The Mill

[Donw]

Chris the use of a lower voltage motor is not usually a problem. It depends a bit on the type of controller you use. Something like an emitter follower circuit where the output voltage is controlled will only give a voltage based on the setting. so set half way up it would probably give about 6 or 7 volts. Just don't give it full wack if it stalls or at least only a quick burst of full power. If you are using a pulse width type where the motor is receiving full power pulses there may be a tendncy for overheating. The power should average out but the lower emf will means higher currents each pulse.  Again beware if it stalls dont leave the power on too long.

Just remember under stall condition there is no back emf so with double the volts there will be double the stall current but as the heating effect is proportional to the current squared it is not good. As long as the wheels can slip with the loco against the buffers it would be alright.

 

Don

[Chris-GNR]

Evening Don

 

Thanks for your very informative response.

 

The loco runs on DCC control, a DigiTracks system. I'm not sure how/if that effects things.

 

Cheers

Chris

[BWsTrains]

Evening

 

We had a great time at RailEx over the weekend with the layout & as Jason has said above we were very pleased to receive quite so much interest & have  a lot questions regards the layout.

 

Overall the layout ran well the whole weekend with only one incident of note. Late on Saturday afternoon one of the Tortoise motors looked to have failed it would still throw the blades fully each way but there was a dead spot in the track between the slip & loading shed when it was set to that route. After a bit of investigation looking for loose wires, head scratching, swearing & then starting to prepare to just change out the offending motor it was realised that the adjustable fulcrum point for the actuating wire had made its way down (speculating due to the heat inside the sports hall that afternoon) beyond its very lowest intended position & was stopping switch its self from trowing all the way over in one direction. Once this was rectified by simply repositioning the fulcrum point all was back as it should be.

 

The only other thing that occurred was within the first hour or so on Saturday morning the Neilson started to show signs of poor running & would short out over various bits of track work. So it was taken off the layout & I started to look into what the fault could be. After removing the body & checking for anything obvious such as misaligned pickups or brake gear making intermittent contact with the wheels etc I discovered that the back end of the motor had nearly fully broken away from the main body of the motor!!! This is something I've not sceen or heard of before. Its amazing to think that the motor & loco had ran at all.

 

This is the offending Mashima. The screwdriver is wedged in just to highlight the location & extent of the damage.

 

IMG_0192.jpg

 

I had brought along a couple of motors just to show to a few people these being a couple of square 6pole motors available extremely cheaply on eBay.

One is 10mm square x 15mm in length & the other is 15mm square x 18mm. The one used as a replacement in the Neilson is the 10mm one & it is really powerful & torque-ee (is that a word? I doubt it) for its diminutive size. The mounting screws alined perfectly with the Highlevel gearbox re-using the M1.5 screws from the dead Mashima. A downside is that the shaft is only 1mm diameter so I made up a sleeve to allow it to fit the 1.5mm diameter worm. The other negative is that the top end of the motors rating is at 7.2v so not perfect for 4mm locos on a whole but the Neilson never runs at high speed & certainly isn't romping round & round a big tail chaser of a layout. While not being an expert I wouldn't think the motor is ever pulling a full 12v. I'm sure there might be some electrical wizards (who are experts) out there screaming no(!) but it ran the rest of the day & all day Sunday with no issues whatsoever, the quality of the running being equal to when i'd first built it. 

 

This is the 10mm motor fitted in place of the knackered (technical term) Mashima.

IMG_0193.jpg

 

The two motors mentioned above. The larger one is 15mm square x 18mm has a 2mm diameter shaft & is 12v so a contender for medium/large 4mm locos.

IMG_0194.jpg

 

 

Thanks to all of the people that made it to RailEx & stopped by the layout.

 

Cheers

Chris

I'm no expert but a friend advised me to wire in a pair of diodes (one for each voltage polarity) to drop the input voltage about 0.7V for a can motor (7V rating) I was using to replace a clapped out Ringfield in a IC 125. It is on a DCC layout.

