EM Hornby Railroad HST - Conversion

[NFWEM57]

Having converted both an early model Hornby HST and a Lima HST to use the new powered bogies and central drive motors, it occurred to me that, for the prototype, later HSTs sets had fewer coaches, say 4 or 5.  Therefore, a Hornby Railroad HST might well be capable of hauling a reduced number of coaches.  At £140, the R1230M set which includes a pair of DVTs and a coach (plus a controller, oval track with siding and a track mat) might be a worthwhile candidate for upgrade and conversion to EM.  A used set, minus the additional items, was acquired for £110; the coach will be sold on.

 

The requirements for the conversion are:

•   DCC Decoders in both cars including pickups on all bogies.
•   Correct running lights.
•   Cab lights.
•   Additional decals.
•   Semi-gloss coating to match ‘high end’ coaches.
•   Improved couplings.

EM gauge using wheels without traction tyres; X9861 suitable replacement.

 

Initial research indicates this will be a very simple conversion..... !

 

Patrick

Edited February 6, 2023 by NFWEM57
typo

[NFWEM57]

First look at Power Car

 

The power car weighs 320g, quite substantial already given the full fat HST weighs 520g.  With the body shell removed the chassis looks like this.  Driven bogie at the rear.  Air tanks and cabin insert as for the Lima model.  There is room for a modified electronics raft at the front with a decoder socket, or the existing decoder socket may be used.  The speaker could be mounted above the ballast weight and a stay alive can be fitted a the rear.

 

 

The wheels are smaller, 11.5mm, and mounted on 2.5mm to 2mm stepped axles.  The ride height is therefore lower with the nose of the HST some 1mm under height from the rail head; 19mm vice 20mm for the prototype.  The full fat HST wheel size is 13.5mm and also has disc pads.  Simply replacing the wheels corrects the ride height and gives a better look.  Front bogies shown below, left, and with a full fat HST wheel for comparison, centre and right.  For EM gauge conversion, stepped axles will be used purchased from the EMGS.

 

     

 

As the chassis and cab insert are as for the Lima model, the Black Cat module can be used.

 

 

The target is for the modified loco to haul up to five Mk3 coaches.  A little additional weight might be added, say 50~100g, if needed.

 

Patrick

 

Edited February 7, 2023 by NFWEM57

[NFWEM57]

Donor Wheels and Axles

 

If staying with OO the existing axles can be used with the donor wheels.  For EM gauge it is a little more complicated.  Note: both original and donor wheels are live axle which might making pickup arrangements a little more easy but I prefer all wheel pick .  The EM gauge conversion is as follows.

 

The tyre width of the donor wheels is 2.75mm which, with a back to back of 16.5mm, means the fact to face dimension is 22mm.  The free space inside the bogies is 23.75mm so there is ample clearance.   The 2.5mm to 2mm step axles purchase from the EMGS have a shoulder dimension of 16.5mm.  However on the back of the donor wheels there is a hub of 0.45mm depth for the all metal wheel and 0.7mm depth for the plastic hub wheel which means the minimum back to back with an unmodified axle is 17.65mm..!  Plastic hub left, new EMGS axles middle and metal hub right.

 

 

With the overall axle length of 23.2mm, the length needs to be reduced to 22mm and the 2mm stubs need to be 3.45mm thus reducing the shoulder dimension to 15.1mm.  To avoid too much work only one end of the axle is modified, the existing stubs being 3.35mm, and so one end of the axle is reduced in length to make the overall axle length 22mm and the remaining shoulder (reduced in length to 2.15mm due to axle length reduction) is increased again to make it 3.45mm.  The shoulder dimension is then 15.2mm which with sets the minimum back to back of at 15.2mm plus 0.7mm plus 0.45mm which is 16.35mm; so a little room for adjustment.

 

There is no point in adding washers to either side as side play is limited by the bogie frame, as per the original Hornby Railroad design.

 

Finally, unlike the full fat HST which has pinpoint axles on the dummy car, the railroad version uses the same axle set up as the power car.   Makes life easy.  This wheel conversion covers both dummy car bogies and the front power car bogie.  I'll outline the changes to the driven bogie separately. 

 

Patrick

[NFWEM57]

Good News and Bad News

 

Good News

 

Before starting the conversion in earnest I though it would be wise to check the load capacity.  The power car successfully pulled an OO gauge 5 car formation of Mk3s and the dummy car. 

 

Bad News but with a solution..!

 

Having converted the 3 unpowered bogies to EM with the correct size wheels, I started the powered bogie.  It is difficult to detach the baseplate which is retained with 4 clips on the side.  I started from the front part of the bogie and eventually managed to unclip the baseplate.   There looks to be an access hole for a special tool on one side as the adjacent holes are larger on one side than the other; see images below.

