New Hornby Terrier Conversion

[John CutlerParticipant]

I succumbed to an August sale offer for the newly tooled Terrier for £65.
Now I am wondering how or even if to convert it to EM!

It seems to me that there are 2 options:
1. Try and replace the Hornby wheels and axles. This gets rid of the horribly oversized crankpin nuts and would keep the chassis which has cleverly retained brake gear which looks delicate but is remarkably resilient. I do not think merely opening out the Hornby wheels will work because of their thickness; the splashers need thinning too much methinks (an extra 0.4mm each side). The Hornby axles are 2.2mm diameter running in 3.15mm o/d bearings in a mazak-type chassis. A straightforward swap for Alan Gibson wheels will not work.
2. Replace the chassis with the Branchlines offering. I have one made up several years ago for a split-frame experiment
on an old Terrier body (condemned as the epoxy used to glue a lump of lead in the smokebox caused the chimney to lean at a decided angle after a year or so!). This chassis can be made to fit and has the advantage that piston cylinders and air cylinders can be modelled where the Hornby chassis coupling pockets obstruct the possibility of these fittings. However the underside of the boiler will be lost. An unexpected disadvantage of the Branchlines chassis is its weight. Mine (including 1420 motor) weighs in at 48 grams compared to the 64g of Hornby’s. Not much difference you might say but the new Terrier body is lightweight at only 48 grams. The old one stuffed with lead comes in at 76g. A small loco like this needs all the weight it can muster (yes, more can be put in the decoder space).

Both options require careful (i.e. scary) widening out of the wheel splashers.

I have asked Colin Seymour of Alan Gibson if he has any plans to supply wheels and axles for this.
I will post his reply.

Has anyone tried a conversion?
Any thoughts are welcome!

If al else fails, a dockside diorama in OO will be the answer!

Thanks
John C

[John CutlerParticipant]

Colin Seymour has replied promptly, to his credit.

Unfortunately he has no plans to produce wheels with 2.2mm axles in the near future.

So a new chassis is the only option I am aware of.

John C

[John CutlerParticipant]

1/8″ axles will fit the chassis if the Hornby brass bearings are dispensed with.
This means the axles run in the mazak chassis.
Not good engineering but many old models run like this and survive.

Will try.
But am hedging my bets by acquiring a Branchlines chassis kit.
This has a possible advantage over the Hornby chassis in that it can be sprung or compensated.
The Hornby chassis is rigid (OK, almost rigid!).
An issue will be loading up a new chassis with lead weights!
A project for later methinks.

[John CutlerParticipant]

This turned out to be a prolonged job!

The Terrier splashers need to be widened carefully. I managed to stop filing just in time, although a scratch is visible on the front splashers. A P4 conversion will be tight. Filing out the splashers exposes the metal footplate (which is hard going!); this needs to be insulated from the widened wheels. I covered with a thin layer of acrylic paint but thin sellotape cut to shape might be better.

Alan Gibson’s wheels for the Terrier gave me more trouble than usual. The holes for the crankpin are not ready moulded or drilled. A very faint depression marks the crankpin location. It is very easy to drill off location and one wheel duly fell victim. I used a long crankpin bearing to try and keep the (0.7mm) drill vertical and this worked surprisingly well. Having drilled through, I made a thread by screwing a crankpin from the front of the wheel, followed by a 2.3mm countersink of the hole at the rear of the wheel to allow the crankpin screw to seat. The screw was secured with a spot of superglue before tightening into place.

The gear from the Hornby wheels needs to be reused. This should be knocked or squeezed out of the Hornby axle, not twisted out. The Gibson axles should be prepared; I recommend smoothing out the chamfer on the axle ends and using fine wet-and-dry abrasive paper to try and eliminate any possible sharp edges on the ends. The Gibson axle for the drive needs to be carefully marked out for the position of the gear wheel. There is very little room for error; clearances are tight. Measure everything up with spacing washers in place on the chassis. The rear driving axle needs to be a fairly tight (but running) fit with no side play so the new gear wheel cannot foul. I abraded the gear wheel position with a file rolled across the axle but did not apply any glue (as an extra safeguard) until I was 100% happy with the final gear wheel location. Remember to slide the gear onto (and off) the axle; do not twist.