Worked a treat, in my case I needed 2 in each direction to drop the input by `1.5V for best results.

 

Maybe Donw can follow on from his #976 post above and add more technical insight but I can confirm that for any given controller setting, the running speed was reduced quite noticeably with one diode pair installed. With 2 diode pairs the loco speed profile was comparable with the original motor

 

Old diodes can be pulled out of lots of devices like voltage regulators I believe. Voltage drop is fairly standard.

 

Colin

Edited May 29, 2018 by BWsTrains

[Mark Forrest]

Evening Don

 

Thanks for your very informative response.

 

The loco runs on DCC control, a DigiTracks system. I'm not sure how/if that effects things.

 

Cheers

Chris

With DCC you can adjust CV settings to limit the top speed. I assume it does this my limiting the max voltage the decoder sends to the motor. Not sure which CV values you need to change though, I do all mine using Decoder Pro and a Sprog device, so I just go to the relevant tab in the user interface rather than have to remember numbers

[Oldddudders]

With DCC you can adjust CV settings to limit the top speed. I assume it does this my limiting the max voltage the decoder sends to the motor. Not sure which CV values you need to change though, I do all mine using Decoder Pro and a Sprog device, so I just go to the relevant tab in the user interface rather than have to remember numbers

CV 5 limits top speed. Having talked to Chris and Jason on Sunday, their Digitrax DT4xx throttle will easily permit adjustment, including while the loco is moving, using Po setting.

[Jason T]

The Digitrax system has three settings for (what I presume to be) voltage, handily labelled N, OO and O. We only ever use the ‘N’ setting (same on Bacup). Do any knowledgable people know if I am right about the voltage and whether this would negate Chris having to alter any CV’s or add electrickery to his Neilson?

[Donw]

Basically Chris the advice I gave above to be careful if the loco stalls will still apply with DCC.  The ideas of adding diodes would help as the voltage reduction would be their under all circumstances. diodes are fairly small so you could find room.

My understanding of DCC decoders is that the modern ones use what is known as an H bridge circuit to supply pulses to the motor but that the frequency of the pulses is not the 50Hz but more like 20kHz which means the motor behaves more like it was a steady voltage at the average of the pulses. They also feature back EMF feedback boosting the power if the detected back emf drops. The CV5 to limit top speed would probably adjust the pulses to reduce the maximum average voltage. So I would reduce CV5 a little. I cannot say whether the decoder will adjust the output so the reduced max is spread across all all the speed steps or whether it just stops the higher steps increasing the the output. It probably depends on the decoder. If it is  the reduced output spread across all the steps if should offer a better control.

 

One of the factors influencing the type of controller is the problems of dissipating excess power. Any controller that works by reducing the voltage applied to the motor will need to dissipate some power itself. Say you have a 12v  supply and the motor is drawing 1A if you want to run it at half speed you drop the voltage to around 6volts. The motor is taking 6 watts but the supply is 12 watts  which means the contoller has to lose the other 6 watts which is why some controllers can get warm. However if instead of dropping the voltage you switch the power on and off so the motor is receiving the power half of the time the supply is then half the 12watts giving the 6watts average that the motor wants and minimal power needs to be dissipated in the controller. For a decoder losing the extra wattage would be a real problem hence the use of a pulse type control.

 

I hope this helps.

 

Don 

[Oldddudders]

When I first bought Digitrax kit 21 years ago, the manual recommended using the N gauge setting, even for HO. I have done so ever since, and have never suffered a motor failure due to overheating in normal use. I suggest a bit of trial running and testing of motor temperature will soon indicate distress. Furthermore, the Mill layout design guarantees motors are never running for very long, nor at full-belt. Scalextric it ain’t!

[Jason T]

Very true Ian, and the longest a loco is used is thirty minutes (and that is only if we tie ourselves in knots with the shunting- easily done).

 

On another note, a video including the layout appeared on the Railex thread, unfortunately featuring the 48DS on Sunday morning when it was behaving badly (due to an unbelievable buildup of crud on the pickups). I would hate for anyone to think that this is how the loco or layout usually perform as other than that, it behaved impeccably all weekend.