 

With the the gears (carefully) removed from the original axles, they were placed on the new axles which had been scored in the centre region with the edge of a file and Loctite 243 used to secure in place.  The problem then is the casing for the motor fouls the larger wheel. For EM gauge some fettling was required to achieve a little side play and clearance. For OO, it will be necessary to cut out part of the motor casing to achieve clearance.  I have undertaken the same even thought it is for EM gauge.  not much needed to be taken off to get OO clearance, just the corners.  I used a Japanese saw  being careful to mind the clips for the bottom of the bogie.

 

    

 

I guess there is no such thing as a free dinner...!!!!!!!  So, a little more effort that first thought.  Finally, the power bogie axle holes are a little tight.  The original axles were 1.48mm, the new ones 1.50mm, a few passes of the file in the axle slot to slightly widen, not deepen, solved the problem.  Check free play of the axle before fitting gear and wheels.  Brass bearings might be fitted to the next conversion as I recall the early Bachmann Class 46s having issues with a similar slot arrangement.  Will use a broach to widen the slots to 2mm for a brass bearing, 2mm outside diameter, 1.51 inside diameter. 

 

The pickups need to adjusted to match the new wheels or replacement pickups used.

 

Next is rewiring the bogie and NEM862 interface using DCC colours followed by a DC test run of the power car on the EM gauge test track.

 

Patrick

Edited February 11, 2023 by NFWEM57
added additional info

[NFWEM57]

After considering several options, the internal layout for the electronics has been decided upon.  All the existing internal electric are removed and a bespoke PCB designed complete with NEM 862 socket which will provide for a direction sensitive switchable and adjustable cab light, via Aux 1, independently adjustable supplies for the running lights and marker lights and part of the stay alive circuit.  The stay alive capacitor is mounted at the rear and a medium megabass speaker is mounted on 10mm brass standoffs above the front bogie.  A mini break out PCB can be fitted below the speaker for the late HST lighting configuration which will use bicolour SMD LEDs with micro litz wiring.   The weight retainers on the glazing insert are not required, the weight is already 'glued' in place, and will be removed to make space for the bespoke PCB.  The TTS decoder will sit inside the void vacated by the NEM862 socket behind the speaker.

 

 

 

Just waiting for the arrival of some 10mm brass standoffs and then work can continue.  The dummy car will be wired the same and pickups added to the bogies.

 

Patrick

 

 

[NFWEM57]

Update

 

The power bogie revealed further challenges as it was rewired and reassembled.  Unlike the unpowered bogies, (left) the front and rear of the power bogie frame foul the wheels (right) and so had to be cut out and will need to be replaced with a thin cosmetic addition.

 

 

 

For lighting, instead of using the Stickswipe module. a bespoke lighting solution was developed as independent adjustment of running and marker lights brilliance was required.  Micro litz wired SMD LEDs were glued (epoxy resin) to a 1mm thick strip of plasticard which sits under the cab front with the LEDs connected to a breakout board which sits under the cab insert which, in turn, is collected to the main PCB.

 

    

 

 

The speaker is mounted on four hex M2 standoffs and the bespoke PCB is mount on top of the weight.  The TTS decoder, which has had a negative stay alive lead fitted, is placed in the void which used to house the NEM652 socket.  Finally, the stay alive capacitor is mounted at the rear of the chassis.  The glazing insert requires a little modification to allow refitting.  the 3 trimmers on the main PCB are for adjusting the brilliance of the running lights, marker light and cab light.  The cab light is enabled using Aux 1 and is direction sensitive

 

   

 

 

The unpowered car has the same PCB and lighting arrangement, stay alive and has pickups added to the bogies.

 

As Hornby TTS decoders only work using basic consists, i.e. both cars with the same address, some sounds for the dummy car decoder have the volume reduced to zero.  These include all horn sounds, cab door slam, driver safety device, wipers, AWS, fire bell and guard to driver buzzer.

 

The power car has been run in for 30 minutes each way at moderate speed and runs smoothly.  Once the dummy car is complete and the GWR Mk3s converted to EM gauge with new wheel sets I will upload a video.

 

Total weight of power car is 350g which is adequate for the planned 5 Mk3 rake.

 

Patrick

 

 

Edited February 24, 2023 by NFWEM57
added additional info

[NFWEM57]

Update

 

Load test failed.  I tested the HST set with 5 Mk3 coaches before conversion from OO gauge test track and there were no issues.  Once converted, the power car has wheel slip with the rake and will only handle 2 coaches.  Will need to check rolling resistance for all coaches and the dummy car.  Mk3s have been fitted with Alan Gibson 12mm disc wheels and are free rolling but will undertake a rolling resistance check although, after conversion, the bogies all began to roll freely on my bench which has a 1.5 degree slope (0.25%); not by design. Might add 50-100g of lead to the power car if rolling resistance checks finds little or nothing to adjust.  Bit surprised given the trial result when all the stock was still OO gauge.

 

Conclusions on the Railroad conversion thus far.

• Wheel change not possible for OO and difficult for EM for the Class 43 Railroad Bogie.
• More time/effort than Lima conversion using latest bogies and central drive motor.

