Chassis suspension/compensation

[adigill]

A quick question, do P4 locos always have to have suspension? Does anyone out there run their locos with rigid chassis and if so what are your thought's/finding's on using this method. Or is it that everyone always add's suspension of some sort?

[Will L]

While there is no doubt that various people have made rigid chassis work in P4, the accepted wisdom is that some form of chassis flexibility is desirable. But then many 00 gauge exhibition layout will employ loco suspension because of the improved loco performance.

Note that it is long rigid chassis, normally steam outline, loco's which need help most, bogie locos have a certain amount of flexibility and need less help. Many commercial chassis loco's do feature some flexibility. If you plan to build your own, then it is my view that it is actually more difficult to build a reliable rigid chassis than to fit compensation or springing. A slightly out of square rigid chassis isn't going to work on a P4 layout.

Will

[Tim V]

Depends what you mean by "rigid".

There are a lot of RTR conversions successfully running around, do you class those as "rigid"?

If you mean brass chassis with close tolerance brass bearings, so the axles have no slop whatsoever, then you would have to be very lucky to keep such a machine on the road. Plus the main reason for compensation/springing/slop is for reliable pickup, so a "rigid" machine like this would not be a reliable one.

[Tor Giffard]

Aft'noon A,

With due credit to Dapol I took the prototype Ultrascale P4 converted Western and class 22 to run on Dick Petter's 'Knutsford East' recently and each ran flawlessly despite super-elevated trackwork and the occasional dip in the track. Neither had suspension and apart from checking the 'back to backs' no other prep work was done.

Dave

[adigill]

Thank's for adding your comments, I guess the reason for putting up this post is that I now have 15 loco kits to build and the thought of building all those chassis with compensating beams or CSB, setting up of horn guide's etc seems like it'll take forever (life's to short!!) so I wondered if fixed bearing's on my Holiday hobbies jig would be an easy option but it does'nt sound like it's a good idea.

[Tim V]

You have a useful jig, so I think you'll find it doesn't take that long. If you have that many, the best way to do it is as a batch, that way you can quickly refine your technique. The first one will take a long time, but by the time you've done few, you'll be flying through!

[Will L]

Tim's right, and remembering what he pointed out earlier,that rigid etch chassis are the most inclined to fall off P4 track, you'd be well advised to at least consider trying a simple 0-6-0 compensation scheme where one axle stays rigid that is going to look something like this.

Having the jig simplifies fitting horn blocks. I would recommend the Highlevel horn blocks as the simplest to get to grips with. Folding them up is simplicity itself, click through the instruction here to see.

All you then need to do is

1. drill the chassis sides for the pivot been, half way between the compensated axles and a millimetre or two above the top of the axle holes (you can work it out exactly from the dimension of the wire/tube you use going to use for the beam - nothing less than 1mm), or guess and adjust the ride hight by bending the compensation beam)

2. remove the horn block cut-outs around the axle you need to compensate, these are usually marked these days but if not it a 6mm wide 7mm high chunk centred on the axle. In either case accuracy isn't critical. Make up your horn blocks, then solder them into the inside of each chassis side using the jig to ensure they are the right distance apart. All you need to do is ensure they go in with the chassis side level in the jig, and that each one is visibly vertical.

After that build the chassis as the instructions, remembering to fit the compensation beam as you go along.

Once you've done a couple you'll start to wonder what the fuss was all about and move on to doing the job properly with CSB's etc (but then I would say that wouldn't I)

Will

[Andy W]

Building a rigid chassis where all the wheels sit evenly on a sheet of glass (the usual way of checking) is far from easy. John Redrup, when he worked at Puffers, pointed this out to me when I showed him a wonky 0-4-0T I was trying to build many, many years ago.

To do so on a prototype with added axles/ponies etc gets progressively more so.

However, if you compensate/csb, or whatever, the wheels find the track themselves. I'm not saying you don't have to take care to get all the components level and square, but in many ways a flexible chassis is easier.

[Terry Bendall]

do P4 locos always have to have suspension?

Depends on the loco. Generally converted R-T-R models of diesel and electic prototypes don't as Dave (Tor Gifford) has said. We have two Bachmann 08s that run very well on indifferent track with no springing or compensation. There is however some movement on the centre axle which helps. There is however a valid argument that the sprung diesel bogies that have been developed make the running more realistic.

As othere have said, there are many examples of sucessful conversions of steam outline R-T-R models that work perfectly well without springing of compensation but an etched chassis kit, or a scratch built one will almost always need something.

Terry Bendall

[adigill]

Thankyou for all your reply's. It look's like some sort of compensation is the way forward. I think that I'm abit impatient and keen to get something running as I now have a number of wagons and coach'es ready to go.

[HowardGWR]

Is there any experience out there with the AG P4 conversion packs for steam RTR? I am hoping that the experience is positive, because it will be the only way i am ever going to get a P4 steam loco working that that does not bind. Having read Chris Pendlenton's experiences in MRJ 200, it put me off for life.

[David Thorpe]

I converted a Hornby Black 5 using the Gibson set. Apart from that, everything was original Hornby except for crankpins on the front and rear drivers - I used the original Hornby ones on the centre set. Oh, and some washers to space the front and rear wheels out from the chassis. The result is a very sweet running loco.

DT

[jasp]

Terry B wrote:
"As othere have said, there are many examples of sucessful conversions of steam outline R-T-R models that work perfectly well without springing of compensation but an etched chassis kit, or a scratch built one will almost always need something."

While not entirely disagreeing with this staement, is it not a bit strange that a locomotive, built to wide tolerances (ie ready to run) will function without compensation whereas something more precision will require compensation, CSBs etc?
Could there be a message here?

Jim P

[Tim V]

Yes and no.

