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Rhb Simon

A question to EM & P4 modellers about tackling slidebar & crankpin issues with comet cylinders.

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I've recently built a comet fowler 2-6-4 tank in EM & I've had to angle the slidebars outwards to get clearance for the crankpin. 

 

The clearance was very tight, I did use markits wheels admittedly but the slidebars would have needed angling out if I had used gibson as well.

 

How do you P4 lads tackle the cylinders & slidebars etc to get a working clearance as it must be very close when your working with walscharts etc. It might be something I'm missing which could be helpful on my next valve gear build ( pdk mucky duck )

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I don't suppose it will breach any commercial confidences now all these years later, but here are two sketches showing the agreement for the 2003 rejigging of the Comet GWR 2-cylinder case I was asked to undertake and a sketch for the outside-valvegear LMS case, where the final details of the green zone (for valve rod etc) were left to Jeff Ayers being advised at the time by John Brighton and John ??? (can't remember surname, but a prominent loco builder for Slattocks Juntion) because there wasn't quite time at the special MMRS meeting called to resolve the issue. But the green zone details were filled in later.

 

The LMS redraw was welcomed by most, but Dave Holt hated it!

 

 

comet-GWR-2cyl.gif.fd1bfb46b401a2720e8c876db99ba5bd.gif

 

 

comet-clear1.gif.e713dc6c9d92a452413208fefccb51d4.gif

 

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Markits wheels are actually overscale width in EM so this sort of problem is inevitable. Gibson wheels aren't but remember that P4 wheels are thinner - in practice there isn't much difference between EM and P4 in this respect. Make sure the leading coupling rod end and crankpin fastener are as thin as possible (or at least as thin as they should be) before fitting the slidebars. Many locos had recessed crankpin fasteners here for this reason, including this one. In many locos it's less of a problem because the coupling rod end and crosshead never coincide but in the Fowler 2-6-4T they are just about bang on (literally sometimes).

Always check that the cylinders are the correct distance apart, 6'8" in this case, many kit designers don't know or don't bother to check this dimension. I haven't built one of these Comet frames but very often the slidebars are much thinner than they should be which gives a bit more room but equally often the rods and crossheads are far too thick which negates this. In really desperate circumstances I will leave off the back of crosshead and fit a small thin vertical bar at the leading end of it, away from the coupling rod, to keep it on the slidebar. Clearances on full size locos can be vanishingly small, looking at the preserved Highland Jones Goods in Glasgow I couldn't get a finger between the crosshead and the coupling rod, divide this by 76.2 and you've nearly got an interference fit.

I do always like to get the cylinders at the correct spacing and always have slidebars and con rod parallel to the frames.

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A small I have been building a Martin Finney V2 in P4 along with recently converting a em 45xx to P4. The solutions I came up with for both was to use ultrascale crankpins with the recessed crankpins nuts. These have resolved my issue with the conversion and also the. V2's actual clearances definitely Xrated and lubrication is required! However the real thing really has no clearance either so I can understand why we have trouble when trying to build models of them! 

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Posted (edited)

There has always been an issue with clearances in EM, P4 and S4. This how I get round it with a leading partially or fully recessed crankpin. This is on a Dave Bradwell A1 frame set in P4. The rods are newly fitted Brassmasters replacement rods and are a little more 'beefy' than the originals which I replaced after a some wheelsip on one axle. Edit. I did forget to mention that there is absolutely NO sideplay on the leading axle and virtually none on the two trailing ones. This model can briefly be seen in motion on the 'rollers' on Youtube.   Regards. HL.

 

DSCN0588 (2018_10_24 10_38_18 UTC)-crop.JPG

Edited by harry lamb
Additional info regarding sideplay.

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Harry are those ultrascale crankpins? My next build I'm going to use gibson wheels as they are more to scale. I was thinking of using ultrascale crankpins as they do a recessed one for the leading axle which will make life easier.

 

Regards

 

Simon

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I should have added - zero sideplay on the axle behind the slidebars is very important. I don't expect to get a nut of any sort on the outside here, mine are fastened up permanently and the daft loose bush crankpin systems make the job even more difficult. Don't use them, a crankpin is a plain steel bar sticking out of the wheel, full size crankpin bushes are pressed into the rods, for our purposes the bushes need not exist. I use Romford crankpins screwed into Gibson wheels, flat backed coupling rods since the shape of the crankpin spaces the rods off the wheel boss. Fastener is a slice of 1mm I.D. tube soldered on or recessed and soldered if necessary.

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A trick I picked up while building High Level kits came from the instructions. Assuming that the coupling rods are laminated, ,remove the bearing from the top layer and go with a half thickness there. Reduce the size of the brass bearing by half as well and you have more room to play with. Given the location, the difference in thickness is only noticeable from very close range.

