Comet V2 Chassis kit

[Steve Taylor]

Having, via a certain well known internet market-place, acquired one of these some weeks ago, I finally got chance to have a proper look at my purchase yesterday. A phone call to Gibson enterprises is in the offing for wheelsets and a motor and gearbox drivetrain will need to be decided upon and also acquired. Now the decisions!

 

The kit seems to be designed primarily for a rigid 00 application. I want to produce a p4 piece (i know pervert and weirdo etc). Now the frames are marked for hornblocks but the previous owner has got as far as soldering in bearings for the front and rear driving axles and partly fitting two frame spacers (the wrong way round). Lesson number one: just how much heat is required to break a solder joint to remove the spacers. Now i could go with this, respace it and produce a rigid model, I could cut out for hornblocks and springs, or I could produce two V2's, the first rigid and the second sprung as a learning excercise. I have spare bodies for engine and tender so though the latter is pricey in extra parts its an option since i would need a tatty v2 and an ex-works one in the long term. I do own up to the keep it simple and get something produced instant gratification of the rigid option but what does the learned panel consider a good route and does anyone have any experiences of these kits they'd care to share?

 

Also - drivetrain: any reccomedndations or go with Comet's reccomended mashima and loco mounted motor combo? Yes I've been reading Tim Shackleton's book so there are probably far too many ideas wizzing around for a novice but hey I got to start somewhere.

 

Cheers All

Steve

[Pinkmouse]

Strip it down and start again from scratch. The spacers may well be the wrong size for P4 anyway, so you'll need to replace them, and taking out the bearings isn't that much extra work. I use a plumber's blowtorch for dismantling as it gets lots of heat into the joint quickly, and saves damage from trying to pry bits off with the limited amount of melting a standard iron achieves. If you give the parts a quick wipe over with a fibreglass brush whilst the solder is still molten you can get rid of most of it then as well, saving time in cleaning up later.

[Horsetan]

....Lesson number one: just how much heat is required to break a solder joint to remove the spacers.

 

Not a huge amount. You could use the blowtorch method suggested above. I've managed to dismantle frames when I've made erecting errors just by using my 25w Antex to melt the joins, plus a screwdriver bit to prise the parts away from each other.

 

Now i could go with this, respace it and produce a rigid model,

 

Rigid not recommended for P4/S4.

 

I could cut out for hornblocks and springs,

 

Pretty much a default requirement in P4/S4.

 

....or I could produce two V2's, the first rigid and the second sprung as a learning exercise.

 

I'd work on just the one. In fact, I have had parts for one for years (see below). Just haven't got around to it.

 

.....what does the learned panel consider a good route and does anyone have any experiences of these kits they'd care to share?

 

My box contains: old Bachmann V2 body, duly stripped down. Branchlines chassis fret + castings. Comet V2 valve gear fret ('cos I thought the Branchlines effort was a bit half-hearted). Alan Gibson wheelsets for S4, plus pony wheels from Ultrascale.

 

Tender undecided - I'll probably end up building one from the Dave Bradwell kit, since this is designed for S4 anyway and includes leaf sprung suspension.

 

Also - drivetrain: any recommendations or go with Comet's recommended Mashima and loco mounted motor combo? Yes I've been reading Tim Shackleton's book so there are probably far too many ideas whizzing around for a novice but hey I got to start somewhere.

 

For a quiet life, use Comet's recommendation. You may prefer a geartrain made by High Level Models - they've got at least one which can fit in almost anything.

 

If, like me, you were nauseatingly lucky / far-sighted, you'll have a drawer full of Portescap RG4 coreless motor / gearbox combos in the three standard sizes which you snapped up in the 1990s/early 2000s, and from which you can pick and choose. They have bevel-and-spur geartrains which I love, and pretty much go straight in. Saves you having to build a geartrain and fiddle about with gear meshing, etc. Job done.

[Barry Ten]

One tip for unsoldering frames is to spring a pair of wooden clothes pegs between them before you apply the iron. Once the solder starts to give, the frames should pop apart.

[Steve Taylor]

cheers all and stand by for further dumb questions as this slowly proceeds.

