Heljan class 45/0, conversion to S7

[RichardG]

Another person has asked me about the plating on the tyres.

The factory wheels carry chemical blackening on their fronts and backs, and a steel-like colour on the running surfaces of the tyres. I initially thought that this steel colour was a chemical treatment, but it eventually revealed itself to be a plating.


The plating is incredibly thin - perhaps a third of a thou, so 0.0003 in or 0.01 mm.

I don't imagine the plating wearing very well, and I want my wheels to run concentrically and to have matching diameters. I have therefore chosen to turn the all of the tyres down to the bare brass. This leaves me to re-colour the wheels later.

 

[mickoo]

I'd like to see how the two-handled hammer is used. Never seen such a thing before.

I appreciate that might be more Tony's world than Richard's...

Just to cut in (but no one to shreads) said two handled hammer used at the turn of the century to aid chain making and other heavy smithy work, odd, but they do exist.

 

[Eastsidepilot]

Richard, this may be of interest, it was an earlier thread of mine back in 2017

Converting RTR Wheel Sets to S7 or Any Other Profile

Here is a sequence of converting some RTR wheels to S7 but can be to any profile as required. Firstly pull the wheels from their axles. If you don't have a puller they can be removed by tapping the axle through with a punch whilst supporting the wheel over the vice jaws. Measure the tyre...

www.westernthunder.co.uk

Col.

 

[RichardG]

Yes Col. it is a very good post.

I have been doing some things slightly differently. For example I have removed excess wheel thickness from the front as well as the back. I'm not sure whether one way is "better" than the other - we can best compare notes after I post the details.

If you don't have a puller they can be removed by tapping the axle through with a punch whilst supporting the wheel over the vice jaws.

I will suggest, very tongue in cheek, I guess you use a miniature hide mallet to tap the punch? Nothing quite as robust as a ahem hammer

 

[Emma H]

I have just finished turning wheel 11 out of 16 . . .

Can I ask what size/make of lathe are you using?

 

[RichardG]

Can I ask what size/make of lathe are you using?

Of course - it is a Cowells ME90, bought secondhand and probably around 35 or 40 years old.

The wheel profiling is the most arduous thing I have done on it, and sometimes I have wondered if could ever get enough pressure out of the tailstock spindle. When this happened, I took out the wheel, degreased all the mating surfaces, and tried again. My gut feeling is, I am nearing the limit of what this machine can cope with. Then again, the Heljan brass is horrible to turn, it keeps grabbing and chipping and flaking. A steel wheel e.g. Slater's would turn much more freely.

I have had the machine for a few years and I did a lubrication service on it a few weeks ago - see
Lubrication service on a small lathe
for plenty of photos.

 

[RichardG]

Special Tools.


These are the special tools I obtained and made to do the conversion.

Clockwise from the back:

• A loco servicing cradle, improvised from a length of Nomapack U 60-80. I don’t know what this channel is made for, but to me it looks like protective packing for a uPVC window. From the ScaleSeven Group at Albury.
• A wheel puller, improvised from a small G cramp.
• A nail punch, with the business end turned down to be a loose fit inside the bush of a Heljan wheel.
• A wheel profiling tool, from the ScaleSeven stores.
• Two mandrels and a pressure pad, turned up on the lathe.
• A back-to-back gauge, also turned up on the lathe (commercial equivalents are available).

Two slightly tired mandrels.

• There are two mandrels, one for each size of wheel. Each mandrel is turned from aluminium bar, with a steel axle from a child’s metal construction set.
• The reduced end of the axle is a light press fit into the bush of a Heljan wheel. By light press fit, I mean that I can feel friction but no resistance; and there is no discernible free play.
• The axle is an interference fit into the mandrel, assembled in the lathe as a permanent fixture. For me, the lathe has sufficient strength to do this, the drill press does not.

Pressure pad.

• The pressure pad is small enough to let a cutting tool skim the front of the tyre.
• The “wheel” side (shown here) is concave to clear the hub of the wheel.