The rear driving axle should therefore have little side play. It is desirable to minimise the sideplay on the front wheels as well; this minimises the filing of splashers required. I used 2x 1mm and 1x 0.5mm EMGS washers each side for these axles. Note these gave 2.8 mm of washer each side; the washers are each 0.1mm overthick according to my vernier. Do not just accept the product descriptions, measure these things yourself! The centre axle needs sideplay to allow transit through curves; I used 2x1mm washers each side. Note I aim for a Back-to-Back in the range of 16.5mm to 16.7mm.

I used a GW wheel press to quarter and press the wheels onto the axles.
Unfortunately I failed to prepare the wheels sufficiently and ended up applying too much pressure. The result was an unacceptably wonky set of wobbly wheels. From experience there is no point in trying to rectify this so all were scrapped and a new set purchased. The second time I spent more time smoothing the axle ends and put a tiny countersink on the wheel face with a 3.5 mm drill. Someone (the original Mr Alan Gibson?) in the distant past recommended wetting the axle ends with spit to help. This worked but there is still a small amount of wobble and I pray for the day wheels with stub axles or similar are produced.

The 1/8” axles are reasonably free-running in the mazak (?) chassis and I applied a spot of clock oil to each bearing point. Maybe Teflon grease would be better? Fortunately the brake blocks need no adjustment; clearances are OK. The Hornby coupling rods can be re-used and are a surprisingly good fit on the Gibson crankpin bearings.

I was not at all happy with the Hornby pick-ups. Out-of-the-box running on OO track was jerky and even after adjustments to the pick-ups, was not smooth.
There was no way pick up from the centre axle was going to be reliable given the wider EM back-to-back and sideplay. So a piece of 0.4mm PCB was wedged between the centre springs under the keeper plate. This was soldered to the bent-back central pick-ups and 0.3mm phosphor bronze wipers formed to lightly rest against the wheel flanges.

The result is acceptable but I cannot help feeling Hornby missed a couple of tricks in not having a heavier body and not having a spring on the centre axle. I attached extra weights in spaces in the side tanks and also in the screw holes. But this only adds a few grams. I used Blu-Tak as a semi-permanent adhesive. I had a bad experience of a warped smoke box resulting from gluing lead weights with epoxy tightly fitted in an old Terrier plastic boiler; I now prefer something less rigid!

I would not recommend a conversion to P4. There is no vertical movement in the axles; effectively this is a rigid chassis. Moreover I would be scared of the clearance needed in the front splasher. I guess one could fit a Branchlines chassis but the lightweight body and resulting lack of tractive weight is likely to be a problem.

[Peter HillParticipant]

Hi,
I have looked at this, but not tried it yet!
Colin (Alan Gibson) do a terrier conversion pack for the old Dapol/Hornby model, (cat number 4800/12), which has 2.5 mm axles, so the plan is to open out the brass bearings to 2.5, and try that.

I would love to know how you opened out the splashers in the footplate, this being what has put me off doing it.

I reiterate, I have not tried the above yet, but measuring it, I can see no reason why the re wheeling bit will not work.

Pete

[John CutlerParticipant]

Pete

Opening out the splashers was slow work using needle files.
Using a power tool struck me as potentially too uncontrollable.
And you need to be extra careful at the front; I still took a bit too much off!

My advice is to plan on minimum sideplay on the front wheels.
Then file, continuously measuring to that minimum clearance.

I warn you that I am not particularly happy with my result.
The slow-running performance is not good.
Maybe you will get better running using the Hornby brass bearings reamed out rather than running in mazak;
I missed that conversion option!

Good Luck!

[John CutlerParticipant]

An update.

I was not at all happy with the slow-speed running of the converted Terrier. So I bit the bullet and followed Pete Hill’s advice to replace the wheels with 2.5mm axle versions from Alan Gibson and carefully ream out the Hornby brass bearings. The bearings protrude slightly from the frames so I remeasured the spacing washers needed and settled on 2x1mm for each of the rear (driven) wheels but only a 1mm and a 0.5mm washer for the others. I suspect you do not have to over-worry about this as the splasher clearances are so tight the wheels are not going to wander too much. One recommendation is not to glue the final gear into place. Its position on the driving axle is quite critical if you want to avoid unnecessary friction. So by relying on just abrasion of the axle to retain it, the gear can be (carefully!) slid along the axle a bit if you get the position slightly wrong at the first attempt.

