U Class Valvegear/motion assembly

[WKDOR]

My ancient Zillertalbahn 2071D has had quite a lot of disassembly.

Every time I come to put it back together I struggle with the pivots/pistons/slidebar sub-assembly.

Following John Lythgoe I hope I've got the quartering right and the LGB left-hand rule:

"left crank at 12 o'clock, the right is at 9 o'clock"

But what about the rest?

LH at 12:00

RH at 09:00

Will this work?

Mike

 

[WKDOR]

And if not, can you please doodle on my pix where it should all be.

Many Thanks in advance

Mike

 

[Neil Robinson]

As far as I can see all is correct.

 

[Tony]

What is the problem when you try and run it does it appear to bind after half a turn ish ?

Tony

 

[WKDOR]

Thanks Neil, that's very reassuring.

Tony, in the past it has binded/bound and lurched/lolloped a bit.

I don't know whether its doing that now because its been in pieces for a battery/sound conversion and will take me a day or two to get it back together. Then I'll let you know.

Mike

 

[Tony]

There is a very strong danger that im going to confuse myself here let alone you but

The axle that has the drive spocket will move the conrods on both sides the move the other axles

It will push the wheels on one side and at the same time Pull the wheels on the other side

Bear with me

There is always some play in both ends of the conrod where it connects to the other two wheels

Even though it may look like you have the wheels alligned (all at 12 oclock)

if you have one of the non drive wheels one spline out

(im getting lost)

When the wheels turn and the conrod goes from push to pull (bugger)

Ok drop the motor so the wheels can turn freely remove one side (wheels) and make sure the fitted wheels all start to move at the same time
Now refit the motor so wheels cant turn
then refit other wheels making sure they all are Strained against each other in the same direcrtion

Believe me i know how to do it i just cant explain it in words
i will try and draw a diagram
sorry if ive made things worse
Tony

 

[Tony]

"

i know its over the top but the wheel with the red cross could be 1 or even 2 splines out on the axle and it would still look correct so in other words make sure when you turn one wheel that the other two move at exactly the same time

Hope it helps Tony

 

[Tony]

Ok just layed in bath working it out

the bottom diagram will work while say the center axle is pushing the other two but when it gets to the bottom and starts pulling the other two there is no room for the out of line wheel to accomadate the conrod so it will bind as it is held fast and being driven by the other side wheel
Yes thats it
Your still none the wiser are you
Tony

 

[WKDOR]

Well I'm very grateful Tony and I am trying.

Got as far as taking wheels off on one side and am beginning to see what you're saying - I think.

Will have a longer try in daylight.

Many Thanks again.

Mike

 

[Bredebahn]

Something doesn't look quite right with the droplink somehow - might be me. Got to pop out to the dentist now but I'll dig out some old pictures of when I rebuilt the gear on my U class some while ago and I'll post these up for comparison.

 

[Neil Robinson]

If ever I have doubt on the quartering of the wheels/mesh of the motor gears I use the following method to check by eye.
As previously mentioned, there is plenty of play designed into the LGB mechanism so there is no need for absolute precision.
With the motor in place hold one of the end axles, in the illustration it's the right hand one, rigid with the balance weight vertical and rotate the other end axle in both directions as far as the gear backlash and motor endfloat will allow. It should move by approximately the same angle from the vertical in both directions, I hope the diagram makes this clear. To make doubly sure I then hold the left hand axle rigid and repeat the test. If I think adjustment is needed I move one driven gear by one tooth relative to the motor worm and repeat the test.

Once I'm happy I then check the other side of the loco. If one side is fine, but the other is out it is most likely that one wheel will need to be removed from and replaced on its axle in a slightly different position. On an electrically powered model the relationship between the quartering on one side relative to the other makes no difference to smooth running, but it may look unprototypical if set badly. It's unlikely to be noticed though as it's not easy to see both sides of the loco at the same time.

 

[Spule 4]

Your quartering and cranks are fine, any binds I have had with LGB have been a gear bind, follow Niel's comment about gears. On the U the two outer axels are driven, the center is along for the ride.

 

[Bredebahn]

I think my U Class looks different as it's a later model with plastic valvegear. The only LGB loco that I've had that gave trouble and kept shedding the gear - normally breaking bits in the process. Now that spares are tricky to get hold of this loco will only run very carefully (although since the rebuild there have been no further problems, the thickness of the plastic gives me cause for concern in places).

This picture was taken with the new gear fitted and just the one screw to be inserted to hold it all together. I have a series showing the complete removal of gear and cylinders, and refitting with new if anyone needs it.

 

[WKDOR]

Well Thank You Everybody.

I gleaned all the best bits and followed the collective wisdom!

Reassembly went much more smoothly and running on blocks looks better too. Can't track test yet, but any further devlopments and I'll be back.

Many, many thanks again

Mike