or in the case of ESCs, whether the output stage will saturate enough to avoid heating under load is another consideration.
The "standard" used to hover around 6 volts - handy for the batteries of the day, being 3 lead acid cells, 4 dry cells or 5 NiCads.  The advent of digital integrated circuits settled on a very closely regulated 5 volts, which is now largely the new standard.  Lithium batteries are either well below this, or considerably higher, which leaves a problem.  Later generations of static logic chips had a much more generous operating voltage spread, active chips like PICs less so.  The logic part of most of our gear is probably happy down to 3 volts, possibly less.  This leaves the problems of the output stages not switching fully and cooking themselves, and voltage stability under load at a low starting voltage.
The answer in this case, space and weight considerations being met, might be a home made mini Bobs Board - a mini servo working a wiper to switch resistors.

[mudway]

 Well I did a little test over the weekend and dropped the motor into an 18” hull I already have running and gave it a whirl.  It went like stink getting it up onto the plane at 4.8 volts. The downside was playing catch as I had no speed controller in it so that was the only way of stopping it. Also, the noise. Sounds like a gas turbine screaming its head off. Now to get my hands on a 3.7 volt battery and see if the Action esc will handle it. If not, I’ll try it with the non reversing aircraft esc it came with.

[inertia]

So did I.
I connected a Planet T5 Rx to a 3.0v regulated bench power supply, a Hitec HS81 servo, an ACTion P68A ESC and a micro-cassette motor (rated up to 5v). It worked perfectly with no glitches or other sign of instability. As such it will certainly work on a single LiPo cell (3.7v).
P68A is available from Component-Shop. 
Dave M

[mudway]

Thanks Dave,  I've ordered some AA sized 3.7v 900mah Lithium Ion batteries off ebay, so the test beast will shortly run with a P68A.  I have a few in stock.

[inertia]

Splendid. Do post your results here.
Dave M

[essex2visuvesi]

Just to post some of my findings re using electronics on a single cell lipo


Spektrum receivers (SR301) are not happy on a single cell lipo.  while it will work as soon as the battery drains a little it will "brownout" causing loss of control for a few seconds

[mudway]

Hoping to get my batteries by the weekend, so I can find out if the theory works.
My Spektrum is now back in the box & I'll try a Hobby King one or an old 27 meg radio, all with a P68A.

[essex2visuvesi]

Hoping to get my batteries by the weekend, so I can find out if the theory works.My Spektrum is now back in the box & I'll try a Hobby King one or an old 27 meg radio, all with a P68A.

 
 don't write off the spektrum tx. There is an orange receiver on hobbyking designed specifically for single cell lipos. I'm on my phone right now will post a link later

[mudway]

Haven't got my batteries yet but a friend uses the orange receivers in his boats. Will have to presuade him to come over some time with the transmitter and a spare bound receiver.

[essex2visuvesi]

 
 don't write off the spektrum tx. There is an orange receiver on hobbyking designed specifically for single cell lipos. I'm on my phone right now will post a link later

Here's the rx I was talking about
http://www.hobbyking.com/hobbyking/store/__18827__OrangeRx_R415_Spektrum_DSM2_Compatible_4Ch_Micro_2_4Ghz_Receiver.html


slight snag is the connectors, but HK do suitable micro servos to that fit

[mudway]

Have got my batteries and the normal 2.4ghz Hobby King V2 receiver seems to work OK on 3.7 volts as does the Action P52.
Walked off over 100 foot & it still worked, by then the boat was a speck in the distance.  With a 14mm cut down Deans Marine 18mm prop, consumption is .6 amp and with a full 18mm prop it is still only .75 amp, so no problems with killing the Action esc.
So a 3 volt speed controller is no longer needed. Now to play with my little toy.

[inertia]

Just as an aside, both the P52 (now discontinued) and the P68A have automatic shut-down if the current exceeds 1A; you won't kill them that easily.
DM

[mudway]

Thanks, the P52 came out of a model & is still working happily. When was it discontinued?

[inertia]

Probably about two years ago when we ran out of PCBs. I decided that it didn't warrant buying another 100 boards for sales of about ten units a year, especially when P68A did the same job but smaller.
DM