csb power

[Andy W]

I've been building a Brassmaster 0F which has been fun.


Being an MR modeller I'm not used to outside valve gear, so I had to do a lot of gapping with the sub sections - like the cylinder unit etc.



It's built with 3 point suspension as getting the csb pivot points in the right places proved difficult. It runs well - but it got me wondering if there might be a simpler way to pick up the power through csbs and avoid so much gapping. So I started playing with the tender chassis of a Gibson M class. I fitted some KM plastic hornblocks.



I drilled the pivot points using a HL jig and used cut down knobs on pieces of paxolin to keep the frames neutral.



I made up the chassis using ungapped spacers; shorted the wheels; and connected a pivot point on each side to a mini plug.



A bulb was connected to the plug and, even with an uninsulated footplate it lights up.



I'm not sure what this proves - other than that I should get a life!
However it does allow standard spacers to be used and wire can be soldered across the frames for brake hangers etc.
The question I now have is should I bother with any type of pick ups on the M loco itself?
Also if this were a tank loco could plastic hornblocks be trusted to wear? I have some Exactoscale ones so I might try them.

[grovenor-2685]

From an engineering viewpoint I would not really be happy using the springs to conduct the current, getting hot is bad for them. I would prefer to incude a flexible wire soldered to the axleboxes, which is what I have seen done in the past (at SLAG) with KM plastic hornblocks and split axles.
Mind you this is just theory and observation, my own experience is limited to wiper pickups so far.
Keith.

[Andy W]

Yes that's my worry as well Keith. However, using a flexible wire would still mean the csbs are carrying a current - so the heating problem could still be there. It's an experiment - so hopefully we shall see.

[nigelcliffe]

Pragmatic response to theory.....

(a) what is the current being handled, and is this likely to over-heat the CSB wire ? I suspect the biggest risk would come from running on a DCC layout with a huge power supply and shorting the loco via the pickups. The current draw to a Mashima motor shouldn't be an issue.

(b) how hard is it to slide out the CSB wire and replace it should it be damaged from over-heating ? In many cases, removing the wire is fairly easy.


So, that reduces the problem to "are the plastic guides any good ?"

An alternative, at least for tenders, to the plastic guides would be to use thin double-sided PCB as an overlay over the metal frames, and then fit metal hornguides to the PCB. Eileen's sell thin double-sided PCB. Pickup wires could then be fitted to the PCB or metal hornguides.



Though I have built split-frame locos, its the conventional way in 2mm Finescale, I tend towards the "which is simplest" approach. So, if wiper pickups and insulated driving wheels is the simplest, I would use that. If split-frame is the simplest, then that's the choice. In the most general of terms, locos without valve gear favours split frames, valve gear usually points to wiper pickups.


- nigel

[Will L]

Pragmatic response to theory.....

If there were a like button, I'd have clicked on it.

[John McAleely]

If there were a like button, I'd have clicked on it.

Bookmark that thought for a couple of months....

[Guy Rixon]

I would have thought that a CSB wire would always be a bit thicker than a spring pick-up wire, so the current through the body of the wire wouldn't a problem. If there was a problem with current, I'd expect it to show up at the contacts between the beam and the bearing carrier and between the beam and its supports. I can't see from the photo how the axle bearings are connected to the CSBs: are those Hight Level etches? If so, the contact area is probably quite small. However, a knife-edge contact under slight, mechanical load should make sure that there is always an electrical path.

[Andy W]

Yes Guy the carriers are HL etches. As I said this is a whimsical experiment I tried out of interest. I suppose I have to get on with building the rest of the loco now to see if it works .

[BRUNEL]

Andy,

This system sounds good to me. No wonder the 'experts' are bookmarking it! I've been thinking along similar lines but using H L hornguides with 5 thou Evergreen sheet stuck to the outer face and the whole unit then stuck to the inner face of the sideframe. I'd use Hypo Cement for this from Andrew Hartshorn which seems good for sticking brass to plastic. Its main drawback is in getting the wire back into the tube after using the stuff! Myopia would be a distinct advantage here!

As for the fulcrum points, I'd thought about a small piece of suitably sized cable insulation fitted to an oversize hole in the chassis into which the handrail knob was fixed with adhesive. But I like your idea of using paxolin. Are you using double-sided material soldered to the chassis and, if so, how do you ensure electrical discontinuity at that point? Also, what thickness of paxolin are you using?

This whole concept, using an essentially unaltered chassis together with live wheels, split axles, and CSBs, must surely make for an unbeatable combination.

Brunel.

[Andy W]

Brunel,
the paxolin is 1.6 mm double sided. I drilled the pivot points in the frames using the HL jig, then I cut a strip if paxolin about 2 mm wide, drilled holes in it and cut the cubes. I then located the cubes by inserting a blackened shoulderless pin through the paxolin into the frames. I soldered these blocks in place then pulled the locating pin out. I tinned the top face of the paxolin and cut the shoulderless knobs for the pivots short so their "tails" wouldn't touch the frame material. I lined them up using a length of wire and just touched the tinned surface to make a joint.

I think for a loco, however, I might pinch Nigel's idea of using very thin paxolin as sold by Eileen's.

I've used this before on another tender experiment:

viewtopic.php?f=19&t=2729&p=24429&hilit=tender+split+frame#p24429

so I've some in stock. It's useful stuff.

Andy

[DougN]

My suggestion is to go and find the 1mm double sided PCB that is available. A friend picked some up at Scalefourum 2013 for me from Ambis.... funny thing is it took me until after the 2014 Scalefourum (that I made it too!) to use it for the first time.

Setting up the chassis with glue, plastic Etc sounds like the Chassis2 jig would come in very handy.

I have been building another chassis and I can see the little challanges are disappearing fast but with the jig it does take some time to see the way through of using the jig with the instructions as some things need to be done in different orders!

[BRUNEL]

Andy,

Nigel's suggestion that o.3mm copper-clad be fixed to the inside face of the side frame sounds good at first sight, but my instincts tell me that your original concept, using thicker material, was better because it provides greater purchase for the handrail knob. That way, the advantages of using the original frame spacers are preserved. Might I also suggest that the hole in the copper-clad face in contact with the chassis is countersunk slightly, so that the risk of electrical continuity is reduced in the event of the knob being a fraction over length?

Brunel.

[nigelcliffe]

Further explanation of my idea (and its all theory..... I may try it one day.).

For the hornguides, 0.3mm or 0.3mm double sided PCB, because the thinner the better in this area, minimum change of the hornguides from the line of the frames.

For the CSB pivot points, either as suggested use thicker material, OR, thin material will require some work to ensure electrical isolation and accurate positioning of the handrail knobs. I can think of ways of doing it with thin material, but thick PCB on for the handrail knob pivots sounds so much simpler.



- Nigel