D869

A interesting topic. The question of custom diesel and electric loco/MU chassis is one that I have pondered on several occasions. Usually for things where an RTR chassis with the right dimensions is not available. I completely agree with most of what's been said but I still feel uneasy about the idea of binning (or most likely stashing in a drawer) most of a quite new RTR model... even if the result is easier/better/cheaper etc. Maybe it's just a hangup that I have. The answer is often 'sell the rest of it on eBay'... I just dont seem to ever get around to doing that. Personally I'd prefer an option for arriving at a diesel/electric loco or MU chassis where I can have some design input and choose things like whether to mount the motor low or high, flywheels and so on. The sticking points for me have been (as Chris said) the cost of buying so many gears and also figuring out how to arrange things like prop shaft bearings and bogie pivots to hold all of those drive train bits in the correct place in three dimensions. Cannibalising old locos for gears does seem like a solution to keep the cost of the drive train down. If I'm designing a custom chassis then desigining it around the available gears in my own junk box is not a big issue. Transferring the drive to the axles may be more of a problem unless the gears happen to be from a Farish loco. I've done my share of 3d printing (or rather Shapeways etc. have done it for me) but it seems to me that designing something as complex as a diesel chassis seems likely to require multiple iterations of test prints. Sorry, not a lot of positive ideas here... I would like to have some... I just don't have many on this topic

Isn't it obvious? The beer mat is under your pint.

Thanks Nigel. I have another DMU on my 'to do' list and have been wondering what to do for a chassis without paying through the nose to cannibalise an RTR model. My first ever DMU kit used a heavily butchered Lifelike GP40 chassis as per the instructions but the 2 axle drive never really worked very well and in my ignorance I had chosen a Calder Valley DMU anyway. I still have the bits somewhere. The second used a Kato chassis from MG Sharps. The wheels are modified (de-insulated) 1980s vintage 2mm Association coach wheels. It runs really well but the bogie wheelbase is quite wrong. Green Max chassis were recommended for a while but these seem to have been unavailable for ages. A pity because they did a 17mm wheelbase bogie. Unfortunately 17mm seems not to be an option for the Tomytec bogies but I might have to live with that - I dont intend this project to turn into an epic.

Hi Simon, I dont want to be discouraging but I'd want a loco to be running a lot more slowly than yours is doing in the videos... then you'd stand a better chance of observing what might be going wrong. I'm not sure if your loco seems too rapid because of pickup issues or stickiness in the mechanism or perhaps your motor and controller don't like each other. Pickup issues could be temporarily overcome on your short test track by using some flexible leads from off track or a temporary pickup 'tender' with flying leads... I used a bogie from an RTR diesel myself. IIRC you are using the Association 'can' motor. I tried one of these a few years back and could never get it to run well - maybe it didn't like my controller or maybe it was just a bad motor. I switched to a Nigel Lawton 8mm coreless motor and suddenly things became a lot better. I know others have had success with the 'can' though so it can be done. Regards, Andy

A Sundeala pointwork building board and drawing pins for me.

Definitely turn the job over and peel the paper off. Some paper stayed put on mine when using Pritt. I gave it a quick rub with some wet & dry to get rid of any bits that had real thickness and then carried on.

A washer restricting the end float will also become a bearing taking the end thrust, at least in one direction... so only do this if you can arrange something that will do a better job than the ones in the motor. Run in both directions by all means but do keep checking the motor for heat, especially when it is working against a known tight spot. regards, Andy

As Jim says, a spell of running in is always worthwhile before expending further effort. If that doesnt solve it then take your time and take a close look at where it happens as the mechanism moves. I looked at your video and couldnt really be sure but you can test some more. If it is always at the same crank angle then it's almost certainly something related to the wheels, cranks etc. If it is not matched to the wheel position then it is more likely elswhere in the drive train (e.g. idler catching on something). Binding with one side at TDC suggests the rods on the opposite side are binding (the cranks on the other side will be at 3 o'clock or 9 o'clock putting the coupling rods in line with the axles). Maybe too long or too short between one pair of wheels, or a bent crankpin perhaps. If you suspect a rod length issue then experiment with swapping sides (with the oil pots pointing downwards) and fitting the rods to just one pair of wheels (turn them back to front to do this). This may help you to isolate the issue although if it is only in one direction then it could be quite elusive. Binding with the cranks always at or near 45 degrees suggests a quartering issue. Good luck!

I'm a big fan of 'unpainting' for tidying up tricky boundaries between colours. If the first colour painted is properly hardened (several days ideally) then any stray bits of the second colour can be dealt with after they have dried for an hour or two using the end of a cocktail stick dampened with thinners. Sometimes I have used a thinners dampened brush to gently shepherd an edge back to where I want it. Timing is key - too soon and the thinners will spread the paint and make a mess. Ideally it should just soften the paint enough to move or remove it.

Well, I do blame him for much of this... him and the late Pete Wright's book anyway. No working inside motion though so I am still somewhat low down on the insanity scale compared to others who have gone before. Thanks Simon.

