EM Bachmann 5MT with Alan Gibson Wheels and Original RTR Motion Gear

[NFWEM57]

I have a Bachmann 5MT which I have been using as an EM gauge test loco for British Finescale 'Easy Build' turnouts.  Only the tender and pony wheels were changed for Alan Gibson ones and I simply eased out the drivers.  It worked until along came the easy build crossings and double slips and it became very apparent that the finer scale Alan Gibson drivers would now need to be fitted.  However, fitting Alan Gibson, or any other, wheels requires a whole lot of change to the motion gear, some quite fiddly.  So, I decide I would replicate the crank pin spigots on the original RTR drivers and fit them to the Alan Gibson wheels.  Then it would merely be a matter of swapping out the RTR drives for the Alan Gibson ones with no change required to the motion gear.  The RTR spigots are all 2.5mm in diameter with a 3.8mm x 0.5mm thick flange and have an M1.4 thread through to the back of the wheel for crank pins bolts / screws.  The front and right hand rear drivers spigots are 1mm tall whilst the middle drivers and the left hand rear driver have 3.5mm tall spigots with alignment slots cut into the top.  The images below show the original RTR wheels which are fitted to 2mm stubs on 3mm axles with a plastic bush to electrically isolate the metal wheel from the axle.

 

  

 

 

To mount the new spigots on the Alan Gibson wheels It is intended to have a 1.8mm diameter x 2.5mm length stub on the back to insert into a 1.8mm hole made in the Alan Gibson wheel where the existing (1mm) crank pin hole is located. The Alan Gibson wheel is shown below.  Note there is no room for a 3.9mm flange and so the flange on the new spigots would be reduced to 3.18mm (1/8") diameter, the size of rod being used to make the spigots. The wheels are mounted directly onto 3mm axles as the wheel centres are plastic.

 

 

 

Although aluminium was first considered to manufacture the spigots, silver steel was chosen in the end to minimise wear.  For tapping the M1.4 threads, an M1.2 hole will be drilled, not M1.1 as recommended for normal 75% engagement, to significantly reduce stress on the tap and which still provides 50% thread engagement; the thread is not load bearing.  Clearly, the spigots cannot be hand made and so will need to be manufactured on a mini lathe.

 

If this solution works it will avoid a lot of pain and grief, as well as cost and time, on a number of other RTR steams locomotives.  Comments and/or advice most welcome.   I'll update as I progress.  Nothing ventured, nothing gained..!

 

Patrick

 

[NFWEM57]

Update..!

 

Had to make a new tool for this project to have any chance of this concept being successful, a spring loaded tap follower that fits in a 6.5mm maximum chuck on the tailstock of my mini lathe. You cannot buy one, they simply do not exist. This one has a reverse centre so that the tip at the back end of the tap fits in to the dimple in the smaller shaft of  tap follower. Had to wait for a few parts to allow me to make it and the last part, the spring, arrives tomorrow.  I shall make the spigots next weekend, fit to the wheel and then do a test run.   It has about 15mm of travel which is ample given the depth of threads involved in this project, 6.5mm maximum.  Less chance now of breaking a very expensive M1.4 spiral point tap.

 

 

Regards,

 

Patrick

Edited December 10, 2022 by NFWEM57

[Izzy]

Unless your using free-cutting N/S I’d suggest either FC steel or brass would be slightly easier to work with, less chance of breaking that tap (although if it’s a machine one (spiral?) should be able to cope), the wear factor being in my experience negligible.

 

Bob

[NFWEM57]

22 hours ago, Izzy said:

Unless your using free-cutting N/S I’d suggest either FC steel or brass would be slightly easier to work with, less chance of breaking that tap (although if it’s a machine one (spiral?) should be able to cope), the wear factor being in my experience negligible.

 

Bob

On reflection you are right, the Ultrascale/Markits crank pins are brass, so I'll start with that. Thank for the advice, made me stop and think..!  Springs arrived, tap follower finished.  

[NFWEM57]

On 10/12/2022 at 18:45, Izzy said:

Unless your using free-cutting N/S I’d suggest either FC steel or brass would be slightly easier to work with, less chance of breaking that tap (although if it’s a machine one (spiral?) should be able to cope), the wear factor being in my experience negligible.

 

Bob

On reflection you are right, the Ultrascale/Markits crank pins are brass, so I'll start with that. Thank for the advice, made me stop and think..!  Springs arrived, tap follower finished.  

