Sickly Bachmann K3

[micklner]

Can anyone assist with the following problems , Bachmann want £20 plus parts just to look at it. I will either fix it or get another from Ebay as it would be cheaper than returning it to them.!!.

 

This is what I sent to them

 

 

I have a LNER version of the Bachmann K3. I have a problem with the valve gear on the offside of the loco. The radius rod instead of being fixed is sliding backwards and forwards as the motion turns. I have looked at both sides and nothing appears to be missing/broken. The nearside is also loose but for whatever reason does not slide backwards/forwards when the motion turns. The loco has only had light use, and otherwise runs very well.

 

 

I use code 75 track and have contining problems with the K3 tender derailing , also the same on a J39 I have. This is mainly when running in reverse through medium size points .I have checked back/back measurements and cleaned the wheels without no change of either tender behaviour. Both tenders have wheels with quite deep flanges, any suggestions as to what they can be replaced with ? , Gibson/ Markits ?

 

 

Mick

[davidw]

Back to backs?

[StaffsOatcake]

add some weight inside the tender plasticine works a treat

[micklner]

Thanks I will add some weight to the tenders.

 

Anyone any ideas re the Valve Gear please ??

[Guest Max Stafford]

If the radius rods are flopping rather than turning on the crankpin as they should, it's possible that the cranks are incorrectly seated. Try undoing the fixing nuts and re-seating, one at a time, the cranks. The little end should line up with the centre of the axle.

 

Dave.

[micklner]

If the radius rods are flopping rather than turning on the crankpin as they should, it's possible that the cranks are incorrectly seated. Try undoing the fixing nuts and re-seating, one at a time, the cranks. The little end should line up with the centre of the axle.

 

Dave.

 

I dont think we are talking about the same part of the valve gear?

 

http://en.wikipedia....erts_valve_gear

 

The part I am talking about on the diagram is shown as the radius rod (8) it is sliding to the left and right when the wheels turn. On the left behind the expansion link(7) , to the right the rod and the the valve stem (13) is also moving in and out of the cylinder.

I havent so far removed the chassis from the body I am wondering if there should be something locating the combination lever (12) or holding the valve stem (13) where it enters the cylinder area ? There is nothing stopping the lifting link (4) if its even there ? from moving therfore the radius rod is loose !!

 

Having now looked at the link myself it shows the radius rod moving backwrads and forwards . I have never seen this on any model they are always fixed retail and kits I have made . Perhaps I should give up at this point ??and ignore it and be impressed with the detail !! It would appear Bachmann service dept dont know either

 

cheers

 

Mick

[gordon s]

I dont think we are talking about the same part of the valve gear?

 

http://en.wikipedia....erts_valve_gear

 

The part I am talking about on the diagram is shown as the radius rod (8) it is sliding to the left and right when the wheels turn. On the left behind the expansion link(7) , to the right the rod and the the valve stem (13) is also moving in and out of the cylinder.

I havent so far removed the chassis from the body I am wondering if there should be something locating the combination lever (12) or holding the valve stem (13) where it enters the cylinder area ? There is nothing stopping the lifting link (4) if its even there ? from moving therfore the radius rod is loose !!

 

Having now looked at the link myself it shows the radius rod moving backwrads and forwards . I have never seen this on any model they are always fixed retail and kits I have made . Perhaps I should give up at this point ??and ignore it and be impressed withe detail !!

 

cheers

 

Mick

 

 

OK. Two things worth checking Mick. I'm assuming it's the same/similar to the Ivatt valve gear.

 

1. Check the pivot hasn't come out of the holes.

 

2. Check this link is seated properly. There are a couple of pips that prevent it moving upwards.

 

[Guest Max Stafford]

Thanks Gordon, I'm away to read 'Steam Locomotive Anatomy 101' again...

 

Dave.

[micklner]

Thanks for all the replies

[34theletterbetweenB&D]

The radius rod should be anchored at the rear end by a small pin on the inside of the weighshaft (aka reversing rod) lever representation. Possibly the pin is simply disengaged, the weightshaft lever is a fairly bendy piece of plastic; I have had to alter the weighshaft lever position on a couple of mine so that this pin restrains the rod. Without this restraint, the radius rod pretty much moves back and forth with the crosshead, which isn't right at all.

 

The one time I had trouble with a K3 tender not staying on the rails in reverse it was the loco to tender coupling bar slightly mispositioned so that some weight from the loco was resting on the tender and tending to lift the rear tender wheels. On the J39, the derailing tender problem is simply solved by removing the loco body securing screw from beneath the cab (it isn't required, the body is a tight fit on the chassis). This screw head will catch the top of the tender coupling pin unless the track is perfectly smooth: this tends to both lift the rear of the tender, and prevent it swinging relative to the loco to take a curve, and can derail the tender with the loco going forward.

[micklner]

Hi

The pin is there on both sides however the rod slides back on both sides at least a further 3 or 4mm before it reaches a full stop against the bracket moulding. All the pin does is locate itself in the slot in the rod and therfore prevents any vertical movement .

Should it be glued to the rod or is that normal design for a K3 please? I only have the one K3 so have nothing to compare it with.

 

thanks Mick

[gordon s]

OK Mick, lets go back to square one. Managed to find my K3 and here's the valve gear. Which side is the problem? The left or right looking forwards from the cab?

