reversing lever notch spacing

[SteveM]

Is there any rule, rhyme, reason, pattern, or sanity to the spacing of the notches on the reversing lever stand?

I realize there has to be one at each end of the travel, but what about in between?

And is there a rule about where the ends should be?

Steve

[Marty_Knox]

I can answer your last question first. The ends should be where you get the designed full gear valve travel. For the Allen locomotives, that is 5/8". So your full forward notch should be cut where you measure the valve traveling .625", same for the reverse. Baldwin practice was to put a stop so the engineer couldn't use more than the designed full gear. Another thing to note is that the die blocks are not all the way at the end of the link in this position.
Mid-gear should be where the valve is only traveling 2 times the lap and lead. The design condition for the Allen locomotives is 1/8" lap, no lead, so mid-gear is where you have 1/4" valve travel.

[daves1459]

I can answer your last question first. The ends should be where you get the designed full gear valve travel. For the Allen locomotives, that is 5/8". So your full forward notch should be cut where you measure the valve traveling .625", same for the reverse. Baldwin practice was to put a stop so the engineer couldn't use more than the designed full gear. Another thing to note is that the die blocks are not all the way at the end of the link in this position.
Mid-gear should be where the valve is only traveling 2 times the lap and lead. The design condition for the Allen locomotives is 1/8" lap, no lead, so mid-gear is where you have 1/4" valve travel.

I'd like to reinforce Marty's "... thing to note is the die blocks are not all the way at the end of the link...". If the die block bottoms out in the end of the link slot it jams up the linkage through the lifting shaft, reach rod, and all the way back to the reverse lever. So for each wheel revolution per side the link block jams up the linkage twice. The end result is over time the "jams" beat the valve gear to death including increased load on the eccentrics and eccentric rods. . I possess a loco that the previous builder did allow the block to jam in the link slot causing me to have to over size ream all of the pivot pin holes and make new pins. Also all of the dowel pins in the lifting shaft lever had to be replaced and the reverse quadrant slot engaging key replaced.

[jcbrock]

There are a lot of notches on larger locomotives because you don't really know where you are going to want to be as it depends on train weight and track profile, you feel what's right in the situation and leave the bar in that notch (adjusting as the track profile changes). Also, the center of the stand is not necessarily where the gear is centered, you may be a notch or two off that. For smaller scale live steam it is not that critical. I could get by with one reverse notch in the corner, one where the gear is centered, and two or three forward notches plus the forward corner. It just doesn't make that much difference in my experience, likely due to the small length of valve travel.

[ChuckHackett-844]

I think it will vary by locomotive. I would start with one at each extreme (fwd/rev) and one at the "actual" neutral (centered valve, no movement) which, as someone pointed out might not be in the exact center of the lever movement.

I would then run the locomotive and use clamps/whatever to hold the lever in other fwd positions to find the best "full" notched up position and a mid-notch position (1/2 way between corner and full up).

On my LE Old Northern the different positions makes a big difference but I know people who only use fwd/0/rev.

BTW I wouldn't bother with more than full reverse unless you plan on traveling long distances in that direction

[ChuckHackett-844]

Oh ... and you can always add notches but it's hard take them out or move them

[SteveM]

I'm beginning to realize how little I know.

I should have mentioned that the valve gear is Baker, so no die block

OK, as a steam novice, I have to ask: what's the definition of "corner"?

The ends should be where you get the designed full gear valve travel.... Mid-gear should be where the valve is only traveling 2 times the lap and lead. The design condition for the Allen locomotives is 1/8" lap, no lead, so mid-gear is where you have 1/4" valve travel.

I guess I also need some definitions of lap and lead and how to measure them.

As far as "full gear valve travel", am I looking for the setting where the valve travel is the maximum? Does it get less if you go past that, or does it just not get any more?

Steve

[ChuckHackett-844]

"In the corner" is full fwd or full reverse, i.e.: the limits of travel.

Take care to have physical stops (not just the notches) at the limits so as not to damage the valve gear with overtravel as has been mentioned.

[SP&S700]

let me quote from a book I really dont like its diagrams moving from direct to indirect valve motion then showing out side admission slide valves etc any way this is how they describe lap and lead.
" A steam engine cannot be operated economically unless provision is made for moving the piston by expansive force of steam and this can be done only by giving the valve steam lap. The steam lap makes the valve wider than the steam port and, therefore ,introduces and interval between cut-off and release, instead of these valve events occurring simultaneously as in Fig 1 (a} and {b}

Enough I fired up the office computer and scanner and will attach. I,m not trying to be a know it all. I hope some of the other folks here can simplify this for you. This is just to start the back and forth as I think Bill S once said. Hope the attachments come out ok.
Clint

[SP&S700]

Steve
You say your working on Baker valve gear, well my hat is off to you because baker is usually found on the later steam engines like Berks and such, it is considered better than Walschaert by many.
Looking in my favorite book again, I find its explanation about lap and lead is better under the Baker Section. So I shall attach some not so great pics, hope they are readable.
So here is a short quote from the famed book! page 8 and 9. on Baker Gear

"Owing to the back pressure that would develop on the return stroke of the piston, a steam engine cannot be operated at high speed unless provision is made to begin the exhausting of the steam before the piston completes its previous stroke. Neither can an engine be operated with economy unless provision is made for the moving the piston by the expansive force of steam. Both of these conditions can be met by giving the valve steam lap. Steam lap not only causes an earlier release of the steam, but it also introduces and interval between the valve events, cut-off and release, instead of these events occurring simultaneously as with a valve with no lap. During this interval the steam expands in the cylinder and moves the piston."
Hope this is of some help

[RET]

Hi,

Just to make things more interesting, no matter what type of valve gear you are using, if you get the gear set up perfectly, the locomotive will run in mid-gear on level track if you are over about 5 miles an hour (for 7 1/4"). The locomotive will have no power to speak of, but it will run in either direction. It does this because the valves open briefly at top and bottom dead center because of lap and lead.

I know because I've driven a 7 1/4" gauge 4-4-0 (Harry Allin's Centennial) that does this.

Just my 5 cents (2 cents isn't worth anything these days).

Richard Trounce.

[Bob Chamberlain]

hey steve, I just happen to have a complete reverse quad machined and ready for install from the sixties made by little engines looks very nice I am building an atlantic and installed a Moore power reverse so will not be using it just a thought for you. PM me if your interested if not good luck with your project.