End point question

[Neil Powell 1Participant @neilpowell1]

Hi,

I'm looking for a set of motors for my next project. On my last model i used a pair of mtroniks m600's which are rated at 12000rpm at 12v. As they were still too fast i set the end points on my transmitter to 30%. Am i right in saying that the motors will be limited to about 4000rpm?

Also has anyone got any experience of mfa metal gearboxes. Are they reliable and quiet?

Cheers

Neil

[Neil Powell 1Participant @neilpowell1]

[ashley needhamParticipant @ashleyneedham69188]

Hi Neil.

What is the new project? We can’t even begin to advise you if we don’t know what it is,!

Size, weight, hull style, prop size, expected top speed etc etc

Ashley

[Dave MilbournParticipant @davemilbourn48782]

Am i right in saying that the motors will be limited to about 4000rpm?

That presupposes that the ESCs are totally linear in response, whereas in my experience they seldom are. The only way to check is with a tachometer. You're better advised to fit slower motors or use less volts if you need less RPM because it's at the mid-speed range where ESCs get the most hot and bothered.

I've used the geared MFA motors and they most definitely are NOT quiet!

Dave M

[Malcolm FraryParticipant @malcolmfrary95515]

ESCs run coolest at their extremes – fully off, no current, no heat. Fully on, no switching, just creating heat by virtue of component resistance. Anything in between, they are switching on and off several thousand times a second, and it is during the transition time between on and off that they create heat. If they can't get rid of the heat fast enough, they get hotter. And hotter, over time.

Having the right battery, motor and drive train is important. Getting round bad choices by bodging electronically is always second best. Going for a drastic end point reduction will likey result in rough control. Digital stuff works in steps. Closing the end point makes for fewer, but bigger, steps somewhere along the line.

[Charles OatesParticipant @charlesoates31738]

Hi Noel, I might have missed something, but if the model is being overpowered to such a drastic degree, why not just reduce the supply voltage from the 12volts you imply you are using, to 6volts?

Charles

[Neil Powell 1Participant @neilpowell1]

Hi thanks for all the replay. My new model(bait boat) is pretty much a reworking of the last one with some improvements e.g better access to electrics. The size is the same but I'm hoping the weight will be slightly less. I have ordered a tachometer now from eBay so I'll be able to see how much rpm they are running at.

Learn something new everytime I ask a question on here. Never knew that esc's worked harder when in the middle range.

In respect of the suggestion that I use 6v batteries I want to stick with lipo to reduce the weight a bit, could go from 3s to 2s I suppose.

[Dave MilbournParticipant @davemilbourn48782]

Neil

You haven't helped us to suggest motors etc for your next project. Please read Ashley's post again for the information we would need. Saying "it's pretty much a reworking of the last one with some improvements" doesn't get us any further along the path, m'duck.

Dropping from a 3S LiPo pack to a 2S will significantly reduce the motor speed but there's probably some much more suitable motors out there. I wouldn't look at an MTroniks 600 for powering a bait boat, but that's just my personal preference. Some anglers like their bait boats to run very fast to get the bait out there quickly, while others like to creep up slowly and deposit it carefully and precisely.

Dave M

[Neil Powell 1Participant @neilpowell1]

Posted by Dave Milbourn on 22/07/2020 18:05:21:

Neil

You haven't helped us to suggest motors etc for your next project. Please read Ashley's post again for the information we would need. Saying "it's pretty much a reworking of the last one with some improvements" doesn't get us any further along the path, m'duck.

Dropping from a 3S LiPo pack to a 2S will significantly reduce the motor speed but there's probably some much more suitable motors out there. I wouldn't look at an MTroniks 600 for powering a bait boat, but that's just my personal preference. Some anglers like their bait boats to run very fast to get the bait out there quickly, while others like to creep up slowly and deposit it carefully and precisely.