I found that some of the splashers were tight to the wheels, especially near the ends of the splashers. So more careful filing was needed. I ended up using 3M Magic Tape to insulate the insides of the splashers (a bit fiddly to cut the shapes required but once you get one right you can use it as a template).

However the running was still a bit erratic. The Hornby coupling rods seemed to flop all over the place. I reduced this by inserting brass AG coupling rod insert bushes between the rods and the crankpin nuts. Thus restricted, the coupling rod (rivet) joint proceeded to foul the axle end once per revolution! So another bush was inserted behind the AG crankpin bearing on the centre axle and this gives adequate clearance. I did buy the Alan Gibson coupling rods as substitutes but they are very chunky compared to the Hornby ones and need some careful riveting work to replicate the Hornby joints. I do wonder whether the jointed rods are overengineered considering the middle axle is not sprung (or compensated). I persevered with the original Hornby rods.

I discovered the rear axle crankpin nut would occasionally and erratically (caused by the rods flailing about?) clout the cab steps. So the rears of the steps were filed back slightly at 45˚ for extra clearance. Likewise I found I needed to carefully file away the rears of the brake shoes, again at 45˚, to get free running. For some reason this was more of a problem with the flanges of the rear drivers.

I realised the replacement phosphor-bronze wire pick-ups are a bit visible but they can be blackened with a Sharpie permanent marker to reduce the metallic glare. I found that pickup from the centre wheels is erratic or negligible because they are ever so slightly raised (by 0.1mm?); I think this is an old trick from the 1950s to try and stop the loco rocking on this axle (or is it?). I do wish Hornby had sprung this centre axle (why did they bother with jointed rods? Did they plan for a sprung axle and change their minds?).

I now have an EM Terrier capable of slow speed comparable to the Hornby M7. Unfortunately it is not as good a steady crawler as my Bachmann pannier.

[Paul MossParticipant]

This was very useful, thanks for posting.

I’ve recently started in EM Gauge and also purchased the newly tooled Hornby Terrier with the intention of doing an EM Gauge conversion (I’m modelling the IoW in the later 1930’s, so not a lot of options in terms of locos – I’ll probably settle on a couple of Terriers and a couple of O2s!).

Do you have any pictures of the conversion to share?

Seeing some of the challenges, I wondered if it would be viable to scratch build a new chassis instead of converting the Hornby one?

Regards

Paul

[John CutlerParticipant]

Sorry I did not take any photos of this conversion.
I did not consider i would end up describing it!

If you are considering a different chassis to the Hornby one, I would recommend using the Branchlines etched nickel-silver chassis as a basis.
I have built one of these (many years ago for the old Hornby body) and it is fairly detailed without being over-complex.
I have considered using this as I have one in store.
The problem is the lack of weight.
The new Hornby body is lightweight.
So you need to at least replicate the cast metal weight of the Hornby chassis and if possible add to it.
This requires careful planning of where and how to add weight to the etched chassis; I think I will pass on that!
You also have to make the underside of the boiler and ensure it acts as a cradle for the motor.

The Rails of Sheffield Terrier specification shows a sprung central axle.
I may be tempted to try converting one………

Good Luck!

[Paul MossParticipant]

@John Cutler said:
Sorry I did not take any photos of this conversion.
I did not consider i would end up describing it!

If you are considering a different chassis to the Hornby one, I would recommend using the Branchlines etched nickel-silver chassis as a basis.
I have built one of these (many years ago for the old Hornby body) and it is fairly detailed without being over-complex.
I have considered using this as I have one in store.
The problem is the lack of weight.
The new Hornby body is lightweight.
So you need to at least replicate the cast metal weight of the Hornby chassis and if possible add to it.
This requires careful planning of where and how to add weight to the etched chassis; I think I will pass on that!
You also have to make the underside of the boiler and ensure it acts as a cradle for the motor.