[Donw]

Very true Ian, and the longest a loco is used is thirty minutes (and that is only if we tie ourselves in knots with the shunting- easily done).

 

On another note, a video including the layout appeared on the Railex thread, unfortunately featuring the 48DS on Sunday morning when it was behaving badly (due to an unbelievable buildup of crud on the pickups). I would hate for anyone to think that this is how the loco or layout usually perform as other than that, it behaved impeccably all weekend.

 

The 48DS must be a celebrity they always seem to have a camera trained on them when they make a slip up. 

 

Don

[Chris-GNR]

Thanks again Don for some more comprehensive info regards using these types of lower voltage motors on a 12v supply.

 

I'd be keen to try installing some diodes just to be on the safe side. Would you have any recommendations of the right values i should try?

 

Cheers

Chris

[Donw]

Thanks again Don for some more comprehensive info regards using these types of lower voltage motors on a 12v supply.

 

I'd be keen to try installing some diodes just to be on the safe side. Would you have any recommendations of the right values i should try?

 

Cheers

Chris

 

I would use IN4001 diodes forward current up to 1A reverse voltage up to 50 volt Amazon have these listed 100 for 71p.  IN40007 could also be used these are 1A reverse voltage 1000v . your loco should be drawing less than 0.5A . At same 0.3A each diode would be dissipating about a quarter of a watt so about 1watt in total so I would not wrap them in insulating tape so the heat could escape.

 

Don

[PeterBB]

Late on posting but Chris and Jason - at last I got to see The Mill.

 

Having followed its progress and especially the 600 plus windows and the quality of the Wills walls matching it was truly magnificent.

 

Thanks cheers, Peter

[Jason T]

It’s been a while but the layout was out on Sunday 14th, at a get-together in the Trough of Bowland. Surprisingly, given that it was four months since it last saw power, I had trouble free running all day. Only one photo but I kind of like it.

[davefrk]

Hurrah he's back, we've all missed you Jason. Yer ears must have been burning on a certain weekend in September.... Just ask Chris.

 

I like the photo too.

 

All the best,

 

Dave Franks.

[Jason T]

I was moving house that weekend; you could have been shouting in my ear and I wouldn’t have noticed!

 

Resident of Chester now, in case anyone was curious.

[dhjgreen]

It’s been a while but the layout was out on Sunday 14th, at a get-together in the Trough of Bowland. Surprisingly, given that it was four months since it last saw power, I had trouble free running all day. Only one photo but I kind of like it.

Jason was in disguise, no baseball cap!

 

The layout was captivating as always.

[davefrk]

I was moving house that weekend; you could have been shouting in my ear and I wouldn’t have noticed!

 

Resident of Chester now, in case anyone was curious.

 

Well burger me....

 

You certainly move quick, local constabulary was it.

 

Dave Franks.

[Jason T]

Heads up folks, The Mill is in the April 2021 issue of BRM.

 

[Donw]

44 minutes ago, Jason T said:

Heads up folks, The Mill is in the April 2021 issue of BRM.

 

 

Well deserved.

 

Don

[Jason T]

Thanks Don. Pulling the article together and searching through photos has rekindled my interest somewhat; I actually progressed a couple of wagon kits that had been sat on a shelf for far too long.

[Donw]

I like the way the figures are grouped in the photo much more natural to have a group hanging about than individuals.

 

Don

[Oldddudders]

Good to see you posting again, Jason. Loved seeing this at Railex.

[Enterprisingwestern]

2 hours ago, Oldddudders said:

 Loved seeing this at Railex.

 

What was that then?!!

 

Mike.

[TheSignalEngineer]

3 hours ago, Oldddudders said:

Good to see you posting again, Jason

I saw The Mill a couple of years ago and it looked very good.

I was only thinking last week we hadn't heard from Jason recently. He's too good to be in hiding his talents but I well remember trying to fit in modelling with all the other commitments at his age.