Joe,
Is it ok if I take your word for it?
John
Cube root would give you scale weight, and you are right, I doubt that many of the small electric motors and plastic gears could handle that.
2.866 pounds per axle. Well, that explains why my 2-4-2 is such a poor puller. Even after adding a pound of weight, I know she doesn’t come in anywhere close to 5.732 pounds.
An engineering friend told me you can figure on the wheels slipping when the tractive effort is roughly .22 times the weight on the drivers. Varies a bit by what the wheels and rails are made of and what’s between them. At 1.3KG per axle, my slightly overweight mallet is still a hair light. Well, about 4 pounds light. She has pulled dead dash 9s.
this makes me want to get mine running. I have to weigh it again but I believe I have it a shade over 4 pounds. with suggestions here it might need to weigh twice that. (http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-cry.gif)will be a challenge getting more in there. But I won’t do it until after i do some pulling. I don’t expect it to pull more than 4-5 cars at a time as that is prototypical.
Whoa!
We are not pulling scale weights either.
The biggest influence will be the drag of your cars wheels. Check for burrs and lube.
Add cars and see how it starts and stops, you’ll see where it moves easily and where it struggles.
I suggest bags of shot hung over the loco to temporarily add /subtract weights while testing and looking for a happy medium.
No wheel slip at start and no pushing the engine during braking. Too much weight and you’ll treat it like a stump puller when the gearing supports easy running…
Doubling the hill, was a common experience when the yard boss would over load your engine… break it in the middle, leave the conductor protecting the rear of the left half, while the loco takes half up the hill, parks it in a siding and comes back for the rest.
Happy Rails
John
Doubling the hill??? That sounds like real work! The roundy-rounders will be upset. (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-tongue-out.gif)(http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-laughing.gif)(http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-innocent.gif)
Steve Featherkile said:
Doubling the hill??? That sounds like real work! The roundy-rounders will be upset. (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-tongue-out.gif)(http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-laughing.gif)(http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-innocent.gif)
Fortunately roundy-rounders generally have the same disdain for grades as they do switching! (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-surprised.gif)So things ought to work out fine for them. (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)
Great topic, I want to go home and weigh my engines now to see where they shake out. I’m pretty sure my EBT 12 will be about 10LBS per axle!
Did driver size matter when “the group” came up with the “3 pound per” rule?
Did driver size matter when “the group” came up with the “3 pound per” rule?
i do not remember having read about that.
what was mentioned, were the not powered axles. consense was, to count them in, because part of the weight would be carried by them.
Randy Lehrian Jr. said:
Fortunately roundy-rounders generally have the same disdain for grades as they do switching! (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-surprised.gif)So things ought to work out fine for them. (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)
Hey now! (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-surprised.gif)I am a roundy rounder. You know that. I also have a constant 2.58% grade on my mainline. And that you know too. So, are you saying that I am just different then the general roundy rounder? (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-frown.gif)
Ok. (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-laughing.gif)I can accept that.(http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)
Thanks Korm, not sure I agree with that logic though. If an axle was unpowered, adding weight to it would do nothing to add tractive effort.
I knew you'd chime in on that David! And if memory serves, you often seem to be the exception to generalizations I make. You truly are a rare bird! 
Randy Lehrian Jr. said:
Thanks Korm, not sure I agree with that logic though. If an axle was unpowered, adding weight to it would do nothing to add tractive effort.
Randy,
On a steam engine, all wheels are powered by means of the rods. Whether a full size or a model steam loco all the wheels that are mechanically turned add to tractive effort if they are on the rails. (http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)
Joe Zullo said:
Randy Lehrian Jr. said:
Thanks Korm, not sure I agree with that logic though. If an axle was unpowered, adding weight to it would do nothing to add tractive effort.
Randy,
On a steam engine, all wheels are powered by means of the rods. Whether a full size or a model steam loco all the wheels that are mechanically turned add to tractive effort if they are on the rails. (http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)
No Joe,
Not all wheels on a steam locomotive are powered by rods. Now I am sure you meant to say all drivers are powered by rods. The pilot and trailing wheels most certainly are not powered. I believe Korm was referring to those such wheels. There would be little to no point in my opinion to weight the pilot or trailing wheels of a locomotive, prototypical or model, beyond what is necessary to keep them in positive contact with the rails for the purpose of keeping the locomotive on the tracks in a corner. In my minds eye weighting a locomotive evenly over all wheels including those not powered would defeat the purpose of the weight in the first place which is to provide tractive effort. If you distribute weight to all wheels evenly then you are actually robbing the wheels providing traction. This would in essence be causing a double negative, less traction to weight ratio and also requiring the locomotive to pull more weight without the benefits of the weight thereby again reducing it efficiency. I would say that on the real deal and on the model most of the weight needs to be over the drivers and only that amount of weight required to make the non-powered wheels should be applied to keep them in positive contact. I am no engineer but this just makes common sense.