The Rails of Sheffield Terrier specification shows a sprung central axle.
I may be tempted to try converting one………

Good Luck!  

Great, that’s useful information, very much appreciated John

[John CutlerParticipant]

An update.

I am still not happy with the slow-running performance of the Terrier.
It tends to stutter at certain places in the yard .
After exhaustive tests with other locos I found this was unique to the Terrier.
The cause seems to be my awful uneven trackwork.
Not helped by being laid on camping mat (as advised by the illustrious ex-president of a rival society!).
I think that often only 3 wheels are in contact with the track and picking up current due to the bumps and the lack of any slop (or springing or compensation) in the axles.

I tried filing the keeper plate to try to allow the centre axle to fall slightly (it is raised above the other two).
This seems to have failed; I suspect the mazak holding the bearings needs to be slightly filed away too but this scares me.
Has anyone managed to do this?

I guess another possibility is to introduce vertical slop on all the wheels.

Otherwise the Terrier is going to end up being restricted to the main line.
A Branchlines chassis (already built) allied to girt great lumps of lead is being contemplated.

My recommendation is not to bet on good pickup and slow running unless the track concerned is perfectly flat.
The reality is that this was not the case for many of the yards worked by Terriers in their later years!

I was thinking about acquiring a new Rails/Dapol Terrier with sprung centre axle but this has had a lot of bad reviews due to poor quality control. Has anyone tried to convert one of those?

[Paul WillisParticipant]

@John Cutler said:
An update.

I am still not happy with the slow-running performance of the Terrier.
It tends to stutter at certain places in the yard .
I think that often only 3 wheels are in contact with the track and picking up current due to the bumps and the lack of any slop (or springing or compensation) in the axles.

I tried filing the keeper plate to try to allow the centre axle to fall slightly (it is raised above the other two).
This seems to have failed; I suspect the mazak holding the bearings needs to be slightly filed away too but this scares me.
Has anyone managed to do this?

I guess another possibility is to introduce vertical slop on all the wheels.

Bear in mind that without some form of springing or compensation, “slop” just generally results in the body settling in the lowest position and you have a de factor rigid chassis again.

Yes, a bit of slop can help on a centre axle, but you really need to be able to hold the axle at “mid-point” in some way so it can move up and down. An axle being able to drop only may be of use if you have a pronounced dip over a short (sub-wheelbase) length, but the improvement is marginal.

What problems have you identified in the track? A compressible substrate can cause issues – I know, my test-track sits on Exactoscale expanded foam, so should have vulnerabilities in the same way. But the real problem might be a vertical kink at a rail joint, or similar. No matter what it is laid on, an unbroken length of bullhead or flatbottom rail should have a dead straight flat top. Unless the baseboard has blown over in a carpark and the kerbstone has put a vertical kink in the rails across all running lines – DAMHIK!

I’m interested to hear more to help diagnose this. Would a picture of the troublesome track be possible?

Cheers
Paul

[John CutlerParticipant]

Thanks Paul.

I will not detract from this thread by showing my awful trackwork (but photos do not seem to be welcome anyway). I am tempted to rip up the yard and relay it, on solid styrofoam, probably using the new turnout kits from British Finescale.

I suspect part of the problem may be with pickups. I have managed to break 2 lots of the incredibly delicate Hornby pickups (a known problem) so gave up and installed long phosphor-bronze wires bearing on the backs of the wheels (overlapping the flanges). (note I could not upload a photo despite it being only 464Kb). Maybe I should replace the long lengths with coiled springs?

The split-axle and sprung Branchlines chassis (already built for an old model Hornby Terrier!) increasingly appeals but requires a lot of planning and brainpower to get a hefty weight on board.

Has anyone else converted a Hornby or Rails Terrier to EM successfully?

[John CutlerParticipant]

I decided to look at fitting the Branchlines chassis to the Hornby Terrier.
It looks as if at least 1mm of the frame tops will have to be filed off or the loco will sit too high.
That will seriously compromise the strength of the Branchline frames; on my previous build I found it wise to strengthen the the frames with bullhead rail along the top.
So probably not feasible.

[Author]

Posts