7mm Mickoo's Workbench - JM LMS Garratt - MR Compound

Discussion in 'Area 51' started by mickoo, 8 September 2018.

  1. cmax

    cmax Western Thunderer

    Another cracker on the way
    mickoo likes this.
  2. mickoo

    mickoo Western Thunderer

    Still plodding along with the King Arthur, getting there though.

    One point to watch for are the cast slide bars and crosshead, lovely castings but the slide face distances are not the same. The cross head is 4.6 mm the gap between the bars in 5.2. The motion bracket does pinch the rear end to the correct gap but you end up with a taper, it's hard to see until you look at the crosshead flanges when fully forward and see their nearly falling out of the slide bars.

    There's two options, bend the bars closer at the front, but then you end up with a bit of a dog leg between the end of the running faces and the piston face. The second option is to open the motion bracket out so you have 5.2 mm all along, then shim each slide bar face with 0.2 nickel silver. I chose the latter and it does give a nice step at the front that the cast ones had but was a bit small. Quite a bit of work but visually a lot better.

    The only other niggle is the slot and tab construction, 99.9% of the time it's perfect, fully recommended and something I do on my etches. Most of the time the tabs once trimmed flush are covered with something else or on part of the model not easily seen.

    The Urie cab ignores all that, not once, but eight times, leaving tabs to trim back and make flush on the most visible part of the model, the roof exterior. They look smooth, they feel smooth but a pro paint job is very thin and it'll show a witness mark instantly. The only solution is to try and fill with filler or spray a thicker layer and cut back, it's a lot of work but necessary.

    I get why the tabs are there, they are a massive boost when you fit the roof and ribs but the clean up afterward is a chore.

    Other than that, the rest was a join the dot to dot puzzle, the front end and smoke box with saddle just all slotted in place, half a dozen solder dabs and dropped into place. I think it's about 1-2 mm too low but once the footplate is on it'll be easier to judge and pack out the fixings as required.





  3. Tim Watson

    Tim Watson Western Thunderer

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  4. mickoo

    mickoo Western Thunderer

    MOK King Arthur DCC install update.

    Rather that faffing around pushing everything in from the firebox interior as is custom, I've opted to make a bespoke tray and sled to hold all the DCC parts and speakers. It's a bit of a tight squeeze but it does all now go in the front end much easier.

    It would of been much easier if we'd opted for the V4 chip, but the spec for the big Faulhaber motor, long trains and gradients means that the much higher (considerably bigger physically too) power rated V5 chip is a must.

    The upturned base speaker will fire down though the oval hole in the tray and out under the middle of the engine, a smaller higher frequency speaker (shown in the photo as sugar cube speakers but might go up a size or two now that we have more space) will be fitted to the front of the sled ahead of the DCC chip and under the chimney.

    A new smokebox door fixing plate was worked up and the door casting modified to take a central fixing, to which the dart casting will be affixed later.

    The kit does not provide a smooth smokebox wrapper without snifting valves or smooth face plate for early engines, so it's a case of getting the crayons and sharp stick out and making your own I'm afraid.






  5. BR Tony

    BR Tony Member


    This is brilliant as fitting DCC sound into highly detailed prototypes is always a challenge. Adding this type of arrangement to other builds would be very helpful towards dealing with this. I really like your solution - another arrow to your bow going forward? Did the chip come loaded with the necessary sound files?

    mickoo likes this.
  6. simond

    simond Western Thunderer

    Second that; a “sled” for the DCC is a solid bit of engineering. Nice!
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  7. mickoo

    mickoo Western Thunderer

    Tony, Simon,

    Cheers, I cannot take all the credit, Richard Spoors and Peter (PAD) had the idea first, probably even others I'm unaware of, on Richards A2 I inserted an inner boiler tube to aid guiding and holding the speaker and chip into place. Fitting was via the firebox with the model upside down and all a bit of a faff. Richard and Peter had done it through the front with a bayonet type fitting smokebox door.

    Unfortunately the four lugs on the King Arthur door prevent it from being turned to secure it with a bayonet type fitting, so I had to come up with something else. Whilst doing that I decided to try and make all the DCC one sub assembly that fits onto a sled you can just slide in an out.

