Class 22 Diesel (next project)

I have gone with a pair of mobility scooter batteries 12 volt - 22 amp hour in the little 0-4-0 shunter, the 4 motors are wired parallel as are the batteries giving 12 volt - 44 amp hours, its early days so will have to see how they cope over time. Cost wise they compared favourably with a 50 amp hour leisure battery which I was going to use, £65 for the leisure and £63 for the pair of scooter batteries.

I am thinking of going with the same for the large loco but 4 batteries, each pair wired series for 24 volt and then the two pairs in parallel to double the capacity though I may go up to 30 amp hour doubled to 60, the 4 motors will be wired parallel also.

I dont yet have any long term experience with the batteries but we have a club member who runs an electric with a pair of the mobility scooter batteries and he said the batteries are coming up 4 years old and still going strong. I have noticed though its quite light duty, he probably does no more than three or four 10 minute runs each track visit.

Not too good a photo of it but I sketched up the loco to get a feel for the size, twice as long (45 inches) as the 0-4-0 shunter. Looks as if it will lend itself to some good detail though over 20 fine grid vent panels may prove to be fun, it would be good if I can find some off the shelf material for those. Waiting the arrival of some metal and then I can make a start on the chassis.

Click picture to enlarge.

Edited By Ron Laden on 22/05/2019 13:57:09

Another sketch showing a design change to the bogie and motor mounts, I,m sure that the previous design for the bogies would have worked well enough but I wasnt happy with the shape and the way they looked. The bogie side plates were too deep top to bottom but that came about with mounting the motors to the plates.

The sketch below shows the plates more to the shape they should be though this wouldnt allow for fixing the motors to them, well not without some bracketry but I dont fancy that. So I have looked at axle mounting the motors, I did this on the 0-4-0 and it worked out well. The 0-4-0 has a single plate running on the axle with a motor mounted each side, I used tie bars and nylon guide rollers to retain (prevent rotation) of the plate whilst allowing the plate vertical movement with the sprung axle.

I dont have the space to do the same with the new shape bogie side plates so I have come up with the idea as seen in the sketch, with the limited space the problem was how to retain the motor plates whilst allowing for the vertical travel of the axle. The pair of plates would be sized and centered to leave a 3mm gap between them this would allow for a small amount of movement and retained to each other via a pair of strong compression springs, I have left off the top spring for clarity. The motors and motor plates will still protrude down past the bogie side plates but they will be inset by 25mm so shouldnt be too obvious. I think this should work but if I am missing the obvious please shout.

The usual way to prevent motor assemblies rotating around the wheel axles is by tie bars from the motor mount to the fixed bit of bogie. It is also better to have the pull point from the bogies to the main frame as low as possible to reduce weight transfer. Can you not have the motors higher, protruding from the top of the bogie frame, they would be inside the body

Hi Duncan, I,ve never been one for the usual I do like to look at new ideas, not that they all work out of course. I did use tie bars on the 0-4-0 and they were ok. I will give what you suggest some thought but I was just working on a fresh approach whilst trying to keep parts and assembly quite simple.

Ron

The 4 motors need a couple of mods, the first is soldering the brush wires. The wires are crimped in place under a tab and quite secure actually but I have gone belt and braces and soldered them just in case.

The motors will be sandwiched between a pair of mounting plates but there is only mounting holes (3 x M5) in the output shaft end casing. The rear end casing needs holes adding but the casing is cast aluminium and only 2.5mm thick, so I am going to drill and thread M5 and fix the screws in from the inside using retainer. There will be plenty of clearance between the screw heads and the armature and it will leave threaded studs on the outside for fixing to the plate using nuts, should be ok.

.

Morning guys,

I would appreciate peoples thoughts on the following:

On the bogie axle/drive assy I currently have the shoulder of an oilite bearing which at times can contact the revolving face of an aluminium drive pulley. The axle/wheel to which the pulley is fixed has 0,040" end float so contact wont be constant but there will be contact at times. The faces of the oilite and the pulley are very smooth and I am wondering if keeping them lubricated would work ok or is the aluminium eventually going to wear and pick up.

I have some thin 0.015" nylon washers, would it be a better option to fit one of those between the faces. I would prefer to keep things simple but I could bore the pulley and fit a shouldered bush either oilite or some other material so it is the two shoulders that make contact.

Thanks

Ron

Edited By Ron Laden on 11/06/2019 09:03:10

Edited By Ron Laden on 11/06/2019 09:03:32

My suggestion comes from Meccano lore, and may not be completely respectable!

By putting a loose washer or two between a wheel and frame, friction is said to be reduced because the wheel can slip on the washer and the washer can slip on the frame. Not sure of the logic but it seems to work.