[NFWEM57]

Update

 

1/8 inch brass rod arrived and 2 styles of crankpin spigot manufactured on lathe.  Machined first before tapping M1.4 on the lathe using a spiral point tap and the spring loaded tap follower; went through like butter.  Flange dimension 3.18mm, connecting rod 2.5mm and insert into AG wheel, 1.8mm. 

  

Next jobs are to cut alignment slots in central spigots, drill out holes in AG wheel to 1.8mm, fit the spigots in place using Loctite 243 and fit balance weights.   Need to give a final deburr to the brass spigots. Might try mild steel for the next set.  Finally, mount wheels on 3mm axles and refit to loco.  Lathe used is a Proxxon FD150/E.

[NFWEM57]

Update.

 

Revised flange dimension and machining for bushes (to give them their correct name) and now have 3 short and 3 long bushes to proceed with the conversion.  Manufacture of short bush (4mm long) shown below.  First image is the raw 1/8" rod around 5mm in length.

     

 

Placed in appropriate collet and machine to 1.8mm diameter and 2.3mm length (the width of an AG wheel).

 

 

Reversed in a smaller collet and then reduced to 1.7mm length and the final 1mm reduced in diameter to 2.5mm.

 

 

 

Next, drilled through with 1.2mm drill (50% engagement) and then tapped with an M1.4 spiral point tap.  i used the tail stock of the lathe to hold the spring loaded tap follower and to rotate the tap I simply put it into the centre of a 3 section connecter block. Not my idea, got it trawling the web. brilliant, no excess lateral force on the tap, just rotational. 

 

  

 

Next step is to cut alignment slots in the long bushes and then fit to the AG wheels.

 

 

Good progress so far.   Hope to have the 5MT running by the weekend.

 

Patrick

Edited December 19, 2022 by NFWEM57

[NFWEM57]

Alan Gibson crank pin holes drilled out to 1.8mm and brass bushes test fitted. Critical to ensure drill is vertical when drilling.  I drilled out initially with a 1mm drill then used a 1.8mm drill.  Obviously these will not fit a GW wheel press with these bushes so I will permanently fix the bushes and balance weights once the axles have been fitted.

Yet to cut slots in longer bushes, this will be done before fitting once each axle set is assembled.

[ikcdab]

You have done some excellent work there. Very fine.

But I question the original premise.  I have handbuilt track.  16.5mm gauge with 1mm flangeways.  All my modern Bachmann and other RTR locos run through these ok.  So I am wondering why your Bachmann drivers would not fit through the easybuild turnouts?

Ian

[NFWEM57]

On 21/12/2022 at 18:54, ikcdab said:

But I question the original premise.

Hi Ian. 

 

Thank you for your compliment, interest and question.  I am using EM gauge easy build turnouts. On my original EM gauge test track I used B7s and the 5MT with original wheels just pulled out worked fine.  However, when I tried with the double slip the flanges are just too big at 0.9mm depth and there is a noticeable bump as the loco passed over certain part of the turnout.  On closer inspect of the turnout there are raised  parts, necessarily so for mechanical reason, in certain areas.  Running a set of EM gauge wheels through the slip, which have a flange depth of 0.6mm, there is no such bump.   So, I bit the bullet and decide to have a go at using AG wheels with original motion gear.  If this works then I have a solution to a number of steam locomotives conversions I need to undertake,  Diesels are all converted, thanks to Ultrascale for the most part.   

 

Hope this clarifies.

 

Patrick

 

 

Edited December 23, 2022 by NFWEM57
typo

[Izzy]

Hi Patrick,

 

I know you've done this now, but have you considered just skimming the back of the Bachmann wheels to reduce the flange width and also the depth. I've converted a Hornby J15, Oxford N7, and Bachmann 03 to P4 this way. Okay, I've also thinned some of the wheels a bit but that's not neccesary for what you're doing - well I don't think so. I've also used this method to 'P4' all my rolling stock wheels of one make or another. It's just a thought.

 

Bob

[NFWEM57]

On 21/12/2022 at 19:46, Izzy said:

have you considered just skimming the back of the Bachmann wheels

Hi Bob,

 

Thank you for your advice. Yes, I did consider it but in the end decided against it for this conversion.  However, I have have some other wheel sets which are suitable for this approach.   I have also come up with a way of holding the wheels in a lathe without damaging the plastic centre boss or distorting the wheel due to clamping.  I'll  start a thread when I come to converting a set.  Once I have the 5MT running nicely through the EM turnouts I can an restart another delayed project which will required the wheels to be machined, a Lima HST conversion using the latest central mounted motor and driven bogies.  I converted a Hornby one earlier in the year but the flanges will need reducing from 0.95mm to about 0.6mm given the turnout issue.  Threads on both are live and conversion instructions for the Hornby one in the relevant thread.