Did it? Can't say that I noticed. Takes me flippin ages to finish a coach. Maybe you just took it a bit easy to give the rest of us a chance Nice work Jim. Regards, Andy

Thank you Andy. It has its faults but I'm pleased with it so far... just hoping I can finish it without mucking it up really Hope you are keeping well and keep up the good work with Blueball Summit.

Injectors... My first thought was that these were mounted behind the cab footsteps so a couple of pipes coming out from behind the footsteps would suffice. Looking at photos more closely though told me that I really could see the inector. Pasting a link seems to put the picture in line... hope that is allowed... Looking at more photos just made me quite confused until I looked even more and figured out what I think was the story... Early photos show a horizontal injector type thing mounted under the cab floor ahead of the footsteps. All LSWR and SR era photos on the mainland that I've seen show this arrangement. BR era photos show a different arrangement as on the pic of 30225. It took me a while to find a photo showing a rear 3/4 view but eventually I did. No visible pipework behind the steps. Isle of Wight locos seem to have acquired a different arrangement completely so all of the time spent puzzling over photos of Calbourne was in vain. As far as I can see the IoW do hide the injectors behind the steps and have some interesting loopy pipework. After trying to get a clearer picture of the injector on an O2 I tried randomly searching for pictures of injectors by different manufacturers. Searching for 'gresham and craven injector' turned this up... ... which seems pretty much like the ones visible in the O2 photos. Pete Wright's book didn't have a way to make this type so I had to make it up as I went along... 0.8mm rod, a flat filed on one side, centre punched and drilled 0.4mm. Several attempts may have been needed to get the holes reasonably close to the middle. It's nice that the camera focused on the cutting mat. The 'pipes' were rod that turned out to be 0.45mm so I turned a very shallow taper on the ends which is handy because then they stay put in the holes while the solder is liquid. One pipe notched and a short length of the smaller rod notched to fit across it Soldered up, a twist of 5 thou fuse wire on each pipe and a crankpin washer on the upper one. The O2 photos dont show a big flange on the other pipe. 2 injectors all ready to go on the loco. Injector on the loco. I think you can just about see it. Nice bit of Blu Tack residue on the tank too. Usual words about cruel enlargement blah blah...

A further update on the O2 build... Before I could fit the cab roof I needed to sort out the fitting of various pipes that pass through the cab front. The first job was to fit the handrail knobs (or 7 out of the eventual 10 anyway) and the extra firebox top valve and pipe that some O2s had so that I could mark the locations for the holes in the cab. I even used some low melt... on the left hand handrail knob on the smokebox. ... and then took the cab front off so that it could be drilled. Not good for the feeling of progress... Once the cab back together the various twiddly bits in this area could be assembled... Does anybody know what the extra valve and pipe next to the safety valves was for? Some O2s have them and some don't. Getting the cab roof lined up took some care and a peculiar clamping arrangement to let me adjust it and then solder it... When it came to the roof ribs I reviewed the various suggestions kindly made by folks earlier in this thread and decided that Jim's way was the most difficult option so I chose that. 20 thou was about the thinnest strip of 5 thou brass that I could reliably cut. For the transverse ribs the strips were curved by pulling them between two pairs of pliers over a 3/4 inch bar. It took several round of this to get enough curvature and the strip tended to refuse to stay upright while being curved but eventually I got it done. The first rib was put on without any special clamping arrangements but then I thought of this setup which allowed me to keep the rib in tension while soldering it. Not sure how well it shows up - basically the strip is left long and one end held in the vice. I think it made the job a little easier but it was never going to be easy. On the plus side, I did find that my 25W iron had just enough heat to do the job... which gave me a lot more control than resorting to the big 80W iron. Then it was more filing and scraping to clean up the stray solder. Once the ribs were on, I cut some 15 thou scrap brass to fit between them and then filed all of the ribs down level with this. 15 thou (plus 10 for the roof itself) is probably a good deal over scale but at least they still look like proper ribs - I was worried that if I filed them down much further they would lose that look. For the final pic today I thought I'd have a break from photos of the O2 under my bench lamp and take it out for some natural light. The BBQ shelf was a handy spot. We've had '2mm in the Garden' on this forum before, so should I rename my thread '2mm on the BBQ' ?

Looking great Izzy. You are really making some rapid progress there. We've used cyano to good effect where the corners of card buildings get frayed - just a minimal amount applied with a pin and allowed to soak in. Once dry the fraying can be trimmed, filed or sanded and the paintwork touched in. Regards, Andy

Thanks Jim. I keep considering switching to low melt but there is always something else to go on afterwards so (so far) I keep deciding to stay with my usual electrical solder. To be honest the smokebox door was the only thing that really risked unsticking anything else and that went OK. The big Antex worked quite well - it flows the solder pretty quickly and without fuss and it sets solid pretty quicky because the mass of brass sucks the heat away.

Looks good with the end mill. Reminds me of 'The Mole' in Thunderbirds. Paint it all grotty black and you could be branching out into Steampunk/Sci Fi.

