Converting Heljan 00 railbus to P4

richard payne
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Converting Heljan 00 railbus to P4

Postby richard payne » Wed Feb 28, 2018 5:30 pm

Having recently converted to P4 and joined the society, I would like advice as to where I can source correctly profiled wheels to allow me to convert my Waggon & Maschinenbau Railbus in 00 to P4. This will be my first attempt at re-gauging a locomotive so I will probably need all the help I can muster.
Many thanks..... Richard.

richard payne
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Joined: Mon Aug 21, 2017 11:25 am

Re: Converting Heljan 00 railbus to P4

Postby richard payne » Wed Feb 28, 2018 6:21 pm

I've just looked through the message list and have found other posts on the same subject which I will follow up; but I would still appreciate any further comments/suggestions that may be relevant,

Thanks..... Richard.

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Paul Willis
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Re: Converting Heljan 00 railbus to P4

Postby Paul Willis » Fri Mar 02, 2018 6:45 am

richard payne wrote:Having recently converted to P4 and joined the society, I would like advice as to where I can source correctly profiled wheels to allow me to convert my Waggon & Maschinenbau Railbus in 00 to P4. This will be my first attempt at re-gauging a locomotive so I will probably need all the help I can muster.
Many thanks..... Richard.


Morning Richard,

Welcome to the Scalefour Society! I saw your recent questions on the GER Society email list about modelling in 4mm. Unfortunately I have real problems posting on the GERS group, so wasn't able to reply over there, although I saw that you have received some responses.

As you'll have found from our own Forum here, there have been some of past discussions of the Railbus. I believe that at least a couple of the members of my own CHEAG Area Group have converted these railbuses. I've asked on our email group for any hints or tips.

One of them also pointed me to a blog, showing how it came apart. The subject of the post was to convert the railbus to EM, but in all practical terms it will make no difference. You'll find it here from Bawdsey https://bawdsey.wordpress.com/2012/03/02/heljans-waggon-maschinenbau-railbus/

Having asked a couple of questions, I hope you have some answers. I'm afraid that the period you're modelling is some fifty years too modern for my interests of the GER around 1910, so as usual, I can be of no practical help ;-)

Cheers
Flymo
Beware of Trains - occasional modelling in progress!
www.5522models.co.uk

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PeteT
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Re: Converting Heljan 00 railbus to P4

Postby PeteT » Fri Mar 02, 2018 9:31 am

David Hawkins had one running on Great Bardfield at Portsmouth in November - an excellent job of it he had made too!

His contact details are available here : http://www.shmrc.org.uk/member-layouts/great-bardfield/, or possibly via this forum(?).

Jeremy Good
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Re: Converting Heljan 00 railbus to P4

Postby Jeremy Good » Fri Mar 02, 2018 10:55 am

Richard

I've got an AC Cars version of the Heljan Railbus in my "to convert" pile. I think it is mechanically the same as the W&M version, it certainly looks like it from the Bawdsley post, although the AC version seems to have its own issues as the side frames are closer together.

From my initial investigations it looks like it will take the Branchlines 12mm wheels relatively easily. I'll have a closer look at it over the weekend and try and take some photos to give you a step-by-step guide if that would help although I suspect the final step, attacking the side frames with a big file to get clearance, won't be necessary for you!

Jeremy

Jeremy Good
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Re: Converting Heljan 00 railbus to P4

Postby Jeremy Good » Fri Mar 02, 2018 7:49 pm

Having heeded the requests not to try and travel to the office due to the weather I've been working at home and have had a chance to look more closely at the Railbus conversion. Mine is now running quite nicely on its new P4 wheels and I will try to provide a step-by-step guide to the conversion. Looking at some of the photos elsewhere on the web it looks as though the W&M version may be a little different to the AC one and possibly a little easier to convert but I'll highlight what I this are the differences as we go along. I also need to thank Andrew Ullyot for providing some information on the conversion which helped me to understand how the model was put together.

The Railbus seems to be quite a complicated model to get into but, fortunately for the wheel swap, we don't need to try and get access to the interior, yet - that'll come when it gets a driver, a passenger or two and possibly a DCC decoder.

Let's start.

I've used Branchlines 12mm "Black Beetle" wheels for this conversion. I have largely standardised on these for new builds of coaching stock and DMU's as I find them to consistently run true, allow for adjustment of the back-to-back gauge easily and being solid metal make arranging pick-ups very simple. They come on a 2mm pin point axle and are supplied with either one or both wheel insulated from the axle, mine were both insulated which I thought would be useful especially as it is actually difficult to see the innards of this model and see if live axles would cause any difficulties with shorting. The wheel sets, shown below, were dismantled by removing one of the wheels from each axle. I used a GW Models gear puller but they will twist off if you provide a little force. The pinpoints on the axles were filed nearly flush with the face of the wheel and then they were put aside until I had dismantled the Heljan wheel sets.

