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[SimonCornes]

I've already asked for advice on a Model Slipway Trent that I have recently acquired in the Lifeboat section but maybe a more generic answer is what I need? The boat has a pair of brushed motors each fitted to a Model Slipway belt reduction adaptor which I believe is 2.3:1 No speed controllers or batteries. I have a  Component Shop P94 ESC/mixer which can take 20 amps per motor. I also have CS P95 'indicator' fuse units fitted with 15amp fuses.


I tried to run the set up on the bench for the first time yesterday with a single 3S LiPo. I got through half a dozen fuses ! Today I bought 10 more 15A fuses. I thought that the P94 or fuse boards might be faulty as only the left fuse was blown. I then discovered that one of the spade connectors on the right motor wasn't properly connected and, now that it is, the fuse on that size blows well to!


Eventually I disconnected the motor leads and attached a pair to my voltmeter. This showed that the P94 and P95's are all working properly and smoothly, albeit one seems to lag behind the other (not sure if you can adjust the P94?) and mixing properly with rudder inputs.


So the problem must be the motors pulling too many amps.
It's has been suggested that I replace the motors with the brushless variety but this boat must have worked okay with the previous owner with the existing set up.
Do I ditch my P94 and P95's and get hold of a pair of Perkins 50A ESC's and forget about motor/steering mixing? I use a RadioLink system and I don't think that, amongst its myriad of clever and confusing instructions, there's anything that could mix channel 1 with 3 and 4!


I'd really be interested in your suggestions. The real boat can do 25 knots so no slouch - but not that fast - but I don't want my boat to crawl along at a scale 15 knots only as that would be a bit sad!

[NickelBelter]

Pictures of the model, particularly the motors and belt drive setup, would be very helpful here.

[Abandon Ship]

You don't mention what motors are fitted or how long the boat may have been in storage.
If it were me, I'd disconnect the motor power and drive belts and check the motors spin freely by hand. If they seem OK, then one at a time power them directly from a lower voltage/low current source such as a 4xAA holder with standard alkaline cells. Add an inline fuse if using li-po or other rechargeable battery. The motors should run smoothly and quietly - if not they could be the issue.
If all that works reconnect the electrics (but not the belts) and try running with a 6v source or 2S li-po. This should help prove the ESC is OK.
Next check the belts are still flexible and the prop shafts run free. If it's been standing for a while, there could be sticky oil/grease or rust causing binding and increasing current draw.


hopefully these checks will help you track down the issue.

[SimonCornes]

Thank you for your replies. Having established that the ESC seems to be fine, today I connected each motor to my mains power supply unit and ran each monitor on up to 6v DC. Each motor seemed to accelerate well starting at 0 volts (where each motor still turned!) but after maybe 15-20 seconds the revs started to drop until each motor stopped. I had previously been advised to remove the 3 suppressor capacitors from each motor in case one of those was causing a dead short so they all came off.
I removed each motor. They are both Johnsons - 65mm can length, 38mm diameter, 25mm between the securing screw centres and a 3.36mm shaft. I imagine that these are basically standard 600 size motors? I removed the belt drive gear from each and both armatures turn freely enough but maybe the brushes are worn out?

I'm thinking that the easiest thing to do is to buy a pair of 600 size motors. I don't want brushless if I can help it but I have no idea where to go for a decent pair of motors that will give a reasonable performance for a 1/16th lifeboat?
Any suggestions of 'what' and 'from where' please?

 

[Abandon Ship]

Glad to see you're making progress. I don't know your specific model so can't recommend a motor spec, but I would suggest that motors that fit your mountings and pulleys would save some reworking of the interior.
You might want to double check the motor shaft diameter, I believe 1/8" (3.175mm) is more common.

[HMS Invisible]

Thank you for your replies. Having established that the ESC seems to be fine, today I connected each motor to my mains power supply unit and ran each monitor on up to 6v DC. Each motor seemed to accelerate well starting at 0 volts (where each motor still turned!) but after maybe 15-20 seconds the revs started to drop until each motor stopped. I had previously been advised to remove the 3 suppressor capacitors from each motor in case one of those was causing a dead short so they all came off.
I removed each motor. They are both Johnsons - 65mm can length, 38mm diameter, 25mm between the securing screw centres and a 3.36mm shaft. I imagine that these are basically standard 600 size motors? I removed the belt drive gear from each and both armatures turn freely enough but maybe the brushes are worn out?

