loco compensation/brakes/Romford wheels

[hayfield]

I bought a kit built loco from eBay, said there was a short and I saw it had an etched chassis and Romford wheels, so I knew my bid of £30 was safe and at worst I could use the components. Quite obviously it was a K's terrier, on inspection the chassis was built with beam compensation which had a lot of travel, there was a short, rather a lot of shorts, brake rodding was bent, as were some of the brake shoes and some of the wheel flanges could touch the brake rigging, after taking off the brake gear the compensation could move even further. On further inspection I think the motor is shot and the chassis is a Branchlines product. The rebuild will have the motor facing the other way away from the cab into the boiler/side tanks

 

 

As you can seethe middle and rear wheels are on the rails with the front wheel lifted by 3.25 mm, quite obvious too much. This raises a few questions

 

Firstly, how much movement is desirable ? then how do you limit it ?

 

Secondly,  can you have compensation and brass brake gear ?

 

Thirdly   with Romford and possibly Marlit wheels can you use these with both compensated chassis and brake gear?

 

As it happens with this Branchlines chassis I will dismantle it, then rebuild it to EM gauge, but if I rebuild it with compensation should I keep the brake gear and if so use 15 mm Romford wheels or buy Gibsons )

 

A forth element into the discussion is the use of plastic brake gear, has anyone used this method ?

[Bucoops]

Nick Easton's 7mm 04 has around 1.5mm deflection if I've assembled it correctly. I'd expect 4mm to be in the region of half that?

 

I've yet to build anything with plastic brake gear, but Alan Gibson kits come with it. I like the idea of it as it's the most obvious cause of shorts.

[Izzy]

All you really need is about 0.5mm max either side of the median. If a loco can’t work with that then there are some very serious issues with the track.....

 

I have never felt happy with centre beam compensation. Twin beam is more stable and although not ‘true’ 3-point compensation is more than enough normally. You can always allow the third (driven) axle to have a little downward movement to produce that if needed. 
 

Often used Gibson plastic brake shoes/hangers. Quite useful but if outside pull rods are involved then not so beneficial. The last fully etched chassis I built, an old Whitbourne models 43xx, had brake gear that pivoted out of the way to allow the wheels to be dropped out, which is handy, but not so easy/robust with plastic hangers. There should be enough room with metal ones really whatever the wheel/track standards.

 

I would guess the major issue with the above chassis is hanging the motor off the back,  (not a DS10 I think, too short, so possibly Tenshodo?), making the rear driver the main pivot point, so totally wrong weight distribution. TurnIng it around as you intend might make the rest quite okay.

 

Izzy

 

 

[MarkC]

I've built many chassis using Romfords and Mike Sharman's 'Flexichas' system, which has worked well for me.

 

Plastic brake gear? That helps, but I've also successfully used metal gear too. As above, you shouldn't need too much movement, 1mm is probably the absolute maximum required, so for normal viewing distances I find it easy enough to set up the brake gear with sufficient clearance to avoid shorts.

 

Mark

[CXW1]

I posted the picture below on my workbench thread a few days ago and I am assuming that it might be similar to your Terrier chassis. The chassis in the picture is scratchbuilt and for an EM gauge LNER J79 which has a wheelbase of 6ft & 5ft, so not far off a Terrier. 

 

The wheels in the picture are too big and are just some old Markits wheels that I am using to get the chassis set-up - by this I mean making sure that it runs freely without any binding and to get the beam at the correct height/angle. 

 

When the chassis is sat on the track or any other flat surface, the front two axles on the beam cannot independently move upwards like the front axle in your picture. The beam places some light downward pressure on both axles - just enough to keep them on them track. Both axles can independently rock on the beam. I've never measured how far the axles can rock but it won't be any more than 0.5mm in both directions. The beam on your chassis is possibly bent, broken or completely the wrong shape if the front axle can lift up while the other 2 axles remain on the track. 

 

The gearbox will be on the rear axle on the J79 and the motor will end up over the middle axle, so weight distribution should be fairly well balanced.

 

I have used this set-up on lots of 0-6-0 and 0-6-2 tank engines and it works OK. Izzy is correct in that twin beam compensation can be more stable, but I've always found single beams easy to deal with. 

