Wheel quartering issue

[hayfield]

Some time ago I bought a built High Lever 57xx chassis in P4 gauge, its been very well built and painted, but was missing its coupling rods and brake gear. I had a set of Gibson Coupling rods and Chris at High Level supplied me with some brake gear. I realise there may be a few issues as the chassis has been built to fit a different set of coupling rods

 

Yesterday I had time and the inclination to build and fit the rods, I always seem to have issues with quartering wheels that is why I have in the past steered away from Gibson wheels, but feel now is the time to learn how to fit and adjust them properly. The chassis is sprung (CSB I think), the drivers with the gear on does allow a bit of quartering adjustment. I can get the driven and centre wheels to work smoothly, and when I couple the 2 non driven pairs of wheels they also run freely, but when all 3 pairs of axles are fitted there is a slight snatching. I guess I can open up the holes a bit more and at worst all I have done is ruin a set of rods, but any thoughts or tips on how I can proceed please

 

Thanks

[Ruston]

Have you used a GW wheel press to put the wheels on? If you have then the quartering is taken care of when you put the wheels on. If not then I recommend getting one and refitting the wheels with it. It's definitely worth buying if you're intending to use Gibson wheels in the future.

[Michael Edge]

Have you checked that the rods match the frames? I use a Poppy jig to check this but a set of axles with the ends turned down to crankpin size will do the job. In the absence of either place one rod on one side and run all the wheels round together with your hand, this will detect any tight spots. Repeat for the other side before making any adjustments to the quartering.

[John Tomlinson]

If it isn't teaching you to suck eggs, have you tried looking through the spokes to see if the wheels on each axle are in the same place relative to the other wheel on the axle?

 

John.

[hayfield]

I have one of these presses, but as I said I bought the chassis ready made, the wheels were pre-quartered, the set with the gear on can be adjusted, but the other to are locked solid. Also they are Gibson rods in a High Level chassis and I expect the chassis has been built to match the High Level coupling rods

 

I have eased out the holes in the coupling rods a tad and the loco runs better, very slow speed is the issue where there is snatching in two places (12 and 3 o'clock) 

[hayfield]

2 minutes ago, Michael Edge said:

Have you checked that the rods match the frames? I use a Poppy jig to check this but a set of axles with the ends turned down to crankpin size will do the job. In the absence of either place one rod on one side and run all the wheels round together with your hand, this will detect any tight spots. Repeat for the other side before making any adjustments to the quartering.

 

Michael

 

Thank you for the suggestion, as it happens I have a Hobby Holidays jig I can use. But the wheels are already fitted (P4 Gibsons) and I am loather to remove them

 

Will give your suggestion of 1 rod at a time, but with only 2 pairs of axles fitted at a time both pairs run fine

[hayfield]

5 minutes ago, John Tomlinson said:

If it isn't teaching you to suck eggs, have you tried looking through the spokes to see if the wheels on each axle are in the same place relative to the other wheel on the axle?

 

John.

 

John

 

Thanks, I have been comparing the straightness of the coupling rods, Never before understood the method at looking through the chassis for alignment before, thanks for the tip

[Izzy]

Are these Gibson rods in two parts that overlap on the centre crankpin? I am assuming from what you have posted that the drive is from the outer axle of a 6-coupled loco? The issue tends to suggest to me that the rod centre measurements might be altering during rotation, (always assuming they actually match the wheelbase - take nothing for granted).

 

It’s a problem I have often encountered with split rods. When the drive is to the middle axle any slop between the two rod halves tends to be cancelled out, but with an outer axle gets compounded. My solutions are either to solder the rods up solid or pin them together as per the real things, either case meaning the rod centre measurements stay constant. This problem often afflicts recent RTR where jointed rods are sloppily assembled needing similar remedies to get decent running. So long as there is a modicum of play of the rods on the crankpins it works quite okay with ‘flexible’ chassis whatever means are used, sprung/compensated etc.

 

With regard to quartering using sighting through the spokes, they don’t need to be set at ‘exactly’ 90 degrees. Aligning the spokes is easier to see/do and if the subsequent quartering is somewhere between say 88 - 92 degrees it’s quite good enough to ensure decent running, as long as all wheel sets are the same of course!

 

Izzy

[30368]

Some good advice offered, I use the Poppy Jig too it works well. Can I ask if anyone knows where I can purchase the GW wheels press?

 

Kind regards,

 

Richard B

[30368]

Agree Izzy, generally best to solder split rods together and do this on a Poppy Jig or similar as below, sorry not a great picture!

 

 

Kind regards,

 

Richard B

[Brassey]

Can't use solid soldered rods in a P4 CSB chassis as that will counter the desired compensation/springing.  Gently opening the holes with a tapered broach is probably the best solution here short of rebuilding the whole chassis

 

PS: you should be able to get a GW wheel press at Scaleforum at the end of this month otherwise check out the ads in MRJ for mail order

 

edit for PS

Edited September 7, 2019 by Brassey

[Michael Edge]

18 hours ago, Izzy said:

Are these Gibson rods in two parts that overlap on the centre crankpin? I am assuming from what you have posted that the drive is from the outer axle of a 6-coupled loco? The issue tends to suggest to me that the rod centre measurements might be altering during rotation, (always assuming they actually match the wheelbase - take nothing for granted).

 

It’s a problem I have often encountered with split rods. When the drive is to the middle axle any slop between the two rod halves tends to be cancelled out, but with an outer axle gets compounded. My solutions are either to solder the rods up solid or pin them together as per the real things, either case meaning the rod centre measurements stay constant. This problem often afflicts recent RTR where jointed rods are sloppily assembled needing similar remedies to get decent running. So long as there is a modicum of play of the rods on the crankpins it works quite okay with ‘flexible’ chassis whatever means are used, sprung/compensated etc.