I'm thinking that the easiest thing to do is to buy a pair of 600 size motors. I don't want brushless if I can help it but I have no idea where to go for a decent pair of motors that will give a reasonable performance for a 1/16th lifeboat?
Any suggestions of 'what' and 'from where' please?

They're absolutely fine!
And will be 3.175" shaft & M3 @ 1"/(25.4mm)

[SimonCornes]

Thank you for your reply but can you recommend a suitable alternative motor please as these Johnson’s are shot!!
Thanks

[HMS Invisible]

555 motors are not a drop in replacement, but I'd have recommended them to start with. They would need a minimum of 12 volts & up to 4s and they'd replace 600 motor and reduction, if the props are already matched.
Despite what you said over two threads, I don't believe there is anything wrong with the motors. What happened with the 15 amp blade fuses and power supply is in line with what I'd expect.

[SimonCornes]

Thanks for the prompt reply. I know what you mean about 555's but I want to stick with 600 size motors via the reduction belts as they are Model Slipway units and so the boat should work as designed. It would be considerable hassle to me to rip out the existing mounts so its easier to go with replacements but I'm not sure what the best alternative is for a Johnson or a Graupner Speed 600 these days or the best source?


I'm not sure why you think the Johnson's are okay? In my book something is getting hot very quickly and causing both motors to stop, even off load?
I wonder if they've previously been over volted causing internal damage or if the brushes are basically worn out?

[HMS Invisible]

If you can get hold of a RE540/1, to run on 12v, then it would nearly
replace a 6v 600/540 in the belt drive.
 I used to supply suitable fuses and holders with escs and give away like sweets, but they were 30mm anti surge fuses, and for the main supply, to prevent damage to wiring. For motors I supplied and gave away resettable polyswitches. If I was ever asked for my opinion on automotive blade fuses to the motor, I would have said the notion was crackers.
 I nearly asked what mains psu that you had, at the first mention. Anything less than the 300 Watt switching type in the photo has no chance of driving a lightly loaded, low turn dc magnet motor in 500/600 size.

[SimonCornes]

Thank you. I see Component shop sell MFA RE540/1 motors so thats a source although I would normally avoid 3 pole motors like the plague!
As it stands I've just bought a pair of Johnson 683's from Howes as they are a very similar physical size and they were cheap! May not be the ideal solution but worth taking a flyer!

[Abandon Ship]

Those 683's can pull around 15A each on 3S. As you're using 15A fuses, I would recommend you start with 2S to keep the current down. Or buy a big box of fuses and get used to changing them!

[HMS Invisible]

The 683 spec and description. 
24 watt loss with a shaft mounted fan at 20,000 rpm is going to run cool, relatively speaking.
It's more of the same as what you have in situ, and you'll see.

If you splashed out on a random selection of motors, from whatever source, you'd soonest find a use for things like 555 motors, 540LN. Brushless is better for high power and high rpm in boat models where these "drill" motors have once been used.

You can get sensored and sensorless brushess 500/600 combo replacements to experiment with but do you want to replace the speed controls?

[SimonCornes]

No, the last thing I want to do is replace the P94. I could have just fitted a pair of 50A Perkins ESC’s and separate batteries but I had a P94 and I know they work well. That’s why I didn’t want to go to the expense of a pair of brushless motors with ESC’s. Of course  I ultimately may have to but I want to try this boat as designed. I’ve got a set of the Model Slipway drawings and I see it was intended to have straight drive Graupner Speed 600’s so I don’t know his many were built with with Model Slipway reduction belt drives. The drawing also shows 5 sub C type cells although was that two sets of 5, 1 set each side of the centreline and were 2 sets wired in series or parallel? I have no idea what was the ‘best practice’ when the kit was new.

