Scalefour Forum

Hi all

I've decided after years of modelling in em & 0 gauge it's time to push to boundary a bit & step up to P4. I've tried it once before but I wasnt skilled enough to model at such a high level.

I've now built many locos albeit rigid & it's time to push myself. I will be keeping it small & modelling industrials which I feel is achievable in a small space.

I've 10 rt models hudson tippers to build & wondered what my best options was regarding compensation? I was thinking of elongating the holes & adding a knife edge above the axles to give it a small degree of movement.

Do I need to compensate a wagon with such a small wheelbase? Modelling in em is simple, it can be made rigid but I assumed p4 wagons need some form of compensation?

My eventual aim is to construct a small layout that features a working incline so the wagons will be shunted & be travelling up & down.

Lots of theory says "must have compensation / springing" . Numerous people show in practise its not necessary, and depends on wheelbase and track quality. Sprung stuff which is "done well" (right spring rates, right weight, consistent across lots of vehicles) can make things look better when running. But done less well, and the rigid is likely to be better !

If your proposed compensation can keep the axles parallel, and moving smoothly, it may be fine. But, if they can be built much easier with all four wheels flat on a sheet of glass, I'd expect them to work fine. I'd be inclined to build a few rigid ones, then get a loco and incline working so shunting a few is possible. Then worry about compensation/springing when you've seen how a few rigid ones ride.


- Nigel

As Nigel says, you most definitely do not have to spring or compensate rolling stock in P4. I choose to spring my wagons, because I prefer it that way, but it is definitely not essential.
The short wheelbase will be less than that of most bogies and they do not need to be be so treated either.
Building a few and trying it is a very sensible approach. A little weight in the wagon will help.

Andrew Ullyott wrote:As Nigel says, you most definitely do not have to spring or compensate rolling stock in P4. I choose to spring my wagons, because I prefer it that way, but it is definitely not essential.
The short wheelbase will be less than that of most bogies and they do not need to be be so treated either.
Building a few and trying it is a very sensible approach. A little weight in the wagon will help.

Hi Simon,

Welcome to dipping your toe in the world of P4. But please don't think of it as a step up, more just doing something different. Yes, some of the challenges won't be found in other scales/gauges, but neither will some of the pleasures. It's all a compromise, so I hope you enjoy it.

You've already had excellent advice from Nigel and Andrew. I just wanted to emphasise that bit above. If you aim to get as much weight as you can into these wagons, and make that weight consistent across them, then it will help a great deal.

It's usually talked about as 50g being a good target weight for a four-wheel wagon. That works well as a rule of thumb. However I'm confident that you'll struggle to get anywhere near that weight in these sort of wagons, so give it a go and see what you can do. There is very little black and white in this game, as I'm sure you know.

And do just ask on here. We don't bite (much)...

Cheers
Paul

Thanks for the advice gents,

I have always been of the assumption that everything in p4 must be compensated for the trackwork. I suppose if one or two detail it will be quite prototypical I suppose.

I've built a few beers tippers before for a friend & they were a lovely model to make.

I've a mercian models barclay diesel currently out on my bench as I am formulating a plan of attack for my first loco with hornblocks & a compensation beam.

I shall start a modelling workbench thread when I've got something going to share my work.

It's very easy to make stock that won't stay on your track so when you're starting why not go for something that is almost certain to work rather than pick a solution that should be alright if you can make very good track at your first attempt. Yes, you can clip new wheels into a Bachmann mineral wagon or coach and it will perform well but making something as flat and square isn't as easy as it sounds.

You've come from 0 gauge which I've always thought runs very roughly compared to the best that we're achieving in P4 so why not move on from your traditional thoughts on compensation and follow the trend into springing. There's no point in working to the tighter tolerances which P4 requires without aiming to get a better result than you were achieving in the more approximate scales.

DaveB

Hi Dave

I have thought about springing & I think I might have a go at some point. I've always stayed away from any hornblocks etc so this little barclay I feel I can achieve a running model with a compensation beam.
I would like to have a go at springing & I think at some point I'm going to have a go with a j94 chassis. I'm taking things slowly & doing what I feel I can achieve rather than going in at the deep end.
I will get there, I dont give up I just need to digest a bit more on the springing side of things before I'm confident enough to try it.

Simon Moore wrote:Do I need to compensate a wagon with such a small wheelbase? Modelling in em is simple, it can be made rigid but I assumed p4 wagons need some form of compensation?

Nope. Just build the chassis on a piece of glass. As it’s inside bearings it wouldn’t hurt to extend the slots downwards at one end but a bit to give a little flex.

Jim

I agree with those who advise to avoid 'compensation'.
In my experience, with relatively light weight 4 wheel wagons, rigid but square works as well as, if not better than, having one axle rocking especially if that axle is leading over small radius pointwork.
I would suggest trying one wagon with all the bearings opened out to a free sliding fit, say 2.1mm over a 2mm axle.

Ted.

I spring for 4 reasons:

1. Sprung vehicles look better in motion.
2. They're quieter (since that nice Mr Bradwell alerted me to the row made by unsprung vehicles I haven't been able to go back)
3. Job satisfaction.
4. It's P4 - it's meant to be done right.

I agree that sprung vehicles ride better, however have you been to a heritage railway where they have run a demonstration freight and listened to the noise?
The leaf springs on 1950's and earlier wagons are not soft and act more like a shock absorber, hence the noise on joints and crossings.

Gordon A

Got a Mercian Barclay on the bench? This MAY help you in a small way -

https://www.rmweb.co.uk/community/index ... l-shunter/

Regarding your initial enquiry, I would think, as others have stated, that a short wheelbase vehicle, built well, should work fine and will bump and jar just like the real thing did. Industrial tippers/hoppers didn't float. I run several RTR wagons with just the wheels changed. I reckon they run fine - but then, I'm a heretic....................

Enigma wrote:Got a Mercian Barclay on the bench? This MAY help you in a small way -

https://www.rmweb.co.uk/community/index ... l-shunter/

Regarding your initial enquiry, I would think, as others have stated, that a short wheelbase vehicle, built well, should work fine and will bump and jar just like the real thing did. Industrial tippers/hoppers didn't float. I run several RTR wagons with just the wheels changed. I reckon they run fine - but then, I'm a heretic....................

Enigma

This is brilliant!

I was thinking of driving off the leading axle with the rear 2 drivers compensated but wasnt sure how it would work.

I will be reading this with interest & taking notes for my build. May I ask which high level gearbox you used ?

Er, you can ask - but I probably won't remember! I'll have a look through my stack of 'used' instruction sheets, there may be a clue there. It's probably one of Chris's more recemt productions going by the grub screw gear fixing.

Glad to hear the thread may be of use to you.

EDIT - I think it is a Loadhauler Compact - gear ratio to choice

steamraiser wrote:The leaf springs on 1950's and earlier wagons are not soft and act more like a shock absorber, hence the noise on joints and crossings.

Gordon A

Sorry to be so picky, Gordon, but it is the springs that are the shock absorbers, and the friction between the leaves that do the damping. The rust between the leaves on old wagons increases the damping rate, consequently the noise. Blame the motor trade for calling the combined spring/damper units 'shocks'.

Respectfully,
Ted.