DCC and Whitemetal Locos

[6029 King Stephen]

I am building a Millholme Models Merchant Navy loco and plan to use a Mashima 1833 motor mated to a 40:1 gear wheel. However, I also want to fit a decoder but am unsure of whether my normal choice of Hornby R8249 will be sufficient. The kit is becoming heavier and heavier as I proceed with assembly and wondered if this weight would have any bearing on decoder choice?

 

If the Hornby R8249 isn't suitable, please you suggest some reasonably priced alternatives? I won't be fitting any lights or smoke generators to this loco so the decoder doesn't require lots of functions.

 

Thanks,

 

Steve

[Piemanlarger]

i think a better quality one would be the choice, lenz gold would be my starting point.

[Nigelcliffe]

i think a better quality one would be the choice, lenz gold would be my starting point.

From my reading of the Lenz documentation, the Lenz Gold offers no advantages over the Silver unless the PM1 power module is added, or the Susi connectors are to be used to a Dietz sound chip. May as well save some money.

(personally I'd be checking the Zimo range, but the loco is so far away from my normal builds I don't want to make a recommendation).

[34theletterbetweenB&D]

I have had an 18/33 on 40:1 in an 800g 9F, a Lenz Silver worked perfectly; the cheaper Lenz standard that is now available has the same excellent drive, with fewer features. I would expect Zimo MX63 and 64 to work equally well. (This 'gorilla' has now been withdrawn with the advent of the Bachmann model, it was built this way for outdoor operation to cope with gradients and wet rails and is rather OTT for the current layout. One thing to watch out for on the mechanical side, rod wear on the crankpins.)

 

Hopefully it will be a free running mechanism, if it is a similar weight to my 9F it will likely draw something between 150 - 200mA running light: with a train weighing about 6kg on nominally level track it drew 700 +/- 100 mA continuously. Measuring the current draw on DC to ensure you stay within the rating of the decoder is recommended.

[Ron Ron Ron]

From my reading of the Lenz documentation, the Lenz Gold offers no advantages over the Silver unless the PM1 power module is added, or the Susi connectors are to be used to a Dietz sound chip. May as well save some money.

Nigel is right, the Gold+ and Silver+ are essentially the same decoder, apart from the Gold's USP circuit that allows you to add the power-1 storage module and the SUSI interface for installing a piggyback sound chip.

Unless you need these functions, the extra cost of the Gold may be considered wasted money. The drive control is the same for both these decoders and, I understand, the Standard.

 

However, there is one other difference between Gold+ and Silver+ that may be missed.

Although both have 5 function outputs, hidden on the spec. sheets you will see that the Gold's four standard function outputs appear to be rated higher than those of the Silver (200 mA versus 100 mA).

Both appear to have the same 500 mA rated 5th function output.

 

If you are running power hungry lights and accessories (servos etc) on your loco, I suppose the higher rated function outputs may be of benefit.

I'm sure someone better qualified than me in this subject will be able to comment on this?

 

.

[Piemanlarger]

i have not baught a gold or silver lenz chip for several years, what are current prices?

[NoggintheNog]

i have not baught a gold or silver lenz chip for several years, what are current prices?

 

Somewhere in the region of ??30/??25/??20 for Gold/Silver/Standard respectively.

[jazz]

Probably no help to you but I run my 7mm locos up to 2 lbs in weight on my PowerCab with a TC1 decoder (around ??14.00) with no trouble. The locos use Mashima 1833's mated to 40:1 gears. One is a white metal kit and VERY heavy.

[Ravenser]

The T1 handles 1.2A continuous , 2A peak. Its rather higher rated than most decoders, and it's relatively cheap. There's a saving for the wire only harness , so this would be my suggestion for hardwiring a whitemetal kit

[Guest Max Stafford]

I'm planning on fitting decoders to my own kitbuilds. It's almost inevitable that there will be shorts despite my best efforts with all that brake rodding etc down there. I'm going to try the Bachmann jobs out for the simple reason that they'll be cheaper to replace if things go a bit wrong. My power units are generally Mashima 1220s and 1224s driving High level 40:1 Roadrunners or 1424s driving 60:1 Loadhaulers.

 

Dave.

[great northern]

I also use mostly TCS T1's in my kit built stuff. They are indeed somewhat cheaper than the top of the range stuff, and seem to do the job perfectly well. And if you do cook one, there is always the "goof proof" warranty.

