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Subject: K28 runs stiffly in reverse

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llynrice

1st Class Member
Cornwall, Vermont
Foreman

Foreman
Posts:167

05/07/2008 7:04 PM
I've run my new K28 enough now that I'm beginning to have a pretty clear idea of how it behaves. Running forward, it runs smoothly and pulls well. With one load of fuel, it will steam for an hour with two brief pauses to pump more water into the boiler. It does not run nearly so well in reverse. It hesitates with each wheel rotation as if it were binding. I see no evidence that there is any mechanical binding and sort of expect that there is some problem with the valve adjustment. Have any of you had problems such as this? Any thoughts about setting it up to improve running in reverse? Llyn

Llyn Rice Cornwall, Vermont *Vermont Scenic Railway*

Taperpin

Brakeman
Posts:45

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05/08/2008 2:08 AM
Lyn, its almost certainly the valve events..open the chest covers and watch while slowly rolling the loco forwards and then backwards.[keep going in one direction for 2 wheel revolutions to avoid backlash..watch the opening of each valve end/port..and note the position of the crank pins..you wont get it equal in both directions but try to get the opening moment even.in forand rev.watch out for the expansion link swing not being equal also you may have to very slightly adjust the return crank position. If you have to compromise , its best to favour Forward gear for obviuos reasons.

llynrice

1st Class Member
Cornwall, Vermont
Foreman

Foreman
Posts:167

05/12/2008 12:16 PM
What a difference! I started with your suggestions. Then I checked the valve gear adjusting directions at the Roundhouse web site and checked out some related threads from the Bednariks and Jay Kovac. The slide valve on the engineer's side was not centered between the two ports; so, I adjusted that. It ran really well in reverse on rollers, but a bit stiffly forward. With a little more examination, I discovered that the slide valve on the engineer's side was only moving about 0.080" while the one on the other side was moving about 0.120" which meant that the cylinder ports on the engineer's side were not fully uncoving. Once I adjusted the return crank, the amount of motion was equal. And it seemed to run well on rollers. Today I took it out and put it on the track and it runs very smoothly in either direction and it takes far less throttle to maintain speed. Today's test was fairly brief; but, tomorrow I'll be running at Larry Green's layout and will try to really wring int out. Llyn

Llyn Rice Cornwall, Vermont *Vermont Scenic Railway*

Kovacjr

1st Class Member
Lakewood NJ
Foreman

Foreman
Posts:213

05/12/2008 7:28 PM
I also just retimed my k28 and the easiest way was with a protractor set to 36 deg and lined it up with the main rods at TDC. Wirked almost perfect the first time. Not just to figure out my other issues with my changes to the valve.

Jason Kovac Lakewood, NJ

Charles

1st Class Member
Foreman

Foreman
Posts:469

05/13/2008 3:33 PM
Llyn Add your name the that list of references as to "fixin" steam! Good job.

Happy Trails on the Rails Charles SA #614 http://cebednarik.googlepages.com/home

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