[pipster]

Hi SimonI've got a 1/16 MS Trent and I've dug out the manual.  The recommended motor set up was Graupner Speed 600 ECO (straight drive, no gears) and 2 NiMH 9.6v battery packs.  That's how I ran mine orginally before converting to brushless.  I think it had a reasonable turn of speed but fairly short run times.
Cornwall Model Boats stock Speed 600s thhough I don't how what the difference is between Speed 600 and Speed 600 ECOs.  They're usually pretty helpful if you call them for advice.
Phil

[SimonCornes]

Thank you Phil

[NickelBelter]

Thank you for your replies. Having established that the ESC seems to be fine, today I connected each motor to my mains power supply unit and ran each monitor on up to 6v DC. Each motor seemed to accelerate well starting at 0 volts (where each motor still turned!) but after maybe 15-20 seconds the revs started to drop until each motor stopped. I had previously been advised to remove the 3 suppressor capacitors from each motor in case one of those was causing a dead short so they all came off.
I removed each motor. They are both Johnsons - 65mm can length, 38mm diameter, 25mm between the securing screw centres and a 3.36mm shaft. I imagine that these are basically standard 600 size motors? I removed the belt drive gear from each and both armatures turn freely enough but maybe the brushes are worn out?

I'm thinking that the easiest thing to do is to buy a pair of 600 size motors. I don't want brushless if I can help it but I have no idea where to go for a decent pair of motors that will give a reasonable performance for a 1/16th lifeboat?
Any suggestions of 'what' and 'from where' please?

So you ran each motor off 6v while it was connected to the belt reduction drive and propshaft?  And after 15-20 seconds the motors died all on their own (ie. they did not trip an overload protection device in your DC supply)?  It definitely sounds like the motors are bad, assuming that you checked the shafts for binding/drag. 

[HMS Invisible]

...And after 15-20 seconds the motors died all on their own (ie. they did not trip an overload protection device in your DC supply)?...

...& with no improvised trip indicator,  Simon is none the wiser, so doesn't allow the p.s.u. thermal protection any time to reset.

[SimonCornes]

My PSU is a ‘versatile PSU’ which I think was an electronics project in Model Boats or something like that and I made it myself last century!! There’s a fuse I’m pretty sure but absolutely nothing ‘smart’ about it. I calibrated the DC output using a voltmeter and a pencil to mark the knob position and it has always worked beautifully. As
For the two Johnson motors, I tested them out of the boat so disconnected from the drive belt and both slowed down as mentioned and then stopped. I could turn the power off and back on again and repeat the process with identical results. The two replacement Johnson’s I ordered from Howes should arrive on Monday so my first job will be to run each one via the PSU and I hope the revs don’t drop!! In theory they should be fine but this is black magic so I’m counting nothing out!!

[HMS Invisible]

I'm guessing Maplin magazine project with a variable linear regulator, like the L200. Unless it has a piggyback transistor, any semiconductor regulator will thermally trip seconds after running anything beyond a 55-turn 555 motor.
A resistor & LED combo at the output would have shown such a cutout.

[NickelBelter]

My PSU is a ‘versatile PSU’ which I think was an electronics project in Model Boats or something like that and I made it myself last century!! There’s a fuse I’m pretty sure but absolutely nothing ‘smart’ about it. I calibrated the DC output using a voltmeter and a pencil to mark the knob position and it has always worked beautifully. As
For the two Johnson motors, I tested them out of the boat so disconnected from the drive belt and both slowed down as mentioned and then stopped. I could turn the power off and back on again and repeat the process with identical results. The two replacement Johnson’s I ordered from Howes should arrive on Monday so my first job will be to run each one via the PSU and I hope the revs don’t drop!! In theory they should be fine but this is black magic so I’m counting nothing out!!

Bizarre!  I've never heard of a knackered motor that will run for a little bit, usually when they toast themselves they'll never spin again!  I'm sure the new ones will run just fine as the free-running current for even 'hot' motors is minimal.

[chas]

It is bizarre isn't it, I've never heard of a motor doing that either, let alone two of them, from the same model. What are the chances of that? Of course this could be settled so easily by just checking checking the motors on a known good battery, preferably with a volt and ammeter conected.