[Lady_Ava_Hay]

It is not the decoder you really need to worry about. All white metal kits have one fatal flaw - all are designed to have a live chassis. This is not good. If you buffer up to another kit loco that is DCC'd in reverse polarity then you will short the decoder and blue smoke will result.

 

You will need to invest in all insulated driving wheels and bogie wheels so that the chassis is isolated. Use pick ups on the four main driving wheels and use insulated wires to the decoder which then supplies the motor.

[Guest Max Stafford]

Thanks David. What if you're modelling a six or eight - coupled machine? Obviously the more pick-ups, the merrier as far as performance is concerned, is this a problem for DCC operation? For what it's worth, I already use insulated wheels all round and cover as much of the pick-up wiring as possible using heat-shrink tubing.

 

Dave.

[Nigelcliffe]

In my view, the problems to overcome with metal models are two main areas:

 

a) from wheels to bits of the body when not wanted. Here good clearances and insulation solves the problem.

B) from chassis through to buffers and couplers. This avoids the problem which David White describes where one vehicle shorts out another due to being the wrong way round. ( I don't see how the short which David describes causes blue-smoke, its just shorting one rail to the other, which is the same as a derrailment. It will cause the command station to shut down due to the short ).

 

Coupling rods should not be a problem with plastic centred wheels. They will be insulated, and if correctly mounted with a spacer between wheel and coupling rod there is no way for them to touch the wheel rim. (Insulation can be part of the crankpin or crankpin bush, and if not, just a washer).

 

The other risk area is brake gear, this is often more fragile than coupling rods. The easier solution is to make the brake shoes from an insulator, plastics, paper (soaked in cyno glue), etc..

 

 

Live chassis themselves need not be a problem provided the body can be isolated (it is afterall what happens with split-framed construction where both frames are live to each side rail). Isolation might require some thinking in certain whitemetal kits which had not considered the possibility of a problem, particularly those which use the "American" pickup method of loco live to one rail and tender live to the other.

[Crosland]

It is not the decoder you really need to worry about. All white metal kits have one fatal flaw - all are designed to have a live chassis. This is not good. If you buffer up to another kit loco that is DCC'd in reverse polarity then you will short the decoder and blue smoke will result.

A live chassis is *live to the rails*. If two oppositely wired chassis make contact then you will short the rails and the booster will shutdown. There is no damage to the decoder.

 

Exactly the same argumant applies to DC locos with live chassis.

 

Andrew Crosland

[Lady_Ava_Hay]

Thanks David. What if you're modelling a six or eight - coupled machine? Obviously the more pick-ups, the merrier as far as performance is concerned, is this a problem for DCC operation? For what it's worth, I already use insulated wheels all round and cover as much of the pick-up wiring as possible using heat-shrink tubing.

 

Dave.

 

Absolutely Max, the more pick ups the merrier. On long coupled locos just check that the wheels selected for pick up are actually in contact with the track.

 

As to the shorting by buffers that will ostensibly shut the command station down rather than fry the decoder as Andrew has said, point taken but I think it still applies that putting even momentary very high currents through a decoder is not a good idea.

 

i still think it is bad practice for metal buffered kits to have this sort of design flaw but it is easily fixed by fitting the latest Bachmann sprung types as they are plastic.

 

Again though, another plug for DCC in that kit manufacturers obviously realised that buffering up with DC locos is practically impossible anyway.

[artisan100]

All white metal kits have one fatal flaw - all are designed to have a live chassis.

 

Sorry, can't that let that one pass, David. We at Comet may only have 4 loco kits, but we do have over 40 chassis in our range and we have always recommended using insulated wheels on both sides of the loco. This hasn't always gone down well with customers as it means they need to fit pickups on both sides and until fairly recently the insulated Romford/Markits drivers were more expensive than the uninsulated or 'live' ones, but it does keep the chassis out of the electrical equation. And Gibson wheels, with their plastic centres, automatically give you an electrically dead chassis.

 

Geoff

[Guest Max Stafford]

Would a very thin layer of epoxy on the surface of the buffer head be helpful in reducing any problems here? It's just occurred to me that with a white metal tender a similar problem might exist. Although as I understand it wheelsets are insulated from their axles, so it may not be the problem I at first feared.

 

Dave.

[Crosland]

As to the shorting by buffers that will ostensibly shut the command station down rather than fry the decoder as Andrew has said, point taken but I think it still applies that putting even momentary very high currents through a decoder is not a good idea.

<sigh>There is no current through the decoder, that's the whole point.

 

Andrew Crosland