 

HTH,

 

Cheers,

 

David

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Posted (edited)

Good afternoon gents, 2 points here.  First, the Gibson wheel being more accurate than the Ultrascale 6' 8" Doncaster wheel? I would doubt that very much. Indeed No, not at all. I am still using some of Brian Rogers Ultrascale wheels and the later ones supplied by David Rogers and quality has been maintained whilst also sticking to the correct 26" crank throw. When you build Finney and Bradwell kits these things matter! However, the most accurate of these 4mm. wheels was the Bernard Weller/ Len Newman series of Doncaster wheels that emerged a few years ago but used a rather convoluted tapered axle system that appeared to put people off. I managed OK and so did others but they were not everybody's cup of tea. In the end you get what you pay for. But, I still occasionally use AGW wheels and they are fine. But nowadays to make things easier for myself I indulge myself in Ian Penbirths sprung diesel bogies in BR steam era infernal combustion jobs and they mostly run on Ultrascales  and some on Gibsons. I have attached a couple of shots of the Weller/Newman wheels for comparison. Regards. HL.

20140505_02_01_(2018_10_24_10_38_18_UTC).JPG

IMG_1740_(2018_10_24_10_38_18_UTC).JPG

Edited by harry lamb
Duplication.
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Hello again gents, This crank axle is made up from a faulty pair of Mr. Newmans and Wellers Exactoscale cast offs. There had been problems with the first batch I purchased and they were replaced without question. Consequently the kind gentlemen allowed me to keep the faulty ones to play with so I made 3 sets of dummy crank axles out of small brass tube and N/S offcuts. Crank settings are guesswork. Cheers. HL.

wheel1done (2018_10_24 10_38_18 UTC).JPG

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Sorry to post my random thoughts on this thread but i really like the look of P4. I am starting to scratch build platforms etc in 00 and the out of scale gauge track is really noticeable to me now, i think one day i will have to give P4 a go, looks like a lot of hard work.

Sorry to interrupt.

Paul.

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Good evening Paul. What you see in that picture is only track built to 18.83mm. gauge and a cosmetic set of wheels plus an axle. It was my old 'test track and shunting plank'. P4 in itself is an overall standard of the model making in that scale and you are not looking at part of a trainset built to P4 standards. Only the track gauge itself and the check gauges are spot on. The P4/S4 concept as a whole is much more than just wheels and rails. I build, or rebuild these 'planks' every 2-4 years. Depending what I want to do next. The wheel in the picture is standing on a BH code 75 crossing which has double slips on each entry/exit. To the wheels immediate left the double slip is built from code 55 F/B rail. Rail ideal for light industrial use. Other points and slips are built from code 83 and 75 F/B. Plus a couple from code 60 F/B and code 83 F/B. Rail is a mixture of N/s, steel and P/B. All stock that runs on it does not fall off, and does so on track intentionally built to trip it up as all are sprung or compensated and the track is not level.  I do not do any ballasting, scenics or buildings. The bottom line is I enjoy mucking about with what I've got and continuously altering and changing things. However, if I was you, EM would make more sense. If I had done that in the first place I might have had a nice little trainset by now but what fun I would have missed!!  Regards,HL.    

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The P4 wheel and track standards are a bit tricky, as you can no doubt tell from this thread, however worth the effort.  From a scenic point of view P4 track looks really good even with no rolling stock present.  EM plain track can look just as good but is let down by excessive point blade and check rail gaps that are designed for OO wheels.  P4 wheels, especially for steam locos look very much the part with narrow treads and fine flanges.  From an operational aspect P4 gets rid of the annoying wheel drop often present in OO/HO and probably in EM as well.

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Posted (edited)

Sorry, can i ask just one question?

If i built some P4 / EM track could i alter a RTR loco such as a Bachmann 4f or 3f jinty?

I guess thats what you are dicussing on the thread,sorry if i am being a bit layman.

Paul.

 

Edit to add, is this what i have asked?

http://www.brassmasters.co.uk/4f_easichas.htm

Edited by down the sdjr
Answer my own question.

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3 hours ago, down the sdjr said:

Sorry, can i ask just one question?

If i built some P4 / EM track could i alter a RTR loco such as a Bachmann 4f or 3f jinty?

I guess thats what you are dicussing on the thread,sorry if i am being a bit layman.

Paul.

 

Edit to add, is this what i have asked?

http://www.brassmasters.co.uk/4f_easichas.htm

The answer is yes and there are a number of ways to do it. You can replace the chassis with Comet (recommended) or High Level (not recommended for a beginner) chassis kits or you can do a simpler conversation as per the EMGS Manual.

To get the EMGS Manual you'll have to join the society which is recommended too.

Cheers

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Don't forget that ready to lay EM track and pointwork is now available from the EMGS too!