IMG_1372.jpg
Branchlines wheels


The next view shows the underside of the model. The axles are retained by individual keeper plates secured by the 3 crosshead screws visible on each one. These were removed to release the axle and wheels with gear fitted. From the photos shown elsewhere this looks to be a slightly different design to the W&M version with extend brass bearings which take up most of the side-play in the axle and provide a bearing surface within the mazak casting that forms the main chassis block. I'll comment on the impact of the design difference later.

IMG_1373 copy.jpg
Underside of Heljan AC Railbus
IMG_1374.jpg
Keeper plate removed


The axles and wheels were removed. Before dismantling the wheels I measured the existing back-to-back (14.35 mm) and the distance from the inside face of the wheel to the corresponding side of the gear (4.25mm and 8.15mm) respectively to allow me to copy the offset of the drive gear. The existing wheels pulled off the axle releasing the bearings and giving access to the gearwheel which is a tight push fit on the axle. The gear was removed again using the gear puller although they could be carefully drifted off the axle if this tool isn't available.

IMG_1376 copy.jpg
Partly dismantled 00 wheel set
IMG_1379 copy.jpg
Fully dismantled wheel set


The new wheel sets were assembled. Taking the axle with one wheel in pace I added the longer bearing and then the gear. Having measured the position earlier on the 00 wheel set I could work out where this needed to be positioned. It could be done by eye but, for once I thought I'd try and be a little more scientific! I knew the back-to-back of the new wheel set would be 17.75mm (thats what my gauge measures) so I could calculate the difference by adding half the difference between the back-to-back measurements (i.e. half of 17.75 less 14.35mm = 1.7mm) to each of the wheel rear to gear measurements, this gave me distances of 9.85mm and 5.95mm. The gear was positioned accordingly, the second bearing fitted and finally the other wheel. This was then pushed onto the axle fully to give my standard back-to-back measurement. The other axle was also dealt with in the same way.

I think this is the main area where the W&M model differs. The bearings on the AC version are quite effective at limiting side-play on the wheels to about 0.75mm on each axle. These bearings are absent on the W&M version so, before fitting the gear and second wheel sufficient 2mm diameter washers to remove the side ply to ensure that the gear stays in mesh with the other gears and the wheels don't hit the inside of the chassis block casting/axlebox mouldings. These washers could be traditional metal washers although I often use a little dodge suggested by Alan Gibson of using cylindrical off-cuts of BIC Biro inners (the tube that carries the ink) which is conveniently a 2mm diameter tube, easy to cut and considerably cheaper than a set of etched/turned boss washers! Whichever way is adopted I feel that because of the long wheelbase of these vehicles a little side-play would be helpful - the 0.75 mm suggested earlier seems reasonable.

IMG_1375.jpg
Comparison of wheel sets
IMG_1380 copy.jpg
Competed P4 Wheelset


We should now have 2 completed axle units which may but probably don't fit between the axlebox mouldings on the chassis. On the AC version I had a 21.6mm gap between the axle boxes and wheel sets that measured 22.1mm across the face of the axles. I'll look at how I dealt with this in part two.

Jeremy

Jeremy Good
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Re: Converting Heljan 00 railbus to P4

Postby Jeremy Good » Fri Mar 02, 2018 8:46 pm

Part 2...

Having prepared the wheel sets, in an ideal world, we could just put them back into the chassis moulding, re-fit the keeper plate and go and play trains. Unfortunately with P4 models it is rarely that simple.

I knew from my earlier investigations that the wheels were not going to fit between the axle box mouldings. On the AC this is a single moulding providing the cosmetic under frame as well as the axle boxes. It is meant to be a friction fit with 6 lugs being pushed into holes in the mazak chassis block. The cosmetic underframe fittings need to be removed, carefully, first - they mostly pull out - and then I started at one end and slowly eased a screwdriver blade between the moulding and the chassis to release the lugs, there are two at each end and one on each side. Four of these came out easily but 2 were glued and required a little more force - they will need to be glued back now! Once the moulding was freed I measured the width of the moulding at each axle box and then set to with a large file to remove approx 0.7mm from the inside face of each, this extended the 21.6mm cleaner to 23mm giving me a little side play on my axles which were 22.1mm overall. These measurements aren't critical and can just as easily be gauged by sight.