 

You shouldn't have any problems using brass brake gear as long as there is a small gap between the brake shoe and the wheel. 

 

Hope this helps. Clearly there are many ways to achieve the same outcome and I'm not saying that my way is correct or the best way, but it does work reasonably well. 

 

Chris

[hayfield]

Chris

 

Thanks for the advice, looks like you are using High Level hornblocks, plus P4 with thinner flanges. I have some High Level hornblocks to try, I seem not to be getting on with Alan Gibson hornblocks, I have though successfully used Perseverance ones. I will have to look at the effect of using differing makes of wheelsets in relationship of increasing the diameter of the wheels

[CXW1]

3 minutes ago, hayfield said:

Chris

 

Thanks for the advice, looks like you are using High Level hornblocks, plus P4 with thinner flanges. I have some High Level hornblocks to try, I seem not to be getting on with Alan Gibson hornblocks, I have though successfully used Perseverance ones. I will have to look at the effect of using differing makes of wheelsets in relationship of increasing the diameter of the wheels

 

The wheels are the current Markits profile which they sell for OO and EM - nothing P4 about them. I have used High Level hornblocks for years and they work well if you can get the beam (or beams) sorted out. CSB is another option but I've never tried it. I've never got on well with Alan Gibson hornblocks for various reasons - I find that there is too much 'slop' in them and I kept burning my fingers trying to solder the nut on the top. 

[hayfield]

Chris

 

Certainly looks like the Newer Markit wheels have thinner flanges than its older Romford predecessor 

 

As said earlier I have bought some standard High Level hornblocks to try, I see he does a Mini & Space Saver. I need to order a gearbox so will ask if the smaller units would be better. They will certainly sort out the issues of guide wires sticking up too high. Thanks

[CXW1]

The current Markits wheels do have thinner flanges than old Romfords which makes using brass brake shoes less of an issue.

 

I've never had the need to use the space saver hornblocks. My understanding is that these tend be used where you have hornblocks on all axles (e.g. on an 0-6-0 with CSBs) and where there is limited clearance to fit a gearbox between two hornblocks. I have always found the standard High Level hornblocks to be perfect for use in a single beam chassis where the gearbox is on a rigid axle. 

 

Thanks

 

Chris

 

 

 

[hayfield]

Chris

 

Again thank you, I am being dragged into the 21st century as I have shied away from keeping up with modern techniques. I will have to sit down and read the instructions Chris sent me with them, plus I will have to watch Derek's (Eileens Emporium) video of setting up hornblocks on one of his jigs.  

[Captain Kernow]

I agree with what Izzy and John have posted.

 

I've built a fair few chassis with single beam compensation in both OO and P4 and this is my preferred method of compensation, in that it does the job (keeps the loco on the track and improves electrical pick up) and is simpler to build and install than twin beam compensation, individual springing and the (for me) dreaded CSBs (which I think are an over-hyped and unnecessarily complex 'solution' to a problem that was already solved with the earlier methods I mentioned).

 

You should have no problem at all with using brass brake gear and this will be much more robust than having to join plastic brake shoes to a brass chassis and brass or nickel silver brake rodding underneath.

 

After the initial adjustments, I've never had any problems with brass brake shoes causing shorts etc.

 

It is possible to build the brake gear so that you can remove it and in fact High Level incorporates this into the design of their chassis for RTR locos (I am just finishing work on a 74XX pannier with a High Level chassis and found the removable brake gear helpful when making adjustments to the chassis and also when painting and weathering).

 

Unless it is designed in as part of the chassis kit, however, my preference would be to build the brake gear integrally to the chassis. This is, of course, considerably easier if using Markits wheels, which you can remove individually.

 

One interesting issue I found when building the 74XX chassis in OO, was that the gearbox supplied was (at 11mm) too wide to fit between the standard hornblock bearings, also supplied in the kit.

 

If I had known this in advance, the hornblock bearings on the driven axle could have been thinned down in the vice or the slimline High Level ones ordered.

 

Unfortunately for me, I had already built the chassis and soldered the hornguides in position, so I had to resort to slimming the gearbox down (as per my recent blog post), which actually went surprisingly well (but only because there were already holes in the sides, that could take bolts and nuts to hold the thing rigidly in it's new, thinner configuration).