 

Ok, I've gone for the single version at this stage and will probably use Comet's recomended choice for motor/g-box. I know everyone seems to rave about High-level but i wouldn't know where to begin in selecting one. I know the biggest motor possible makes sense so if anyone thinks that they know of a big motor gearbox choice that is proven in terms of power, reliability and longevity, well I'm open to suggestion. Also let me know your thoughts on where to locate and how. Told you I was knew to this - oh and am a bit bamboozled by all the books.

 

"OOOH 'eck, look out yer window Mr H.Tan, there's Shergar and Red Rum waltzing accross your lawn, unless i'm very much mistaken" - /me helps me'sen to a spare from the strategic Portescap reserve. "Oh, wasn't there, sorry, but I am awaiting new contact lenses"

 

At the moment I'll probably plumb for just sprung hornblocks, compensation may be a bit exotic for my lack of skills at this stage.

 

As far as the tender goes, there is a mainline chassis kit with this lot, so I'll start with that and see how i go - possibly look at springing it a-la Mr Bedford's wagon system, unless he does a suitable underframe. Though if the loco build goes swimmingly i might treat it and myself to a Bradwell.

 

All dismantled btw the way now, just the job on a really hot day, nearly as much fun as dismantling a relay room was yesterday!

 

Cheers all.

[Horsetan]

....I know the biggest motor possible makes sense so if anyone thinks that they know of a big motor gearbox choice that is proven in terms of power, reliability and longevity, well I'm open to suggestion. Also let me know your thoughts on where to locate and how....

 

If you are now going for the Comet option, download their overlay here - this contains some of the possible combinations which you can position beside the body / chassis / a reliable scale drawing to give you an idea of where you can position things.

 

You do have the advantage of a wide firebox into which either the gearbox or the motor barrel should fit with some room to spare - anything up to 16mm diameter. I would, at first instance, try to drive the rear driving axle.

[Steve Taylor]

Cheers for getting back to me, Do you consider the Isinglass drawing up to the job? I'd forgotten that I had that so ta for the reminder.

Assuming that the motor/g-box diag is to scale is it available as a jpg for sections to be used as overlays on the GA drawing in photoshop so I can sort of try for size? Failing that, I'll scavenge round work for some acetate to print on.

 

All advice welcomed - I've got a bit of momentum going to get on with things at the moment.

Cheers

Steve

[Horsetan]

Cheers for getting back to me, Do you consider the Isinglass drawing up to the job? I'd forgotten that I had that so ta for the reminder.

Assuming that the motor/g-box diag is to scale is it available as a jpg for sections to be used as overlays on the GA drawing in photoshop so I can sort of try for size? Failing that, I'll scavenge round work for some acetate to print on.

 

The idea is that you print out the Comet diagram sheet directly and use it as a full-size overlay on your 4mm scale drawing.

 

The Isinglass drawing is an excellent one, as is virtually every drawing from that source.

[Steve Taylor]

Which I've just done roughly - though my one remaining lightbox is hidden in the office at work. A rough lining up would suggest that a 1628 is possible with at least one flywheel. though then having checked the instructions it seems a 1628 was the recommendation in the first place. I really must stop trying to re-invent the wheel. Thanks again.

 

Ps thanks Barry-Ten for the peg idea - most useful.

[34theletterbetweenB&D]

... I know the biggest motor possible makes sense so if anyone thinks that they know of a big motor gearbox choice that is proven in terms of power, reliability and longevity, well I'm open to suggestion. Also let me know your thoughts on where to locate and how. ...

What Mashima used to term a 14/26 (or the larger cans) with anything from 30:1 to 60:1 reduction will do the job; 30:1 if you intend belting it along, 60:1 for slow speed movement. Drive the centre axle with the motor to rear of the gearbox. That will leave plenty of spcae fore and aft to balance the loco with any additional weight it requires. Support the motor on the gearbox at the front end, and on a bearer across the chassis at the rear end of the motor. A small rubber band of a length that gives light tension looped around the bearer and over the motor can will restrain the motor while allowing it to float with the axle.

[Horsetan]

^^

I've often wondered - just for the sheer hell of it - whether a variable gearbox could fit between the frames, so that you're not limited to just the one ratio. A sort of DAF Variomatic for model locomotives.

 

.... I really must stop trying to re-invent the wheel....

 

Reinvention might be a bit much, but even a wheel can be "improved" where occasion demands it!

[the penguin of doom]

The Isinglass drawing is an excellent one, as is virtually every drawing from that source.