    You have loads more room if you do a Maunsell engine as the door and associated flange have a greater diameter, the Urie one by comparison makes tolerances very tight. The worst part is the shoulder of the DCC chip when mounted on the breakout board, at one end are a row of chips and they push the envelope in the top corners right out to the max opening you can get away with on the Urie door.

    The upshot was to lower the tray but then keeping it full width meant that the lower corner cut outs in the face plate would be seen outside the door. To resolve that the tray was narrowed and the sides angled, it means the tray is just a bit narrower than the DCC board but the stand off screws jack the board base up to allow it to pass through the max width opening available.

    I still need to add the wires to the relevant tabs but I think we have room to do that and make sure nothing shorts out, it's all very tight but this is the biggest chip and probably speaker you can get in a UK outline steam engine.

    What we have above is the MK II rendition, the Mk I had the speaker under the chimney but feed back suggested sound would not be that good, especially jacked up on the pegs to give clearance.


    On the Mk I you can see how close the chips are to the cant rail/shoulder cut outs in the front plate, the speaker had to be jacked up to overhang the tabs on the DCC break out board and reduce length.


    A couple of beers and some after shot doubles (a good German engineering friend I worked with on crane projects, told me all solutions lie in the bottom of a beer glass, the level of the problems difficulty was measured in the number of beers need to be drunk to find the solution), along with scribbling on a napkin resulted in Mk II with the speaker and chip flipped.

    It does mean that the sound is now going down and out of the middle of the loco; there is an opening in the boiler base etches, this is to enable the original kits planned drive to the middle axle. I was going to blank that in but leaving it open will drastically improve the sound quality, so that's a compromise I'm happy to accept.

    The chip has no program at all at the moment and I'm tempted to leave it to the DCC guy, but to save any potential cocks ups I might load a US diesel pack in to test motor control and make sure the speakers all work. That way the DCC guy just needs to drop it on the test track and reprogram, no need to take the model apart at all. We'll see how I feel toward the end about it all.

    If a model allows and the required chip and speaker fit then this'll be my preferred option for future DCC model installations, it's a lot of extra work, more than is readily apparent I suspect, but the benefits far outweigh the early pain.
  8. michl080

    michl080 Western Thunderer

    Brilliant idea!

    A "like" is not enough.

    Deano747 likes this.
  9. richard carr

    richard carr Western Thunderer


    I would definitely advise you to test this set up as those type of speaker cause a great deal of vibration and need to be held very firmly in place.
    I fear that although the speaker is firmly bolted to the brass base that brass base will rattle against the tray. I have had this issue in a number of diesels using this style of speaker, there is just so much bass !

  10. mickoo

    mickoo Western Thunderer


    I've been looking at that this afternoon, it needs resolving before I fit the boiler in place.

    I've opted for two pieces of angle, one on the tray and one on the sled, the one on the sled is angled slightly so that the further it is pushed in the tighter it wedges under the one on the tray.

    That holds the front and rear ends but I suspect I may have to add another at the front end of the speaker housing, that'll probably be a lug with notch in mounted vertically to the tray side and engaging on a short stub sticking out the side, I can go slightly wider with the spigot than the base higher up, maybe a fraction wider than the top of the angled raves.

    The mid and rear parts of the tray will be securely fixed to the boiler formers, so I'm not overly worried about that moving so much.



  11. Yorkshire Dave

    Yorkshire Dave Western Thunderer

    With the Faulhaber motor a HO scale decoder would have been sufficient.

    The ESU Loksound L is a bit overkill but naturally it's the client's choice.
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  12. Yorkshire Dave

    Yorkshire Dave Western Thunderer

    Another solution is to fix the speaker in with silicone sealant.
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  13. mickoo

    mickoo Western Thunderer

    Even with 10-14 coaches on a 15m 1:50 grade?

    My biggest concern is actually getting enough weight in there to get it to drag that lot.

    We also wanted dual speakers, a big base unit and a smaller unit, I think only the V5 has that option, put another way, the V4 I have here only has one speaker output. It does raise the question if you actually need two speakers, is there a real benefit for two speakers.

    Either way, with the sled you can always downgrade later if necessary, there's more than enough room, but if we had gone smaller then we might not have been able to go up in size.

