Oh for a simple but effective pick-up system

[Dave K]

I am trying to complete a Perseverance chassis kit for an old Airfix 14xx.

The instruction suggest using phosphor bronze strip bent in a "U" shape attached to single sided copper clad glued to the top of the chassis side. The kit even included some phosphor bronze strip and single sided copper clad for the purpose. This seemed the ideal solution as the underneath of the body rests on the top of the chassis.

After attaching the copper clad to the chassis and bending the phosphor bronze strips and checking were not shorting out on the chassis a test run found them to stiff on the back of the wheels and broke off after it tried to adjust them.

So far the only part of this experience that has worked well is sticking the copper clad as at least I have a decent anchorage point for the wire to the motor/DCC decoder.

Can anyone out there help

[John Bateson]

May not be too helpful but MRJ 187 p315 has a diagram of a variation of the PB strip option
John

[grovenor-2685]

Dave,
Any chance of a photo of your problem? Might make it easier to see possible solutions.
Did the PB strip actually break? The material needs to be springy but should not be brittle, perhaps you need some new strip (or wire).
Regards

[Tim V]

From the description, I would suggest the copper clad was too small a piece, and the PB strips were too short.

[David Knight]

Dave,
Have you had a look at this? <http://www.clag.org.uk/tedpick01.html> Variations on this theme have worked for me.

HTH

David Knight

[Dave K]

Dave,
Any chance of a photo of your problem? Might make it easier to see possible solutions.
Did the PB strip actually break? The material needs to be springy but should not be brittle, perhaps you need some new strip (or wire).
Regards

Keith,

Attached are a couple photos of the chassis as requested.

Photo of modles 005.JPG

Photo of modles 007.JPG

I hope this makes the problem clearer but the PB strip is breaking on the outside of the chassis where it is being adjusted as it is applying to much pressure on the wheels. Sorry it has taken so long to reply but I have been playing with the max forum file size,

[Tim V]

You're using right angle bends instead of round bends, it's bound to fracture across the strip. The concept also creates wipers that are too short. They need to be longer, otherwise they won't "follow" the wheels as they move sideways. This design will also create a lot of friction, which will affect the smooth running.

if you want to stick with this design, try using narrower strip with a continuous round bend at the top over the frames. That way the spring will be over a longer length.

[Terry Bendall]

Dave

Rather than phosphor bronze strip, why not try PB wire - I use 28swg from Eileen's on the diesels and this always seems to work. Howevere the comment about making the pickups as long as possible is very true.

Of course you could always use split axles....!

Terry Bendall

[Dave K]

if you want to stick with this design, try using narrower strip with a continuous round bend at the top over the frames. That way the spring will be over a longer length.

Tim,
1. I wish this was in the instructions. But
2. As the footplate sits on the frames, in fact I had to modify the frames as the loco would have run too high, I think the weight of the body would have squashed the 'U' flat and press to push on the back's of the wheels.

However

Of course you could always use split axles....

I wondered when the spilt axle would raise its head.

Rather than phosphor bronze strip, why not try PB wire - I use 28swg from Eileen's on the diesels and this always seems to work. However the comment about making the pick-ups as long as possible is very true.

Terry,
After my Saturday's 'Southwark Bridge' work out and a look how some of there locos pick-ups I've come up with this.

Photos of models 007.JPG

I've use 33swg PB wire as this is the thinnest I have and the loco has moved backwards and forwards successfully on my 18" test track. Now to get it run with the rods on Terry

[Tim V]

Looks a bit more workmanlike, you may need some insulation if the pickups get dragged against the frames.

Next time have a go at split axles

IMG_2227.JPG

[Elventhumbs]

Dave

I built a Perseverance Metro Chassis which was very much my "Mark I" P4 project. I used phosphor bronze wire wiping the top of the wheels rather than under the chassis. That seems to work. It even worked on Iain Rice's clay dries layout which has some deliberateiy uneven track on it. The Great Man allowed me to run it when I went to the training session he and Mike Sharman ran last year (was it?) and I expressed some disbelief that the model would run at all.

Not sure that I can organise photos of it on to the Forum, though, if this would be of interest.

[Jim Summers]

Not necessarily the best way to do it (but it was an afterthought, and it was me) is seen in my article on bodging a J88 in the current Scalefour News. The photo is fairly clear. I filed away part of the frame to give a recess for the p.b. wipers, and slipped some sheathing from electrical wire over them to ensure they didn't touch the frames. They were attached to a pcb spacer at the top of the frames.

The pick-up wire is 30 swg.

