Re: Tim V's workbench - latest shenanigans

[45609]

Hi Tim,

What is the origin of the collet attachment in your Unimat?

Cheers....Morgan

[Tim V]

Standard 8mm WW drawbar, it was sold as an accessory for the Unimat.

[Tim V]

Once the wheels were fixed on, I found that there was still a problem with poor running, I re-centred the coupling rods, using ideas from Chris Pendlenton's article in MRJ 200.

It now runs a lot better, there is a bit of roughness from the three pole motor, I might have a look to see if I can tune that out in the chip.

[HowardGWR]

On the copperclad spacers thanks for the reply Tim. I did try this on one attempt. I fixed the spacers on as per pick up type frame and then I soldered the gapped copperclad to the spacers and then cut through the spacers. Heart in mouth stuff but I got away with it. Nothing must come adrift after that though. Regards, Howard

[Philip Hall]

Tim V wrote:
there is a bit of roughness from the three pole motor

I've just looked at my 45XX chassis and it seems the motor is similar to that in the N. For that I have a replacement Mashima so it might be possible to slot one in if you have no luck with the tuning. I gather there may be problems, though, with getting the worm off and/or the motor shaft diameter.

Philip

[Tim V]

I'm pleased to say that by fiddling with CV9 - the pulse width modulation, as well as CV50 the motor type (Lenz mini silver), I was able to improve the noise from the motor.

All this work was done on a Sprog.

I don't know how DC people cope without this kind of fine tuning!

[Tim V]

I've been making split axles this afternoon.

IMG_0934.JPG

The axles have been turned on the lathe, here I'm about to drill the bleed hole for the Araldite to squeeze out of.

The male halves were turned 2mm diameter, with the hole drilled 3/32" or 2.3mm. There is a spacer washer made from plastic.

[Tim V]

IMG_0935.JPG

The axles have been thoroughly cleaned, including using a clean drill to remove any traces of swarf. A quick dip in an ultrasonic bath pepped them up. Eventually, they were placed in the jig seen here, held together with a 6mm nut and bolt. Plenty of trying them with a multimeter and ensuring they were 22.2mm overall length.

To keep them from sticking to the jig, I used Vaseline on the faces.

The jig was made on the Unimat.

[Tim V]

Unlike my last project engine, I'm using Gibson wheels on my current one.

Problems with Gibson wheels are well known, so we can approach them forewarned. The rims falling off is the main one, though recent batches of wheels are better.

First task is to pop the rims off, on these I easily pressed them out by hand. A certain Gordon Ashton used to pop rims off by putting the wheels into hot water, in this case it cracked the rim!

Once the rim is off, clean up any moulding pips off the centre, and any other flash. As I have a lathe, I've put the centres onto a mandrel, and run a tool over the outside, plus the front. Once all this is done, I'll use my favourite 10 minute epoxy to glue the rims back on.

Why all this fuss? Square round wheels are essential to good running.

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[Tim V]

Starting on the crankpins now. First job, measure up what I want. No scale diagrams here, a sketch will do.

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[Tim V]

Here I'm parting off the crankpin. These blighter's have a habit of falling off, never to be found.

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I just poke a piece of wire into the hole, to keep hold of the turning before it falls off.

[Tim V]

Here, I've turned the crankpin round, to hold it on its running surface. I'm using a pin chuck. I've turned the outer face in this case, and that is a 14BA tap ready to thread the hole. This will NOT be under power of course.

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[Tim V]

Those are the easy crankpins, what about the recessed ones I hear you say
Well, they are made with a cone to match a small countersink, like this.

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They have a slot filed across, so they can be tightened up. Here is one held in an ordinary pin vice.

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The slot is made using this kind of file, this one came from Shesto's many years ago.

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[John Bateson]

Tim - are your crankpins made from solid rod or are you using tubing.
John

[Tim V]

I use 1/8" solid rod, I couldn't guarantee the concentricity of the tube.

I make my own crankpins because it does guarantee that they are concentric, and they can be tightened up properly. My experience of bought in crankpins is that the hole is often oversized, leading to inconsistent throws.

[Tim V]

I don't get on with wiper pickups, I have very few locos with them.