    I could do that but how do you drag it in and out on the sled, I'm presuming you mean permanently fix it to the tray?
    Last edited: 16 September 2021
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  14. mickoo

    mickoo Western Thunderer

    Well the speaker works and it sounded okay to me, well no worse than anything else I've heard; but then my hearing isn't the best and it sounded the same as the big one securely fitted to the base of the Dash 8.

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  15. Big Train James

    Big Train James Western Thunderer

    It's not so much the difference between the V4 and the V5, but rather between the V5 and V5 L. I believe the V5 (essentially HO) only puts out 3 watts of sound, whereas the V5 L (what I think of as for O) can push 3 watts on two separate outputs, totalling 6 watts. That's my understanding, which could very well be wrong.
    BR Tony likes this.
  16. Yorkshire Dave

    Yorkshire Dave Western Thunderer

    The V4L I have has two speaker outputs. Two speakers - I suppose it depends on how realistic you want the sound to be.

    I used a V4L with two speakers in my Dash 8. The larger one with the better response in the low frequency range in the body and a smaller one in the tank which acts like a tweeter with the higher frequencies.
    Dash 8 40B 028.jpg

    Yes, fixed to the tray.

    Is the sled tight in it's carrier/holder within the boiler/smokebox without any movement? If there is the slightest movement it may be necessary to somehow wedge the sled tight in it's carrier/holder to prevent the resonance of the speaker exciting the sled and it then rattling against the sled carrier/holder at certain volumes and/or frequencies. Otherwise it may lead to unwanted buzzing/rattling noises.
    Last edited: 16 September 2021
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  17. Scale7JB

    Scale7JB Western Thunderer

    Would a self adhesive foam work to take out the vibrations? Maybe have a look at the Tesa website?

  18. mickoo

    mickoo Western Thunderer


    I have the same V4L in my Dash 8 that you set up for me :thumbs: It's not physically any smaller so wouldn't of helped in that respect, I suppose cost might be the only factor between the two and maybe power output.

    I cannot fix the speaker to the tray as it'll never come out again, once the boiler goes on the tray is inaccessible, so the speaker and DCC have to be fitted to the sled for repair/replacement.

    The tail end of the sled is now secured with the angled strips (see posts above), the front end with a 10BA screw, there may be some flex in the middle where the speaker front support rises up so I'm going to add a bayonet fixing there shortly. That will secure the sled to the tray and allow it all to be removable. The tray will then be soldered to the rest of the boiler rings as it's built up.

    I test ran the setup without the intermediate support and could not detect any buzzing or distortion, no more than the speaker set up on the Dash 8 which is mounted rock solid to the chassis, it'd probably be okay as it is but I'll add the intermediate support as belt and braces to be sure.
  19. LarryG

    LarryG Western Thunderer

    While one big base speaker or even two speakers will certainly give you some woof, this alone isn't enough IMO if the decoder set-up lacks realism or doesn't have sounds whose values can be changed. I tore my hair out drying to subdue sounds that were far too noisy in relation to other sounds.

    In trying to recreate the sounds we hear from the trackside, not the footplate, we are bombarded with clanking rods, the shovel hitting the hole, boiler hiss, the ATS horn and bell, even cooking egg & bacon on a shovel. Some can be reduced to zero but some can't. Most of my LMS and GWR locos sounded like they were ready for the knackers yard.

    Another problem equally important is movement control. In this respect, Zimo gave the smoothest take off from a standing start while one of my locos with an ESU decoder just set off at about 5mph missing out the gradual taking up of the train. I stuck with Zimo thereafter.
    Rob Pulham, richard carr and mickoo like this.
  20. Yorkshire Dave

    Yorkshire Dave Western Thunderer

    Hi Mick

    I was only thinking out loud as the last thing you want is the loco to be returned for minor adjustments and it's obviously easier make a sturdy fixing whilst the boiler is off the model.

    The diesel sounds (due their rumbling bass) at higher volumes with these speakers certainly cause the loco to vibrate and would appear to be a good test in a steam loco especially as the speaker is mounted on sheet metal. Out of curiosity did you test the other sounds on the decoder for any resonance such as the horn with its higher frequencies?

    You don't really want to name the loco 'Walls of Jericho'. :) and I'd leave the Dash 8 sound on the decoder for a laugh ;).