Quartering loco wheels

[Tony MartyrParticipant @tonymartyr14488]

I am building a 3 1/2″ 2-6-2 William and have (obviously) made a minor error in quartering one of the wheel sets in spite of making a jig and taking as much care as I could.

The whole system rotates OK by hand but with a jerk at full stroke at either side.

Too much clearance in the bosses will cause the whole system to do very strange things!

If I ever build another engine it will have only 4 coupled wheels!

Do others have these problem?

Tony

[Tony MartyrParticipant @tonymartyr14488]

[WearyParticipant @weary]

Yes! 

If a balls-up is possible, and even on occassion when it is seemingly impossible I still manage cock things up.  Hopefully you can get the faulty wheel-set apart with minimal damage and re-set it, maybe using glue to allow a bit of faffing to get it absolutely exact.

Oh, by the way, even with four-coupled wheels the quartering can be out (how do I know this?), maybe best stick to ‘singles’?

[Tony MartyrParticipant @tonymartyr14488]

Perhaps the situation is not so grim as first appeared.

Removal of all cylinder gear has allowed me to run the chassis with all wheels coupled and, although not perfect, the wheels don’t jam when the chassis is pushed over a plastic tiled floor.

So perhaps I have a contact somewhere on the rest of the running gear – I will have to build it back section by section

My problem is that I have no idea how free a engine such as mine should turn by hand. (The pistons and stuffing boxes are not too tight) Nor do I know if the effort to turn the wheels by hand is constant – ?

[WearyParticipant @weary]

Certainly doesn’t sound like a quartering problem as your chassis seems nice and free-running.  

Fortunately it is often the way with model engineering that further consideration of a perceived problem shows that it is not as disasterous as first thought.

By your step-by step approach you should be able to isolate the point of resistance.

In my limited experience a firm grip is needed to turn a new engine over until it is run in on air.

It sounds as if you have the problem under control – (do you have clearance between the cylinder ends and pistons at full stroke?).

(It seems that only you and I have issues of this type!)

 

[Tony MartyrParticipant @tonymartyr14488]

As an apprenticeship served (when this meant 5 years of practice in every trade) mechanical engineer who has worked with ic engines all my life I find the most difficult part of building my first (probably last) locomotive is that I have little advance idea of which are critical and non-critical dimensions. I was advised by an expert not to be too ‘tool-roomish’ about the work but it is interesting to me that none of the critical items in the valve gear have any means of adjustment – you just have to get it right!

Anyway I have solved my problem which was very embarrassingly what Weary suggested – one of the pistons was bottoming because I had not adjusted the piston rod into the cross-head correctly.

“Mistakes are rungs on the ladder leading to ???” 

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