 

Members only though!

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22 hours ago, harry lamb said:

 However, the most accurate of these 4mm. wheels was the Bernard Weller/ Len Newman series of Doncaster wheels that emerged a few years ago but used a rather convoluted tapered axle system that appeared to put people off.

I'm pretty sure that these wheels had nothing to do with Bernard Weller but were produced when Andrew Jukes ran Exactoscale and were intended for Andrews ECML layout hence the concentration on LNER wheels.

Rgds

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Posted (edited)
5 hours ago, down the sdjr said:

Sorry, can i ask just one question?

If i built some P4 / EM track could i alter a RTR loco such as a Bachmann 4f or 3f jinty?

I guess thats what you are dicussing on the thread,sorry if i am being a bit layman.

Paul.

 

Edit to add, is this what i have asked?

http://www.brassmasters.co.uk/4f_easichas.htm

Paul,

The most straightforward way to dabble with P4 or EM is buy drop in wheelsets from Ultrascale https://www.ultrascale.uk/eshop/products/view/CAT007/307

Or Gibson .  Gibson's are cheaper but require mounting on the axles and quartering (I believe)

I bought a brass P4 set for a Bachmann 57xx Pannier and it runs well.  They come with crank pins enabling you to utilise the Bachmann coupling rods.  I had to fit new brake gear.

The wheelsets seem expensive but not when compared to a new chassis, motor, gearbox and wheels.....

 

Edited by Jeff Smith
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Posted (edited)

 

23 hours ago, down the sdjr said:

Sorry to post my random thoughts on this thread but i really like the look of P4. I am starting to scratch build platforms etc in 00 and the out of scale gauge track is really noticeable to me now, i think one day i will have to give P4 a go, looks like a lot of hard work.

Sorry to interrupt.

Paul.

 

The pros and cons of P4 are probably for another topic, but suffice to say I went P4 in about early 1988 and as I seem to have got it to work successfully (largely using RTR conversions) I've never regretted it.  The only drawback is bringing home a new RTR 00 loco (eg Hornby or Bachmann) and not being able to give it a good run right away....

But to get back on topic - I can't comment on Comet cylinders, but I have done 3 successful P4 conversions of big outside cylinder RTR locos: a Bachmann WD 2-8-0, a Bachmann BR Standard 4MT 2-6-4T and a Hornby Britannia.  The WD was inspired by the Dave Booth articles in ScaleFour News 148-150 and the 4MTT by the Tim Shackleton articles in MRJ 133 & 134, while the Brit conversion I devised myself using the experience gained with the other 2.  They are the most relevant here as the leading drivers are right behind the crossheads: as Michael Edge says, you need zero sideplay on the leading axles.  I used Gibson wheels and crankpins/bushes/nuts: it's been quite a while since I did these conversions but it doesn't look like I angled out the slide-bars or widened the cylinders, though I did use reversed nuts on the leading axle of the WD and may have filed down the nuts on the 4MTT a bit.... 

 

HTH

 

Alasdair

80113 LH crankpin.jpg

Edited by AJCT
Insert pic
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1 hour ago, Grovenor said:

I'm pretty sure that these wheels had nothing to do with Bernard Weller but were produced when Andrew Jukes ran Exactoscale and were intended for Andrews ECML layout hence the concentration on LNER wheels.

Rgds

The C&W wheels certainly appeared under Bernard Weller's ownership, and the loco wheels were announced - I recall lobbying Bernard for a tyre face width appropriate for LNER practice. Though it was certainly Andrew's drive that ensured a suite of LNER wheels eventually appeared. I do hope they re-appear before too long.

 

The Nim.

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Posted (edited)

Good evening gents.  I have this picture of the said A1 after a trail trip round the 'plank' happily weaving through a number of reverse curves in forward and reverse with Rizla (blue) clearance on the lead C/P and little end con rod when the loco suddenly stopped in it's tracks! I had taken a couple of stills of it's progress, some years ago now, and with the enlargement you can clearly see why! It's picked up a dog end of pick up wire! This is not off the loco or tender as I haven't used wire pick-ups on tender loco's and bogie diesels for years and the loco had not been fully restored. I do get some shunter repairs now and again but all my own small stuff is split axles. However, the reason I posted this enlargement is that it also gives a clearer view of the leading crankpin partially behind the con rod as it came to stand. And it does work. However, if I would wish to build an A2/1/2/3 or a K1/3 or any outside cyl. loco where the c/p is behind the slidebars in EM/P4 then Mike Edges system would seriously need to be considered and it's more than likely that would be the road I would take. Regards. HL. ps. I'm usually on a railway station on a Friday and Sunday nights (retired 6 years).........supping!   

DSCN1038 (2018_10_24 10_38_18 UTC).JPG

Edited by harry lamb
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