 

Having used the Issinglass drawings for a few of my projects, I'd recommend them.

 

Looking forward to seeing how the build progresses. Up to now, I've shyed away from chassis construction, so if there was an emoticon for taking my hat off to you, I'd use it.......

 

Nope, that one'll have to do.....

 

Cheers.

 

Sean.

[Horsetan]

....if there was an emoticon for taking my hat off to you, I'd use it.......

 

Nope, that one'll have to do.....

 

[Lambton58]

If you are now going for the Comet option, download their overlay here - this contains some of the possible combinations which you can position beside the body / chassis / a reliable scale drawing to give you an idea of where you can position things.

Highlevel have a similar gearbox planner on their website. I printed it onto clear acetate so I could overlay it onto a plan of the loco

[Steve Taylor]

ta for the high level link - i'm intrigued to try something different to compare with the comet box going into the j72 currently underway.. Going by experiences with that so far, I quite enjoy chassis construction. It seems logical though at times a little fiddly. Steady away, fail to prepare, prepare to fail, measure twice, cut once etcetc.

 

Sean if its any consolation..... bodywork terrifies me at this stage, so I've been reading your stuff with interest. At the moment i have 3 loco bodies and two tenders to go at. Obvious thoughts are the moulding lines, handrails and the pipe work along the driver's side of the boiler as well as cab glazing. Anyone else any thoughts? Reading Yeadon, I'm thinking an ex-Darlington works finish, apparently running in turns went through Broomielaw at times so I can just about justify this. The shell is for a v2 with separate cylinders, so i need to sit with the book and work out which one will fit my requirements.

 

Looking at the comet frames they are their older style frames without the spring keepers etched in. Now i could possibly craft something into the metal work when i remove the metal for the hornblocks, but if someone can recomend a hornblock set so i try something different that would be most welcome. I've a set of Gibson ones set aside for one of Arthur's J24s (itself set aside for when i feel confident enough to try boiler rolling!), But have looked at Exactoscale's website, and after having recovered from the shock of the wheelset prices am thinking their hornblocks might be worth a go. Any thoughts anyone?

As to

 

At this stage, while i suss out what to do and how, this must read a bit like modelling by committee, though as chairman and executive holder of the credit-card I hold the final veto I do promise to give all suggestions and reasons careful consideration.

 

Mr H-Tan - re your portescap stockpile. They are a name I'd heard of years ago but have no experience of. Perhaps for us younger persons/newcomers/novices/ignoramae etc you could tell us something of them - if for no other reason that I'm curious why a secondhand motor can command £25 on ebay.

 

Cheers All

Steve

[Adam]

If you can get one for £25 you'll be doing very well!

 

Basically, they're a coreless motor attached to a bespoke gear box which drives through bevel gears rather than a worm (something to do with coreless motors having difficulty with this type of mechanical load - Bertiedog is your man for this kind of detail). They produce a very smooth, powerful and largely hassle free drivetrain with a low current draw and were regarded as the Rolls Royce of model transmissions when they were first introduced. They're still very good if you can get them though personally my default option is a High Level 'box at one end of a Mashima with a flywheel on the other. You can get carried away with this kind of thing of course, but the majority of modern transmission bits seem to work well enough and are rather quieter than the Sharman and Romford gears that used to be the staples

 

As a kid, the principal benefit of a Portescap (dad had one in an 03 - this now has a High Level chassis: not a fault of the motor, it's that shunters shouldn't be able to do 50mph...) was being able to push the loco along!

 

Adam

[Horsetan]

^^

What he said.

 

You'll be lucky if you can snap one up on eBay for £25. £75 seems to be commonplace nowadays. I've never paid more than £40 for any of mine, but that was in the days when they were plentiful and still in production.

 

I'm a big big fan of bevel gears, mainly because the rolling resistance is a bit lower, and wheelsets don't get locked-up when the power's turned off.

[RedgateModels]

No-one's mentioned DJH gearboxes yet, very smooth and quiet in operation due to the nylon worm used.

[Horsetan]

No-one's mentioned DJH gearboxes yet, very smooth and quiet in operation due to the nylon worm used.

 

Not bevels, though, so I don't use them.

[craigwelsh]

I'd recommend High Level hornblocks if you want to try something different as well as their gearboxes which I found far better than the Comet.