I finally bit the bullet and soldered the big lumps onto the boiler. I tried Pete Wright's recommendation of using a little blowtorch but didn't get on with this approach - it just got things too hot, too quickly and I was concerned that it was going to unsolder things. I resorted to the big Antex iron and put up with the stray lumps of solder, cleaning these off afterwards. I also did the smokebox door hinge. I don't have any suitably sized strip so filed down the end of some MSE 18 thou square rod until it was about 8 thou thick. Pete W recommends adding the hinge straps as a pair so that they are in line and parallel before starting. Again the big iron was deployed with a good deal of scraping and fibreglass brushing afterwards. The hinge pin is 0.3mm Albion Alloys brass rod with two tiny bushes of 0.3 x 0.5mm tube at the top and bottom.

The association shop does 3d printed motor mounts. I haven't tried them myself. Others use those double sided sticky pads or just a big blob of glue. Some use stiff feed wires to the motor terminals. I use Blu Tack which sounds like a bit of a bodge but actually works very well, at least on coreless motors which don't get warm.

A thought... could you make a diffuser by printing a suitably blurred blob onto thin paper? - darker in the middle and lightening towards the outer edges. No idea if it will work but might be worth a try.

Hi Izzy, Lovely job on the signals. I've done a couple of route indicators for St Ruth, one being an electrical one of the WR variety. Even illumination is a challenge, as is preventing light leakage. Mine has 4 lights... plus the semaphore has working signal lamps so keeping the number of wires to a minimum required a good deal of electronic gear below stairs. I dug up the links to the relevant posts in case you want a look... https://www.rmweb.co.uk/community/index.php?/topic/65499-whats-on-your-2mm-work-bench/&do=findComment&comment=2402268 https://www.rmweb.co.uk/community/index.php?/topic/65499-whats-on-your-2mm-work-bench/page/54/&tab=comments#comment-2406140 https://www.rmweb.co.uk/community/index.php?/blogs/entry/18271-branch-home/ Regards, Andy

Lovely job. Always nice to see something cut out of raw brass. They kinda look more impressive unpainted to folks who know how much effort goes in... but all of us put paint on sooner or later. The only other model I've seen was built by Jim Allwood. I don't know the full story but I think his was made from a heavily modified kit, one of the modifications being to motorise it. There is a pic of Jim's at http://www.2mm.org.uk/layouts/weltondown/index.html

Glad it's not just me. I saw him at the Midlands Model Engineering show last October but I think he just had big stuff on his stand. Regards, Andy

Thanks Ian. I think in my case the main problem was with the drill and to some extent my way of driving it. The tube for the boiler was marked out on the lathe and I made an attachment for the toolpost which can take either a centre punch or the shaft for a small drill chuck (cannibalised from an old, broken flexi drive). The punch was turned on the lathe and hardened and that worked very well. The drill not so much for various reasons. I might have been better off just marking out on the lathe and then drilling later on. I think that the drill bits themselves are also partly to blame - some drills cut really well from new and others hardly at all. I think that getting decent tiny drills is a pretty hit and miss thing. I was using the Titex drills that I bought in 10 packs at Warley a few years back. I have some 0.31mm drills that are absolutely brilliant but the 0.46mm pack seems basically... not great. I wish I'd bought more of the 0.31mm variety but at the time I had no idea if they were good or bad... and it seems the answer was 50:50 between the two packs. These drills do still break. I'm now down to 6 surviving 0.31mm drills so I'm quite cautious about how I use them.

The curvy valve cover seemed to go OK - the milled steps gave enough 'purchase' to help me keep a round escapement file straight enough to file the concave curve. The convex curve was done with a whole bunch of different files - flat, half round - whatever would reach the right part of the curve. Having this attached proved that I hadn't got room to tilt the boiler enough to clear the (as yet non existent) front lamp brackets. I've re-done the rear supports for the boiler to resolve this. They are now right at the back so the boiler can be tilted more steeply and sooner when it is removed. I've made the handrail knobs (plus spares) but havent done any more on the handrails - it's quite a puzzle to figure out the best order to assemble things. I think I will need to drill a bunch of holes in the cab front to provide support to the back ends of the handrails and boiler top pipework... once I can mark exactly where they need to go. I've been using the watchmaker's lathe to make the remaining twiddly bits to go on the boiler. Once these have all been test assembled, I think it will be time to do a final rub down of the boiler and then attach the boiler fittings, starting with the bigger lumps of metal. The whistle (0.8mm dia) and the manifoldy thing that it sits on... this is a bit of a guess because I don't have great photos showing how this all goes together and the setup seems to vary between locos and over time... Clack valves... I hope. From 1mm brass. Drilled 0.4mm for the spigot into the boiler and axially for the feed pipe... Trial fitting of the whistle, the other boiler top valve (whatever it was for??) with the other big bits plonked into place... You may have noticed that the handrail holes looked quite big in earlier photos. Thats because they were. I wasn't convinced the 0.3mm drill would cope with the K&S brass tube so I used 0.46mm... which didn't cope that well either. The holes are way too big for the split pin handrail knobs so I've soldered bits of 0.3 x 0.5mm Albion Alloys tube into each hole. We'll see if I can add the handrails without dislodging them too much.