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Discussion Starter · #1 ·
I am in the process of building my first kit loco, a LMS tank loco by DJH. It uses the traditional live chassie for one side and wheel rubs for the other side. How well will this work for DCC? What do other people use to combat the greater risk of shorting out the decoder?

Thanks,

Rob
 

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If you can get the right type of Romfords from someone like Mainly Trains, I'd be inclined to play safe and use insulated wheels all round , with a dead chassis and pick ups both sides. Should only cost a few pounds extra.
 

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on split frame chassis type locos the use of insulating sleeves is highly reccommended as long as all the wires are completely sleeved and cannot touch the frame it should be straightforward
 

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insulated drivers are a must, and if you find the odd spot where you get a short a coating of super glue will prevent shorts. I've given up on kit built loco's, there are just too many areas where short can develop.
 

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Having built about 40 kit locos for DCC and converted many brass locos to DCC I'll chuck my two bob's worth in. DJH in the past supplied Romford wheels with their kits and they now offer them as seperate item. Romfords are insulated at the tyre, Bachmann wheels use an insulated spacer between the axle and wheel and Hornby use a plastic center. If DJH have supplied a pickup wiper strip for the opposite side then they'll be no problem. If they haven't then you'll have to make your own. I do this using sleeper PCB strip by stripping the copper off one side and superglueing the strip to the chassis. I then solder appropriate shaped phospher bronze wipers in place arranged to rub on the back of the tyre. If it looks like the wiper can contact the live chassis I glue a piece of 5thou plasticard to the face of the chassis. Most shorts come from the likes of the brake shoes so care must be taken to ensure the shoes don't touch the the insulated tyre. Also check that the the arm of the shoe or however it is mounted can't touch the insulated wheels. Where possible use a modern can motor like a Mashima that uses an insulated brush holder as it eases the work load using a motor that is already insulated from the chassis. If you build a tender engine then the pickup is a little bit different as the power is picked up on one side of the loco and returned via an insulated drawbar on the opposite side of the tender.. In tender locos I usually rearrange the wheels so all the insulated wheels are on one side of the loco and tender then I add pickup wipers in a similar fashion to the loco and tender. I usually will mount the decoder in the tender as it has the most space and just run the wires back to suitable micro pin connecters. If I'm fitting sound I use the same method.

Ozzie21

QUOTE (80class @ 21 Sep 2006, 05:00) <{POST_SNAPBACK}>I am in the process of building my first kit loco, a LMS tank loco by DJH. It uses the traditional live chassie for one side and wheel rubs for the other side. How well will this work for DCC? What do other people use to combat the greater risk of shorting out the decoder?

Thanks,

Rob
 

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QUOTE (80class @ 20 Sep 2006, 20:00) <{POST_SNAPBACK}>What do other people use to combat the greater risk of shorting out the decoder?

I don't understand the relevance of wheels and pickups. These are on the input side of the decoder. Any shorts between wheels and frames will cause the booster to shutdown but will not damage the decoder.

The only place you can "short out the decoder" is on the output connections to the motor or lighting. If the decoder isn't shrink wrapped then insulate it with heatshrink if the instructions allow this, or sit it in a tray of plasticard to prevent it touching any live parts of the chassis. The motor brushes MUST be isolated from the chassis. Use heatshrink over the connections if you think there's a risk.

Andrew
 

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All very true but when a newbie sees the word "short" with DCC they almost all think expensive factory smoke. True the command station will see a short and the short circuit prortection will become active but with some command stations this will reset autiomatically every 30 seconds or so. Do this often enough and the decoder's thermal overload may operate which may need you to power down for 10 seconds or so. Small shorts are annoying especially in kit built locos with etched brass brake gear so all it needs is extra care when building to avoid these annoying shorts and a stop start loco. Quite simple really.

Ozzie21

QUOTE (SPROGman @ 22 Sep 2006, 18:06) <{POST_SNAPBACK}>I don't understand the relevance of wheels and pickups. These are on the input side of the decoder. Any shorts between wheels and frames will cause the booster to shutdown but will not damage the decoder.

The only place you can "short out the decoder" is on the output connections to the motor or lighting. If the decoder isn't shrink wrapped then insulate it with heatshrink if the instructions allow this, or sit it in a tray of plasticard to prevent it touching any live parts of the chassis. The motor brushes MUST be isolated from the chassis. Use heatshrink over the connections if you think there's a risk.

Andrew
 

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Discussion Starter · #8 ·
Thanks for your help everyone, I have now completed the chassis and it is working well with a TCS T1. In the end I built the chassis exactly as the instructions advised only I increased the distance between the wheels and the brake shoes slightly and added small amounts of plasticard to the insulated wheel side. Everything seems to be working happily with no booster shuts down as yet. I really should have mentioned that although new to kit building loco, I have been using DCC for 5 years or so now, and despite the poor wording in my original post, I do know the difference between trackside and motor side shorts. The main problem with DCC for the masses has to be the language barrier! Although being a mechanical and electrical engineer, I'm off to the corner to hang my head in shame...

Thanks again,

Rob
 
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