Brings up another question for another post maybe but what is the point of the trailing wheels on a loco. If the pilot leads the loco into a corner what is the purpose of the trailing truck. The only thing I can think of is the fire box and boiler extends so far behind the drivers that it weight must be supported. But if your creating such a large power plant why not add drivers?
Graeme Price said:
A question about what would the weight of an 0-4-0 steam loco should be.
I have an LGB Stainz loco that weighs about 2Kg but an LGB “Shorty” loco that weights in at a rail crushing 3.5Kg.
Both are battery powered with the same electronics and battery capacity, but every time I run them the “Shorty” runs out of power first I ran them with identical wagons for the purpose of testing.
I am assuming that the extra 1.5Kg is causing the motor to draw to much out of the battery and am considering removing some more weight (I took some out when I converted to battery power).
What is the average weight that others use on small shunting type locos?
I’d say they were both too heavy. My small shunters are around 1kg.
Thanks Devon, That was exactly my point, and the way that I interpreted what Korm said.
You are also correct on your secondary question about trailing trucks. Indeed some of the fire box weight and the weight of the cab need supporting. Adding more drivers wasn’t possible for a few reasons. Fire boxes got wider as designs evolved allowing for more grate area to pull in fresh air. Because of this the could no longer fit between the drivers or between a spaced out set of drivers as in an early American or Ten wheeler. Why not just add another set of drivers spaced out for behind the boiler on the aforementioned early types? Well by this point locos were already getting quite long so on a something- 4 - something adding a fifth set of drivers back there would have made an extremely long ridged wheel base and limit the ability of the engine to go around curves.
Randy,
I took Korm’s method to mean drivers, not pilot or trailing wheels. I thought he had said that. Sorry if it confused you.(http://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-cry.gif)
well, let me try to confuse you more:
let us take the big hauler as example.
i gave mine three times 1.3 kg weight. and it ran good - untill split gears made for forced retirement. (before, without additional weight, it could not even haul its own tender up the 6% grade)
the two axles of the ponytruck (the “4” in 4-6-0) do not carry any/much of the loco weight. so, forget them. (and weight them individually against derailments)
the drivers (“6” in 4-6-0) all take part of the locos weight. if powered, or not. so to have 1.3 kg upon any powered axle, every axle that is fixed to the chassis, has to be counted in.
sure, a loco, with one or more not powered axle(s) never can be as good at towing, as a loco with powered axles only.
i think, that is the secret, why our smallest locos often are our best workhorses.
like the Stainz, the Köf etc. - axles rigid, both powered, all weight used for traction.
(and that is, why i use for my layout with 6% grades only stainzes plus powered tenders.
a 0-8-0 loco with all axles powered would have one or more axles hanging in midair, everywhere the track angles up or down.
0-4-0 loco plus 0-4-0 tender always have all (powered) axles pressing on the rails.)
Hey Joe, It’s no thing. (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-wink.gif)And Devon did the hard part typing it all so it could only be interpreted one way. (http://largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-smile.gif)
I think the dynamics of steam and diesel cassis design definitely have different effects on how the weight and position of it translate in to tractive effort.
Randy yes, Diesels are different, but the ideal weight per axle is probably about the same.
As for the trailing trucks, yes they were added to support the larger fireboxes. The locomotive designers saw that the weight there was “dead”, it wasn’t adding to the tractive force, and was essentially trailing weight. Weight like a freight car. So there were attempts to power trailing trucks, with small steam motors, to add to the tractive force when starting out, or at slow speeds. The added power wasn’t worth the added weight, complexity, and maintenance of the booster motors, so the idea was eventually dropped.
from Wikipedia…
Korm Kormsen said:(before, without additional weight, it could not even haul its own tender up the 6% grade)
Actually, that is probably right in line with reality.
Let’s see here, according to reprint of Porter locomotive catalog, we’ll take a 92,000 pound 2-6-0 of 48 inch drivers and 16x24 cylinders, weight on drivers 79,000 pounds, with 52,000 pound tender, both weights in working order. Locomotive was order-able with telegraph/telegram code word “HATEAR”
Rated to pull 2,770 tons on the level. On a 1.5% grade it could pull only 37 percent of that flat land weight, 1,045 tons. On a 3% grade that dropped to 205 tons.