 

With regard to quartering using sighting through the spokes, they don’t need to be set at ‘exactly’ 90 degrees. Aligning the spokes is easier to see/do and if the subsequent quartering is somewhere between say 88 - 92 degrees it’s quite good enough to ensure decent running, as long as all wheel sets are the same of course!

 

Izzy

Overlapping rods on crankpins is perfectly acceptable practice, it was used on many full size locos - notably LNW 0-8-0s and some Hunslet diesels.

[John_Hughes]

17 minutes ago, Michael Edge said:

Overlapping rods on crankpins is perfectly acceptable practice, it was used on many full size locos - notably LNW 0-8-0s and some Hunslet diesels.

 

Agreed - but the tolerances on the prototype are probably quite a bit tighter than the inevitably sloppy fit of model coupling rods, where we have such factors as not-quite-identical crankpins, slight wheel wobble and so on to deal with. I suspect it's no accident that so many RTR 0-6-0 locos have the motor driving the centre axle.

 

Actually I'd guess that even on a CSB chassis, solid rods won't actually impede the springing too much. After all, we're only talking of fractions of a mm displacement, surely?

[Izzy]

I've been playing around with sprung/compensated loco chassis in various scales, but mainly P4, for around 40 years, and during that time have found that, under certain circumstances, whether they work in full size practice or not, some aspects sadly just don't with models. Or lets say not to the running standards I am happy to accept. This is particularly the case with locos where the driven (model) axles are not the same as on the prototype, and as has been said tolerances also come into play. I have used rods pivoted around the centre crankpins as a lap joint - mainly Gibson's ( I designed the 'universal' ones), pinned correctly, and solid. This is with many different design of chassis axle movement.  My view now is that solid rods with a modicum of play on the crankpin to allow some axle movement are the simplest/easiest option. The idea that locos need to be able to climb over sleepers, as used to be promoted as what is needed, is a bit wide of the mark, 0.5mm is more than enough. 

 

This is the last P4 build with solid rods. Done a year or two ago, I'm mostly 2mm now.

 

it looks (is) fairly crude, an old Whitbourne models chassis I had lying around and thought I'd make up for something different.

 

Sorry to Hayfield for invading his thread.

 

Izzy

 

 

 

[Michael Edge]

On 07/09/2019 at 08:51, John_Hughes said:

 

Agreed - but the tolerances on the prototype are probably quite a bit tighter than the inevitably sloppy fit of model coupling rods, where we have such factors as not-quite-identical crankpins, slight wheel wobble and so on to deal with. I suspect it's no accident that so many RTR 0-6-0 locos have the motor driving the centre axle.

 

Actually I'd guess that even on a CSB chassis, solid rods won't actually impede the springing too much. After all, we're only talking of fractions of a mm displacement, surely?

If it works full size it will work in a model - I couldn't count the number of people who have told me that you have to drive the middle axle and of course it's impossible to drive from a jackshaft. The main difference with full size is that the forces involved are much greater, run down locos could have very sloppy coupling rods.

[John_Hughes]

14 hours ago, Michael Edge said:

If it works full size it will work in a model - I couldn't count the number of people who have told me that you have to drive the middle axle and of course it's impossible to drive from a jackshaft. The main difference with full size is that the forces involved are much greater, run down locos could have very sloppy coupling rods.

 

Yes, of course; if it works full-size it will indeed work on the model - except that you can't scale down either tolerances or physics, and our usual model tolerances, using commercial products, are way, way over scale.

 

Sid Stubbs of blessed memory could do it, and many others have done it as well, so it's not impossible, and I never said it  was; but in my bodging experience, it can be tricky, and I like to keep things easy because I get more done that way.

[5050]

All my 0-6-0 P4 locos are compensated, driven on an end axle and have rods pivoting on the centre crank pin.  They all seem to run OK.  I use Gibson wheels with their crank pins and fit them using a GW wheelpress and use Perseverance 'jig axles' when fitting the hornblocks etc.  I make sure the crank pin holes in the rods are 1.5mm to fit the jig axles closely and then open up to 1.6mm for the first run test.  If necessary I will then ream out very lightly as required to achieve good smooth running.

[hayfield]

Thanks everyone for your replies and suggestions, sorry for the delay in responding but a holiday in Italy got in the way

 

It may be the main issue is that I bought the kit built but missing items, its a High Level kit and I am using Perseverance coupling rods. I have used broaches to open out the holes trying to get smooth running, as it happens they are Gibson crankpins and the rods will need opening further to accept the bushes. Another thought is that I may have soldered then together slightly out of register ? Don't think so as I was careful.

 

I will have another go at opening then a bit further (at worst all I have lost is a pair of coupling rods, any thoughts on how to decide which set of wheel set holes to open out first please

[DCB]

My usual conspiracy theory is the kit was sold minus rods because the previous owner had the same issue.  For a sweet running chassis I believe the chassis should be assembled using the  coupling rods to act as a template.   It sounds like the rod centres and axle centres don't match, opening up the crankpin holes in the rods may prove to be a short term fix but its a bodge.

My approach would be fit the rods and run the chassis in. If it doesn't have a motor or body stick a bit of lead on it to compensate for the missing weight and tow it around the layout while you have your "Tea" changing direction before you start your pudding. That may be all it needs. If that don't work you could always stick it back on eBay.    I had similar trouble with a Dean Goods, it snapped a side rod and I spent ages trying to fix it. Eventually I took the wheels and motor off and stamped on it so I wouldn't waste any more time on it.  (Then I straightened the frames and sold them on eBay)

[hayfield]

I have opened the rods out slightly and the loco is now running better, now I need to fit the Gibson bushes and crankpin nuts