 

Patrick

Edited December 23, 2022 by NFWEM57
typo

[Captain Kernow]

On 21/12/2022 at 18:54, ikcdab said:

You have done some excellent work there. Very fine.

But I question the original premise.  I have handbuilt track.  16.5mm gauge with 1mm flangeways.  All my modern Bachmann and other RTR locos run through these ok.  So I am wondering why your Bachmann drivers would not fit through the easybuild turnouts?

Ian

A few years ago, I was considering re-wheeling a Bachmann 5MT, using Alan Gibson wheels, only this would have remained an OO loco. The reason was due to the Bachmann flanges bumping along the tops of the chairs on C&L OO bullhead track. I obtained the wheels for the 5MT (and also for a Bachmann 'Crab', which exhibited the same problem), but in the end I never proceeded with either project and the locos eventually got sold (I already had another 5MT built from a DJH kit with Markits wheels anyway).

 

I remember ringing up Alan Gibson himself to order the wheels and he was initially bemused as to why I would want a set of his conversion wheels, if I wasn't going to convert the loco to either EM or P4!

 

The inconsistency in Bachmann's steam loco driving wheel flange depths has always been a mystery to me. Other Bachmann steam locos, such as a WD 2-8-0, GW 57XX pannier etc. all have finer flanges, which don't give any problems.

 

[NFWEM57]

6 hours ago, Captain Kernow said:

inconsistency in Bachmann's steam loco driving wheel flange depths

Hi, 

 

Thank you for your interest and I agree, makes no sense.  It is very much a case of examining each model and seeing what can be done. 

 

As I type, the 5MT chassis is running round my test track 'bedding in'.  A couple of minor hiccups on the way and more lessons (re) learnt.  The first was not checking the rear left driving wheel bush size, it was different but I simply reduced the height of the long bush.  The second was to find that whilst the eccentric crank screw is M1.4, the other bolts appear to be 12BA, so a quick fix there using M1.4 screws and M2 washers for now.   I also reduced the height of the front bushes from 1mm to 0.5mm to provide more clearance for the connecting rod.  I modified my GW wheel press to allow the new crank pin arrangement to fit when assembling and quartering the wheels and axles. 

 

Chassis runs through the double slip fine but I'll post more on that on the "Using the easy-assembly Finetrax pointwork kits in 00 and EM" thread.

 

So, the concept works aside from a few minor issues with bolts sizes.  I'll upload more details post the Christmas days.  Once I get a few postposed projects out of the way, I will be converting a split chassis 4MT and a split chassis A4 to EM using the same process.

 

Have a great festive break.

 

Patrick

Edited December 24, 2022 by NFWEM57
clarity and typos

[NFWEM57]

Final Update

 

The locomotive has now been put back together, balance weights added and following bench testing will be run through the British Finescale test track today.  Both sides of the locomotives are show below.

 

 

 

The original screws are in the central driving wheels, the speedo screw was lost but more are on the way from Bachmann.  M1.4 screws with M2 washers have been used on the front driving wheels and the rear right hand driving wheel.  Wheel rims, axles and and Phillips screws will be blackened when the Carr's Metal Black for Steel arrives.

 

If required, I might add an M2.5 spacer between coupling and connecter rods on the middle drivers just to keep the coupling rod clear of the front wheel crank.

 

I am awaiting some 12BA bolts to satisfy the theory that the original RTR wheels used 12BA bolts.  If proven, then a 12BA spiral point tap will be ordered so that future conversions can use the original bolts.  The original bolts are 2.5mm across the flats and 2.8 across the corners.  The only M1.4 bolts I could find are 2mm across the flats and so too small; as are M1.4 screws, hence the washer.

 

I will upload a video of the track test this afternoon to the British Finescale thread.

 

Following the long overdue Lima HST conversion, I will be tackling a split chassis 43xx, an A4 and a Hornby Rebuilt West Country.   I will be using spring pickups on the split chassis locos.

 

Overall, a success I think.

 

Patrick

 

 

Edited December 31, 2022 by NFWEM57

[NFWEM57]

Video Published

 

 

[NFWEM57]

Quick Update on Bolts

 

I can only assume that I may have crushed the thread when manufacturing one of the early bushes and that is why the bolts would not go all the way through.  Changed the machining order for the last few bushed and drilling & tapping was the last stage.

 

12BA bolts arrived today, they slide straight through the tap on a RTR wheel.

 

So, problem solved, all threads are M1.4.

 

Happy New Year,

 

Patrick