From the photographs this is an area where the W&M differs and it looks as though the axle boxes are individual mouldings - they may provide sufficient clearance but I'm afraid I can't comment conclusively.

IMG_1384.jpg
Cosmetic underarm moulding - axle box before and after
IMG_1387 copy.jpg
Cosmetic under frame


Once all the axle box mouldings had been filed back I refitted the wheels and keeper plates. It was obvious that the wheels were touching the chassis block and wouldn't rotate. I then scraped away at the chassis block to create some clearance, initially with a craft knife but eventually with a dental burr in my mini-drill. The chassis block by each of the wheels needed some material moving as can be clearly seen from the photos - the cutouts are about 2mm wide and 1 mm deep - giving clearance for the wheels to rotate and re-instating the lost side play. While I was grinding this material away I held the pick up wires away from the drill and protected the gears from the mazak dust by plugging the axle holes with pieces of blu-tac. Once the grinding was finished I carefully cleaned the dust off the castings.

IMG_1388 copy.jpg
Chassis block - areas ground away to give clearance/pick ups


The pick up wires, which can just be seen in the photo above, were gently bent outwards so that they rubbed lightly on the back of the metal wheels, the axles refitted and keeper plates screwed back into place.

IMG_1389.jpg
Underframe with P4 wheel sets fitted


The Railcar was then track tested and runs as well as it did before I started the conversion. The cosmetic details on the underframe need to be re-instated and the brake mouldings (not fitted on the W&M) need to be adjusted to line up with the wheels. It is then the small matter of getting into the interior, painting that, fitting passengers and a crew and then it can take over the passenger service to Wheal Elizabeth Halt.

IMG_1390.jpg
W79978 at Wheal Elizabeth Halt


I hope that these notes/photos are some help to anyone embarking on this conversion. The AC version seems a little more involved than the earlier versions due to the additional underframe details but this is a relatively easy way to get a complete branch-line train up and running swiftly. The Railcars had a reasonably wide geographic spread during their service days, this one starting at Tetbury before going to Bodmin and then heading to Scotland, so although they were short-lived they do offer plenty of scope for layouts across the country.

If you'd like any more information on the conversion please ask, either here or via a PM.

Jeremy

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Paul Willis
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Re: Converting Heljan 00 railbus to P4

Postby Paul Willis » Sat Mar 03, 2018 7:41 am

Jeremy Good wrote:Part 2...

Having prepared the wheel sets, in an ideal world, we could just put them back into the chassis moulding, re-fit the keeper plate and go and play trains. Unfortunately with P4 models it is rarely that simple.
<snip>
I hope that these notes/photos are some help to anyone embarking on this conversion. The AC version seems a little more involved than the earlier versions due to the additional underframe details but this is a relatively easy way to get a complete branch-line train up and running swiftly. The Railcars had a reasonably wide geographic spread during their service days, this one starting at Tetbury before going to Bodmin and then heading to Scotland, so although they were short-lived they do offer plenty of scope for layouts across the country.

If you'd like any more information on the conversion please ask, either here or via a PM.


Jeremy,

I'd just like to say thank you, on behalf of everyone who may in future read this thread, for taking the time to post your pictures and experiences of this build.

It shows both the obvious (e.g. which screws to remove), and the tricks (e.g. to avoid shorting out), which will be so helpful. Much appreciated!

Cheers
Flymo
Beware of Trains - occasional modelling in progress!
www.5522models.co.uk

richard payne
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Joined: Mon Aug 21, 2017 11:25 am

Re: Converting Heljan 00 railbus to P4

Postby richard payne » Sat Mar 03, 2018 12:38 pm

I would also like to add my thanks to Jeremy for his comprehensive guidance, and also to Flymo and all other contributors, I now feel able to proceed with confidence. Just for the record, my W&M railbus was pre-owned and appears to be unaltered. It is very similar to the one illustrated by Jeremy in all aspects except for two areas - axles are held in position by three small washers either side of the nylon gear wheel, and the axle-box frames are all separate items and are easily removed. After re-gauging, it would appear that a light sanding on the back of the axle-box frames will be all that is required to clear the outside faces of the wheels. Once again a very big thank-you..... Richard (7075).

J Gleeson
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Re: Converting Heljan 00 railbus to P4

Postby J Gleeson » Mon Jan 13, 2020 7:45 am

Dear Mr Good,
Many thanks for taking the trouble to describe your railbus conversion. I will follow suit shortly.

Regards

J Gleeson


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