This is a pannier chassis from the early 90s, from a standard Perseverance kit. It was failed at Southampton with dodgy pickups, something my split axle locos do not suffer from.
The starting point.

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Out of interest, here is the top.

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I have put new pickups on the front, but oh dear disaster strikes, the rear board has detached. I'd glued it on!

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Here I have put a new board on, held on with a screw.

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[Tim V]

If I had my way, I'd scrap this chassis and put a proper split axle one on it.

[martin goodall]

If I had my way, I'd scrap this chassis and put a proper split axle one on it.

Every demonstration I have seen of locos with split frame/split axles has convinced me that this is an infinitely superior method of current collection.

The only reason I have never adopted it is that it clearly requires more time and effort to build that type of chassis, particularly when most kit chassis make no provision for a split frame, so that you would have to adapt it yourself (= more work). And then, of course, there is the bother of 'shorting out' plastic centred wheels so as to get the current from the tyre to the axle.

But my main reason for taking Tim up on this is the question of practicality in relation to gearboxes, suspension systems, etc. Just fitting a gearbox in between the wheel bearings can be a struggle sometimes. How do you also fit in the necessary insulation gap without the risk of something bridging that gap and shorting the whole thing out? (There is also the question of how you insulate a centrally mounted compensating beam, although that is probably easier to solve in practice.)

If someone can come up with an easy way round these problems, I would be a happy convert to split-frame current collection. Meanwhile, I remain a somewhat reluctant user of wiper pick-ups.

[Tim V]

Good point Martin.

The Highlevel site gives the width of their gearboxes, I've used the 54:1 usually. Some of the gearboxes are wider, I avoid those.
Left to right are
1. The wiper loco previously referred to, this has a Highlevel 54:1, plenty of room to put split axles,
2. A Highlevel 54:1 on split axles,
3. A Branchlines 50:1 (I think) on split axles, and finally
4. A Highlevel 54:1 on split axles. This is the project Comet prairie chassis from the workbench. Note that the split axle locos look a lot tidier

IMG_0993.JPG

A close up on one chassis, you can just make out the split in the axle, I've used green plastic as a spacer. Gearbox width 8mm, space between my favourite Brassmasters hornblocks, 13mm, so plenty of room. There is a way of making bearings so that wider boxes can be used, but that would need a sketch.

IMG_0994.JPG

Following the success of recentreing the rods on the small prairie, I've looked at one of the Bachman panniers, turns out although the rods alignment very well, the rivet joining front and back was loose, so I'm making a new pivot to hold the rods together. I'm using standard 1/8" alignment jigs, held lightly on with clamps.

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[David Thorpe]

Am I right in thinking that you make your own split axles?

DT

[Tim V]

Yes, shown further up the page.

[David Thorpe]

Yes, shown further up the page.

Sorry, missed that - I was away and when i came back i must have overlooked it.

I'd love to use split axles, but am put off by the unavailability of suitable axles for people who for whatever reason are unable to make their own. I know that Branchlines do them, and the EMGS sells completed split axles, but all are gapped in one place only while if you're going to use them with a gearbox, or indeed any kind of drive, they need to be gapped in two places, and you really need to be able to choose exactly where these places are. Bill bedford produced some good ones, but has discontinued them. Don't suppose you'd like to produce some commercially so that we split axle wannabes can give it a go?

DT

[Tim V]

That is a good point, but I'm sure there is someone local who could knock them up, I'm not set up to produce large numbers of split axles.

I actually only split mine on one side, even on the gearbox axle, I haven't looked at the commercial ones. Perhaps you need to lobby the manufacturers?

By the way the lathe was the best investment I made in the hobby - other than joining the Scalefour Society! And I think my 30 years membership equates to the cost of a lathe.....

[steamraiser]

Scalefour Stores also carry split axles. These give you the option of a three part axle that gives an isolated middle section.

Gordon A
Bristol

[martin goodall]

While on the subject of split axles, my favourite driving wheels (in fact the only wheels I like to use) are Ultrascale. But they have a fairly substantial plastic boss on the back of the wheel. Has anyone used these wheels on a split-frame loco? If so, did you cut off the boss behind the wheel to fit the 'shorting' strip/wire? If not, how would you propoose that these wheels should be treated if/when adapting them for split-frame operation?