A RTR loco will run on P4 track, but it won't run as well as a loco built with whatever breed of compensation/springing you favour. And don't forget the point I made earlier, that the compensation is not just about road holding, but also about electric pick up. Also the new chassis would have a better motor, better geared for the job in mind.

Of course for those going down the route of on board batteries.....

[HowardGWR]

Tim, forgetting road holding and possible wobbles over switches and crossings, are you saying that converted RTR engines will also refuse to start or jigger along like my efforts? Have you evidence for that? I really think this is the crux for me. As long as the thing goes - every time - as a certain R G Williams rightly demanded at Pendon, and doesn't jib at low speed, I'll be happy.

I have yet to hear from anyone who did not get a satisfactory result (except Chris P to whom I referred) - I'm not talking bogie diesels and electrics (but would be talking 08s of course).

By the way thanks for prompt replies.

[John Donnelly]

but would be talking 08s of course).

I run a Hornby 08 with a straight wheel swap with no compensation or springing and it runs without stalling (although I did add additional pickups as the Hornby ones aren't great) or falling off on the curves and turnouts...

John

[Terry Bendall]

I run a Hornby 08 with a straight wheel swap with no compensation or springing and it runs without stalling

And we have two Bachmann 08s also with extra pick ups which run just as well.

Terry Bendall

[Tim V]

What I said was that if you would be satisfied with running not markedly better than RTR, then you can just re-wheel as others (and myself) have done.

If you want the bees knees of running, you have to expect to put more effort in. And that is looking at running in the round, so smooth starts and stops, smooth road holding, reliable pick up.

The 08 is not a good example to pick on as a RTR sample, as I believe the motor is very well geared down, so you are some of the way there already.

[Terry Bendall]

What I said was that if you would be satisfied with running not markedly better than RTR, then you can just re-wheel as others (and myself) have done. If you want the bees knees of running, you have to expect to put more effort in.

I am sure that Tim is right on this. I have not converted any RTR steam outline models so no experience of that. The diesels that I have converted appear to run very well - at least to my satisfaction, but not having tried springing on diesels or seen such beasts working I have no comparison to make. The locos used on Ravenscroft Sidings and Elcot Road run well at slow speeds and move smoothly which is sufficient for us. A sprung loco maay well work better and we would be happy to try one out at some stage when we are at a show.

Terry Bendall

[Philip Hall]

Howard,

I think it should be remembered that Chris P approached the job in his usual precise manner, for as he wrote many years ago, he 'only knows one kind of OK running' and he has his own well engineered ways of getting very impressive results. He had, it seems to me, a very unusual Hornby chassis, where the coupling rods did not match the chassis holes. I say unusual because I must have converted thirty or more Hornby engines (although only about six or seven prototypes) to either P4 or EM, and they have all run impeccably. Some of the M7s have even been used as guinea pigs to sort the bugs out of an extensive EM layout.

I have had slightly less success with Bachmann (again, only about six or seven prototypes) simply because, as has been documented on here in the past, I have found that in many cases the coupling rods do not match the chassis slots. Correction of that is not difficult and is somewhere on the forum so I won't repeat it. Unfortunately I only have limited Internet access at the moment so can't look it up.

In many of these cases I have used Alan Gibson wheelsets and all has been well. I always check that the wheels are concentric, which they usually are, and basic checks that the crankpins are at right angles to the wheel centres are worth doing. I think that now Hornby have gone down the road of slots in the chassis rather than bearings, I shall start to check the first few as with Bachmann, but that may not be necessary.

If you doubt your abilities in all this, then I would recommend the Ultrascale drop in conversion packs, which are very accurate and give a pretty well guaranteed result. Yes, they are more expensive than Alan Gibson's, but so much of the difficult stuff, like quartering and swapping the gears, is done for you.

Finally, Tim is quite right, if you seek the very finest quality of running, then a new chassis is the only way to go. But these RTR chassis are now very good indeed, and a great way to get started. I have many kits to build, but there is no way I would ever build a T9 or a M7 - the ones I have run beautifully and pull well. I also recently saw a Bachmann C class on a P4 layout and the slow running was impeccable. And I like to think I'm quite fussy.

Philip

[HowardGWR]

Philip, this is what I needed to read, as I am well aware that you have this huge experience in this type of conversion. Thanks to Terry's evidence, but it is the coupling rod equipped engines I am interested in and thanks to Tim also. As my own underframe construction efforts until now have been inadequate (one small reluctance to move or slight hiccup in the dead slow running is failure in my eyes), I will try a conversion pack, perhaps a 57xx to start with. In my professional life I always reckoned that one gets what one pays for, or somewhat less, so Philip's remarks are noted.

If mods could help me find the article on the forum to which Philip refers I would be grateful; perhaps it had an unusual title? A search with "P4 conversion" brought up loads of posts (which I shall set about reading, you gather I have a lot on which to catch up) but not the one to which Philip specifically refers. It is that subject of possible correction of minor errors, referred to by C Pendleton, that frightens me to death, as my previous attempts at correcting my own 'binds' ended in 'failure', sometimes disaster (wheels coming loose through too much fiddling being a prize example).

[Horsetan]

Is there any experience out there with the AG P4 conversion packs for steam RTR? I am hoping that the experience is positive, because it will be the only way i am ever going to get a P4 steam loco working that that does not bind.

Technically speaking, an 08 with its outside cranks will fulfil similar criteria to a steam 0-6-0. I used the AGW conversion pack for the 08, no trouble at all, and the result actually runs alright.

I still don't like the Hornby motor, or the worm gears, but that's just me.

Having read Chris Pendlenton's experiences in MRJ 200, it put me off for life.

Chris Pendlenton tends to take things much much further than most other people. If it wasn't for him, you'd never realise there was a flaw.....