You can use a thicker gauge and hammer it flat at the extremities. That bit isn't my idea but I've seen it work.

Jim

[45609]

Hi Dave,

Having tried a few different types of pickup and the only ones I have been happy with are made from coiled 33swg PB wire. Mine are basically the same as you have shown above. The pictures below show them fitted to my Super D 0-8-0. The pickup assembly can be removed completely if required by undoing 2 screws and desoldering two wires. In fact, now, all of my loco chassis can be stripped down to the frames if necessary. The pickup assembly consists of pieces of gapped copper clad, screwed to the frame spacers. Busbars are then shaped. In the case of the Super D these were rather curly so that they were not visible when the loco is viewed in profile. Once soldered to each side of the copper clad the coil pickups are attached. One thing to note is that I made the pickups on each side for the two wheels shown from one continuous piece of wire. It is easier to solder one pickup on rather than 2 consecutively and risk the first one coming adrift.

Cheers....Morgan

[Dave K]

Morgan,

I like your pick-ups, definitely a more refined version of mine. I also like the idea of screwing the PCB directly to the chassis so it can be removed for painting. Will have to bear that in mind for the next chassis, a High Level 57xx replacement, although the instruction make prevision for Gibson sprung plunger type pick ups.

[Dave K]

Tim,

Would like to try spilt axles again but need to be more skilled with a lathe. However as next on the building board is a High Level 57xx replacement with its dummy inside frame valve gear I think it will either be the Gibson plunger type of a more refined version of the current 33 swg wire and PCB.

[Tim V]

Gibson plunger - I would recommend you don't even go there Stick with what you've done already, plungers are non adjustable, seize, create a lot of friction.

[Rod Cameron]

Gibson plunger - I would recommend you don't even go there Stick with what you've done already, plungers are non adjustable, seize, create a lot of friction.

I've never really understood the philosophy behind plunger pickups in 4mm - you go to all the trouble of building a free-moving chassis, and then you fit brakes that are permanently on!

[Tim V]

The original MRSG/Studiolith concept (Prototype 18) of carbon plungers would probably have worked, the pale imitations that have followed have consigned plunger pickups to the scrap box.

[Elventhumbs]

I've never really understood the philosophy behind plunger pickups in 4mm - you go to all the trouble of building a free-moving chassis, and then you fit brakes that are permanently on!

But isn't that the problem with any pickup system which relies on one thing keeping contact with something else which is moving? The question seems to be one of how much friction becomes too much.

Tim's comment about the Studiolith version of the plunger pickup is in the fine tradition of the Society. We have to make do with what's available now and what we have in our (no doubt vast) stores of bits and unbuilt kits.

r

[jls_s4]

I recently employed Gibson plunger pickups on the front two drivers of an 0-6-0. Unfortunately the motor prevented fitting them on the rear drivers so I had to use PB strip bearing on the top of the treads. The arrangement seems ok. Years ago I used some plunger pickups on a 4-4-0; they work well but I can't remember the origin.

The problem with pickups is that you need maximum pressure to ensure good contact but minimum drag to assist free-running. Point or edge contact will generally achieve this but for long term running may wear quite fast. Flat contact is probably the worst as the area of contact is relatively large creating drag so the pressure has to be low impeding good electrical contact - they are also susceptable to dust or dirt lodging between pickup and wheel.

[Allan Goodwillie]

After some experiments back in the eighties in the Museum at Melrose where Scalefour trains were running sometimes 7 hours per day, 7 days per week and wearing out pick-ups at a fair rate (motors and gears and wheels for that matter) I went over to using fairly stiff N/S wire or phosphor bronze (30-33) with quite heavy pads of N/S strip on the ends carefully shaped and fitted to the inside of the flange with as long a lead as possible, fitted to copper clad sheet which also supported the brake rigging and could be detached in a oner from the chassis.

I found that the contact kept the flanges clean and you did not pick up the road dirt in the same way as you do with pick-ups on the top of the wheel which require the body off for proper cleaning, although they can be quite effective for picking up although there is a tendency for them to slip off the wheel on tight corners.

The N/S stays clean especially against the steel wheels and required less cleaning, the steel wheels took on a polish after a while and did not seem to require cleaning either. The result was much more effective pick up and longer periods between changing the N/S ends to the pick-ups, nowadays I am going over to gold strip, which is available for the pick up ends I will add a photograph later to show the arrangement. I too tried sprung pick-ups but did not like them for the reasons already stated. Tender pick ups are more problematic in some ways.

Allan