I'd fit the Nylon washers; if nothing else they'd protect the expensive Oliite bearings from the Aluminium and stop the bearing grinding the Aluminium and making a lot of abrasive Oxide, which is not good if it gets inside a bearing. (Bit theoretical because even badly abused bearings might last donkey's years on a lightly used locomotive.)

Dave

Ron, I'd tend to use hard shim washers, similar to those found in electric motors, if I need them, and can't find what I want in the junk box I go to my bearing supplier who has all those sort of goodies. Some times there is a nylon/plastic washer between two steel washers.

Ian S C

Thanks Dave and Ian, I must admit I favour the idea of using a suitable washer/spacer and since my post I have found some PTFE ones which are 0.5mm thick 16mm ID - 28mm OD which is just about the exact size of the face of the olilite shoulder. I think with PTFE which is pretty tough and very low friction they should do the job well and keep things simple.

Ron

Hi Ron,

+1 on Ian SC's suggestion to use two hard shim washers for your application. Personally I would just use two greased steel ones. Reason for not using a plastic one in the stack is that anything soft in there will pick up dust and hold it, lapping away continuously at the harder parts. With occasional use as in your locomotive it may never be an issue but with prolonged use I've seen plastic bushings wear steel shafts 3 mm on dia and plastic washers wear solid steel bushings away by 6 mm. 10 cent plastic parts still looked great - multi hundred dollar steel parts were scrap!

Just food for thought. Good luck!

Edited By Jeff Dayman on 11/06/2019 16:57:06

Thats interesting Jeff but why two greased steel shim washers and not just one between the pulley and the oilite bearing..?

Ron

Hi Ron, Why two greased steel shims? just based on experience and some basic tribology theory.

If you had one shim between a rotating pulley hub and a stationary Oilite bushing, in theory if there is side pressure on the shim the shim will rub on the Oilite or the pulley or both, a high wear situation.

If there are two greased shims, in theory one shim may stall on the Oilite or rotate slowly, the other shim may stall on the pulley or rotate slowly, but the main relative rotation will occur between the two greased shims. The grease separates the shims and minimizes the wear and the shims being hard and relatively flat and smooth steel will have low friction coefficient to begin with. This usually will result in low or no wear on pulley or Oilite. It's not a tragedy if after many hours you have to replace the shims for 50 cents or a dollar. You have saved many tens of dollars replacing shims rather than a chewed up pulley and Oilite bush.

Again for occasional use the above theory may not matter much but just offering food for thought based on working on a LOT of machinery over the years, seeing what works best.

All ready to be shot down in flames now by the usual armchair experts!

Thanks Jeff, that makes sense.

Ron

Have you any shim stock from which you could punch / cut the washers?

And to use Graphite, or MoS2 grease rather than plain Calcium or Lithium grease, to minimise friction?

Howard

Ron

On the various grills have you considered getting them either laser cut or etched in either steel or nickel silver. They could be made from two laminated layers one with the grill vents the second and overlay to form the surround.

Dave

Hi Howard,

No I dont have any shim stock and to be honest I am still considering the PTFE shim washers, PTFE is very very low friction and I am just wondering if they will do the job without wearing the alu pulley or the oilite bearing. However from what Jeff explained would PTFE make the situation worse, I dont know.

Ron

Dave,

Yes I have considered laser cutting for all the various grill panels, I am very fortunate in having a friend who can get laser cutting done for me FOC so it would seem the obvious way to go.

Ron

Ron,

Personally I think you are over thinking the situation between pulley and bearing. Firstly the relative rotational speeds are pretty low as are the loadings. If the shaft is to be a soft (say mild steel) material then using hardened washers is likely to have them cut a groove in the shaft over time! Oilite is a bearing material and no reason to suppose that in this 'thrust' application it will be any less efficient than in the normal radial condition. Many thrust bearings are plain bronze with oil lubrication, oilite is a similar but 'self lubricating' material. Your PTFE washer is probably the kindest solution to shaft, bearing and pulley if you really want to control the axial location of the assembly. Lastly I doubt the loco will travel the distance of London to Edinburgh so whatever you do is unlikely to wear catastrophically.

is the TE on the back burner now?

Paul.

Thanks Paul, that was my thinking, the loco wont be doing any marathons and the thrust loading wont be heavy so I thought the PTFE option worth a try.

The TE is on the back burner but not forgotten, in fact I spent some time yesterday evening looking at more motor options. I keep going back to an outrunner brushless as a possibility, if used with li-po packs the batteries could be housed within the engine, still giving it some thought.

Ron