Example arrangement of mandrel, wheel and pressure pad.

When the second bogie was underway, I started to use a couple of 1/4 inch drive sockets in place of the pressure pad. They clamped the wheel more effectively than the pad I had made myself, and so a mixture appears in the photos.

Your wheels are indeed looking very good, but I know from experience that the most difficult task with this is getting the wheels back on the axles without a wobble.

To begin, I am using only one back-to-back gauge.

• My gauge is as close as I can make it to 31.25 mm, certainly somewhere between the limits of 31.2 and 31.3 mm allowed for ScaleSeven.
• The limits of the allowable back to back dimension (+/- 0.05 mm) emphasise the importance of not having wobbly wheels.

If the rebuilt locomotive does not negotiate pointwork correctly, I can revisit this gauge and maybe make a second one, so I have a go / no-go pair.

 

[Ian@StEnochs]

Richard,

Wheel re-profiling is one of those tasks that, once you are confident in the process, one does on autopilot. As I use a chuck with soft jaws for holding wheels while the thickness is reduced I like to do as many as possible at the one setting before mounting the dedicated size mandrels for the final form tool shaping. All wheels the same size end up exactly that. My last job was tender wheels when I did enough for 6 locos worth, I got through a couple of Sherlock Holmes stories on the player in that session!

You may not have considered it but I mount the form tool in a rear tool-post upside down. That way the swarf falls away from the cutting edge rather than build up and you can mount another tool to do the front tyre chamfer on the top slide without having to remount the wheel later.

Ian.

 

[JimG]

Of course - it is a Cowells ME90, bought secondhand and probably around 35 or 40 years old.

The wheel profiling is the most arduous thing I have done on it, and sometimes I have wondered if could ever get enough pressure out of the tailstock spindle.

Are you using backgear? I've turned and formed 1/32 scale wheels on my ME90 with little problem. The tyres were mild steel and I used backgear.

Jim.

 

[RichardG]

Are you using backgear? I've turned and formed 1/32 scale wheels on my ME90 with little problem. The tyres were mild steel and I used backgear.

Yes I am using the backgear. In my case with the pulleys were giving the fastest drive so 180 rpm.

My struggle was with the wheel flanges, where the profile tool kept snagging and stopping the wheel. This was worse with the smaller wheels than the larger wheels, which surprised me. When the profile tool reached the running surface of the tyre, everything settled down and the cutting was much smoother.

The circumference of the flange had been left quite sharp by facing the back of the wheel. Maybe I should have smoothed this down before starting with the profile tool.

Facing the fronts of the wheels (using a standard left-hand cutting tool) was straightforward.

I turned some Slater's wagon wheels as a practice piece and these were easier.

 

[MarkR]

I got through a couple of Sherlock Holmes stories on the player in that session!

Ahh! "The Red Headed League", and "The Engineers Thumb", cracking good stories!

 

[JimG]

Yes I am using the backgear. In my case with the pulleys were giving the fastest drive so 180 rpm.

My struggle was with the wheel flanges, where the profile tool kept snagging and stopping the wheel. This was worse with the smaller wheels than the larger wheels, which surprised me. When the profile tool reached the running surface of the tyre, everything settled down and the cutting was much smoother.

It looks like you have got a pretty bad brass alloy as the wheel rims - probably a very hard variety to minimise wear on the wheel tyres. If it were me, I would have turned the brass tyres off and fitted, and turned, steel tyres using a nice free-cutting steel. But I'm a bit late suggesting that. And sourcing steel tyres, if a thick-walled tube is not available of the correct size, can be a bit of a pain, usually requiring the making of blanks from rod and trepanning the centre out.

I did, some years ago, get a bit of steel bar offcut from a friendly engineering firm for my 1/32 scale drivers. The really friendly bit was the person on a very large lathe offering to put a 1 1/2" drill though the offcut to save all the boring or trepanning.

Jim.