 

The later Portescap gearboxes squeal like a pig and this certainly gives me a headache! I'd probably have eBay'ed any if i'd been in the hobby when you could buy them though..

[Horsetan]

.....The later Portescap gearboxes squeal like a pig .....

 

I've heard quite a lot about this - generally seems to affect some of the ones that were packed in the later blue card surrounds and some that were simply bubble-wrapped inside the larger white boxes. Something to do with the moulds for the plastic gears starting to wear out?

 

Quite a while ago, I gave the ones that I have a spin under 9v battery power, and I couldn't detect a squeal on any of them - they all had their original red-tinted lubricant. Maybe I'm going deaf, or can't hear high-frequency sounds?

[Steve Taylor]

Craig, thanks for making me look round the high-level site properly. Methinks I shall try them for the motor and gearboxes - very competitive pricing, and i f I get my maths right a nice set of ratios. Being able to crawl through the platform at a scale walking pace or less would be most usefull.

I'm still trying to work out the hornblocks. How they go together seems very simple but how to spring them seems to require me to have a bit of a think. I might have a set for my other J72 to try compensation on before the V2. I'm certainly getting some in to have a look at though.

Thanks for the portescap explanation chaps - out of interest, what happened to them as they seem to be a popular benchmark for some people why are they no longer in production?

[Guest Max Stafford]

Craig. Take your time to build the High Level unit. Couple it to a large Mashima can and you will have a drive the equal of the finest. You won't be sorry. I used a Mashima/High Level combination in my J27 and it's the best drive unit set-up it's ever been my pleasure to use!

 

Dave.

[Horsetan]

....Thanks for the portescap explanation chaps - out of interest, what happened to them as they seem to be a popular benchmark for some people why are they no longer in production?

 

The Escap/Faulhaber coreless motor itself continues to be made, in a variety of sizes, but it was the gearbox which went out of production. There are any number of reasons for this - my memory of what happened is hazy now (mainly because of my fondness for alcohol), but I recall the following:

 

- The RG4 range initially began as a Kean-Portescap product (that's Kean, as in Kean-Maygib). All the geartrains came ready-lubricated.

 

- At some point, possibly as a result of takeovers, etc., the RG4 range (comprising the "M" large, "C" medium, and "1219" small) then appeared under the "escap" label. This remained the situation for a good number of years - well over a decade - hence the once-familiar red and later blue cards wrapped around those clear plastic boxes. The 1219 motor was actually labelled as a "minimotor" on the motor barrel, being a Faulhaber.

 

- Escap, in the UK at least, was then subsumed into the API Positran group, and the RG4 range now bore their label for a while. By this time, people were noticing that the lovely low-resistance geartrain was no longer quite as smooth as it used to be.

 

- It is probably in the last 5 years or so that the RG4 (or rather its gearbox) has ceased production. There is probably no commercial will to rejuvenate the mould tools for the bevel gears. You can still get the coreless motors by themselves, though.

 

Nowadays, if you want bevel gears, or rather their contrate-and-pinion equivalent, you have to get them from Ultrascale or Scalextric, and then design your own gearbox to house them....

 

There is a slightly more robust coreless motor range called Maxon, but that's another story.

[Earlswood Nob]

This is the general method I use for choosing motor gearbox combinations

 

HIGH LEVEL GEARBOX USE

 

30:1 Not used

40:1 Passenger & Mixed traffic eg LNER A4 & V2 & V1

54:1 Freight haulers eg LNER J21 & O4

60:1 Shunters/trip freight locos eg LNER J50 & N8

80:1 Pure shunters & banking locos eg LNER J72 & U1

108:1 Dock shunting & Hump shunting eg LNER Y7 & T1

 

One chooses the gearbox design by superstructure requirements.

These are the combinations that I have used, with Mashima motor in brackets.

 

A4 & V2 Use Highflier 40:1 (1628)

O4 Use Highflier 54:1 (1624)

J21 Use Roadrunner Plus 54:1 (1024)

J50 Use Loadhauler Plus 60:1 (1620)

N8 Use Loadhauler 60:1 (1620)

J72 Use Humpshunter 80:1 (1024)

U1 Use Loadhauler Plus 80:1 (1624)

Y7 Use Humpshunter 108:1 (1015)

T1 Use Loadhauler Plus 108:1 (1628)

 

Good luck with your project.

 

Earlswood Nob