 

[micklner]

As mentioned earlier both sides are "loose" the nearside as per the picture has no more than 1mm of movement when running and can only be seen at very low speed. The offside has the main movement problem much more exagerated movement at all speeds

 

cheers

 

Mick

[Theakerr]

I have my K3 in front of me. As I see it Bachmann have essentially done what Hornby did years ago. The radius rod is supposed to move so that it in turn generates movement in the valve stem. Unfortunately the pivot for the combination lever is not "hidden by the valve stem guide as it should be, so the movement, which is generated by the union link and combination lever, is exagerated. I believe this is as designed although it sounds as though it may be extreme on your model. Wonder if the pin that holds the radius rod behind the expansion link is broken or if the the radius rod has become detached.

[micklner]

I have my K3 in front of me. As I see it Bachmann have essentially done what Hornby did years ago. The radius rod is supposed to move so that it in turn generates movement in the valve stem. Unfortunately the pivot for the combination lever is not "hidden by the valve stem guide as it should be, so the movement, which is generated by the union link and combination lever, is exagerated. I believe this is as designed although it sounds as though it may be extreme on your model. Wonder if the pin that holds the radius rod behind the expansion link is broken or if the the radius rod has become detached.

 

Pin is in place as far as I can tell and the rod is in situ

[gordon s]

Not sure if this will help or not. Set up my K3 on a rolling road so at least we can see the movement of the various parts. If all else fails Mick, new valve gear is available from Bachmann and will cost around £6.

 

[Guest TomTank]

Hi Mick

 

I no exactly the problem you have, as one of my K3s (BR late crest) does exactly the same think, sort of sliding towards the pistons and back,

I had sort of ignored it thinking that it was just how Bachmann had designed them, but after seeing Gordon S's footage, I see thats no the case.

 

I'm going to test my other two K3s (LNER and BR Early Crest) and see what they do.

 

I'm guessing as someone else has said, there could be a pin missing.

 

Tom

[coachmann]

On the Bachmann K3, the pistol rod is drawn back and forth by the combination lever seeing as it is pivotted above another pin. The back end of the radius rod is slotted to pass through the central pin of the expansion link. In effect the valvegear is in nuitral.

 

The only exaggeration of movement on such motion could be caused to the return crank rod if the return crank was moved to the rear or forward of the driving wheel centre, but it would not be transmitted to the radius rod on Bachmann valvegear.

[micklner]

I have taken the offside gear off at which point the rivet at the bottom of the expansion link fell out. Nothing obviously wrong. I bent the lifting arm bracket which has the pin thereon in as far as I could persuade it. Reassembled and it is all back to normal as per the nearside of the loco.

I have no idea what the problem is or was ?? but its cured itself at the moment so I will leave it well alone!!

Out of interest and for future information , how do you get the body off ? I removed the screws front and rear of the chassis , the tender bracket refused to come out and I didnt want to force it.

 

 

many many thanks for all the replies

 

Mick

[Theakerr]

The video is most interesting. On mine the valve stem moves. In the video it does not. The conclusion I draw is that the valve stem is not supposed to move and the fact that it is (and it is different on each side) is the problem. Mine does run OK but over the next while will take it apart. I suspect a bit of Super Glue will deal with it sould I feel it is necessary.

[34theletterbetweenB&D]

... Out of interest and for future information , how do you get the body off ? I removed the screws front and rear of the chassis , the tender bracket refused to come out and I didnt want to force it.

The loco to tender drawbar has to come out for the body to part from the chassis. Once the screws are removed, lever it up and down, until the body and chassis begin to part at the rear, then withdraw the drawbar. The chassis should then drop down vertically out of the body, but it is always tight the first time. If it doesn't want to shift, try getting a lever between the chassis block and the body at the front above the pony truck, to help get things moving. On two of my examples the adhesive securing the footplate stays to the chassis block was still presumably tacky when the loco was assembled as there was some adhesive action between the body and the chassis which are very close fitting; a little more brute force was necessary.

[GER]

The radius rod should be anchored at the rear end by a small pin on the inside of the weighshaft (aka reversing rod) lever representation. Possibly the pin is simply disengaged, the weightshaft lever is a fairly bendy piece of plastic; I have had to alter the weighshaft lever position on a couple of mine so that this pin restrains the rod. Without this restraint, the radius rod pretty much moves back and forth with the crosshead, which isn't right at all.

 

The one time I had trouble with a K3 tender not staying on the rails in reverse it was the loco to tender coupling bar slightly mispositioned so that some weight from the loco was resting on the tender and tending to lift the rear tender wheels. On the J39, the derailing tender problem is simply solved by removing the loco body securing screw from beneath the cab (it isn't required, the body is a tight fit on the chassis). This screw head will catch the top of the tender coupling pin unless the track is perfectly smooth: this tends to both lift the rear of the tender, and prevent it swinging relative to the loco to take a curve, and can derail the tender with the loco going forward.

    Whilst late in the day on the topic of the J39 I have solved the derailing tender problem by simply moulding a small amount of Blu-tack on the top of the tender coupling pin. Then when coupled ensuring the loco wheels and tender wheels are all sitting on the rails prior to movement of the loco in either direction.  At normal operational speed all is well.