Dave M

Fair point Dave. It will be a twin hull bait boat at 800mm long and 375mm wide. Each hull is 110mm wide. It is plywood construction and should come in at 6kg.

I believe that the mtronik m600's will be running at about 4000rpm and that works just fine on the old boat(same weight and dimensions) and leaves a little spare for when it's windy etc. The props are 50mm twin bladed plastic things on a 5mm shaft.

I was hoping to find a way of running the motors at 4000rpm ish without messing about with the end points. I know people are going to say throttle control but thats easier said than done when you are trying to manage the line on the reels and steer the boat at the same time.

I'm more of a slow and accurate type of bait boater. don't like all that white water coming out the back of the boat and it not really moving any faster.

[Neil Powell 1Participant @neilpowell1]

[Neil Powell 1Participant @neilpowell1]

[Paul TParticipant @pault84577]

Neil

What is the estimated all up weight of your boat when it is fully loaded.

Paul

[Neil Powell 1Participant @neilpowell1]

Posted by Paul T on 22/07/2020 18:39:22:

Neil

What is the estimated all up weight of your boat when it is fully loaded.

Paul

Paul with bait at the most 7kg. The hoppers will take about 5kg but i don't use that much ever

[Paul TParticipant @pault84577]

Neil

I designed a similar bait boat some time ago for a chap who wanted drop 10kg at a time.

I opted for 2 brushless motors each with its own battery.

[Neil Powell 1Participant @neilpowell1]

10kg at a time, he must have been loaded. What was the overall weight of the boat and what motors did you opt for?

[Dave MilbournParticipant @davemilbourn48782]

These wil do the job easily on 12v without undue drain on the batteries or overheating the ESCs. I'd also suggest three or four bladed props. 775 motor

Dave M

[Neil Powell 1Participant @neilpowell1]

Posted by Dave Milbourn on 22/07/2020 22:50:38:

These wil do the job easily on 12v without undue drain on the batteries or overheating the ESCs. I'd also suggest three or four bladed props. 775 motor

Dave M

Thanks Dave. Have you got experience with these? do you know if they run quietly?

[Dave MilbournParticipant @davemilbourn48782]

I have one in my workshop although I've never fitted it into a model. It runs very quietly. The warship brigade are very impressed with them, I gather.

DM

[Malcolm FraryParticipant @malcolmfrary95515]

A trick I did with a stick transmitter with mechanical slide trims and an ESC with a setting button and a bit too much motor was –

Set Neural, stick center, trim full down

Full forward, stick and trim full up

Reverse, stick and trim full down

A test of memory and manual dexterity, but it had some bonuses.

You had the option of setting a gentle cruise speed with the trim being used as an engine room telegraph and stick at center, normal full speed, stick full forward, get out of trouble spedd, everything forward. I wouldn't like to try this with a modern clever radio – even if they let you tweak things on the fly, you need to see the screen, and that means not looking at the boat.

Most electric motors run quietly provided that the bearings are not shot and that they are being operated in their comfort zone.

Gearboxes and poor alignment are the princilpal sources of noise. Direct drive and the right choice of coupler help keep things quiet.

There is usually some motor whistle from the ESC switching at anything other than either full stop or full speed, due to a waveform being presented to a set of coils that can move. Thats pretty much a description of the works inside a loudspeaker, so no real surprises there.

[Paul TParticipant @pault84577]

Neil

The designed all up weight was 14.5kg, the chap was a carp fisherman who wanted to dump 10kg at a time in precisely the same location.

The bait boat was designed to carry this weight and was intended to use drone gps technology to consistently drop the load in exactly the same place.

I found that the brushless motors were to noisy so on Dave Ms advice the spec for the motors was changed to a pair of 775s with 4 blade props.

Paul

[Neil Powell 1Participant @neilpowell1]

Thanks everyone. Tachometer showed by current boat running at 4500 – 5000 rpm at full chat. Pair of 775's, as suggested by DM, on order.

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