For interest. I have several Lima Class 47s and Hornby Class 37s to convert using Railroad bogies and none will have the problem with wheel size; it is just the legacy of undersized wheels with the Lima HST tooling which has caused problems.

 

I shall persevere..!

 

Patrick

Edited February 27, 2023 by NFWEM57
typo

[NFWEM57]

The Traction Issue

 

Decided to approach the problem from a more 'scientific' angle and measure overall loco weight, weight on each bogie and drawbar pull at wheel slip and full power.  Tested the recent EM converted Lima HST with both bogies driven and a central motor, the original Hornby Railroad HST, the EM converted Hornby Railroad HST and the same with additional weight.  I used a pair of cheap (0-500g) mini scales to measure weight on each bogie and a cheap spring balance to measure drawbar pull at the point the wheels slipped and (briefly) at full power.

 

Rule of thumb, based on coefficient of friction, is that 20~25% of a loco weight is the drawbar pull for metal wheels on rails which increases to 75~80% for rubber on metal, i.e. traction tyres.  The other complicating factors are the number of driven bogies, 2 for the Lima HST and one for the railroad HST and the fact that, by all accounts, DCC operation results in slightly lower maximum power in comparison to DC operation. (check out Chadwick Model Railway video 152 for a demo).

 

The results were, read as follows - Loco Type, Loco Weight, Front Bogie Weight, Rear Bogie Weight, Wheels, Power, Initial Drawbar Pull, Drawbar Pull at Max Power:

 

Lima EM HST Conversion with central motor and 2 driven bogies - 410g, 189g, 221g, metal,  DCC, 70g, 120g

Original Railroad HST - 310g, 136g, 177g, metal with traction tyre, DC, 70g, 120g 

Converted EM Railroad HST - 347g,  157g, 190g, metal, DCC, 20g, 28g

Converted EM Railroad HST with additional weight - 420g, 167g, 253g, metal, DCC, 35g, 40g

 

Conclusion

 

If you wish to retain the pulling power of the Hornby Railroad model for an EM conversion it would be wise to use 13.5mm wheels with traction tyres; if you can find any, and any with disc pads..! Unlikely.  As it stands the Railroad conversion only has 33% the pulling power of the original and that is reluctant to pull the dummy car, let alone coaches...!  The motor is just not powerful enough for metal on metal traction.   One solution would be to fit another power bogie but given the effort and butchery require to fit EM gauge wheels, the only solution would seem to be to undertake a full conversion of both cars (to standardise bogies) as already undertaken for the Lima Blue Grey.  Most of the work is already done, bespoke PCB, light module, etc.  Just a few modifications to a replacement chassis to fit new bogies and a central drive motor; already in the spares box.  For the donor, I will refit the original wheels to the bogies, make both cars DCC ready with full lighting and cab lights and sell on..!

 

As someone (Elon Musk) once said, 'If you are not failing, you are not innovating enough'.  Hope this thread has proved useful.  Despite the failure it was interesting and allowed me to set up a system to measure the spread of weight and pulling power for future conversion, many of which will be steam.

 

Patrick

 

PS:  I was about to convert some Hornby Class 37s and Lima Class 47s using Railroad Bogies.  Whilst the wheel size is the same, so no butchery needed for EM gauge, I wonder now if 2 powered bogies will be required per locomotive and if even that will be sufficient given the motors and gears are the same as that in the HST and the Class 37/47 bogies only have 2 driven axles so the best we might expect is 80g maximum with 2 bogies; which is pretty poor.   Guess the only way is to test....  Perhaps a thread on railroad bogies capability, original and converted is required?

 

Is there anybody making replacement bogies with a bigger motor??!!  Not really, not even Penbits. Other options are to fit the original Hornby/Lima Bogies with CD motor conversion but the 6 wheel conversions are pretty underpowered as only a 6V CD motor can be used. 

 

Edited March 1, 2023 by NFWEM57
Additional Info

[NFWEM57]

Change of plan re Hornby Railroad Bogies

 

So, even Hornby staff will not buy locomotives with traction tyres..!   It is not viable to fit Hornby Railroad bogies with all steel wheels, they end up with the pulling power of a gnat.  Avoid.

 

I have decided to convert my Lima Class 47s in a very different way, a thread will follow; they will have the pulling power of an Ox...!  The very early Hornby Class 37s will be sold on but with significant improvements.

 

 Thank you for watching, the feedback and the comments ..!  No more updates to this thread from me.

 

Patrick

Edited March 2, 2023 by NFWEM57

[TimberValleyRailway]

This is very interesting - I own a RR HST and am looking to make it more realistic - particularly in the lighting department. This has provided plenty of useful information, thanks!

 

Best Wishes

[NFWEM57]

On 04/07/2023 at 15:40, TimberValleyRailway said:

I own a RR HST and am looking to make it more realistic

Hi, thank you for the comments.  Project overall was a failure because the railroad power bogie without traction tyres just cannot pull anything. 

 

You may wish to look at my other conversion for the Lima HST Conversion for some more ideas. You could certainly make use of the electrics and stay alive.