Weight Distribution Question on a Live Steam Locomotive

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Carrdo
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Weight Distribution Question on a Live Steam Locomotive

Post by Carrdo » Fri Nov 09, 2018 3:21 pm

Does anyone have a practical method for determining this?

I really would like to be able to determine the weight distribution on the 3/4" scale Hudsons and Northern here.

I suspect that 100% of the locomotive dead weight is on the drivers only and that the leading and trailing trucks are just going along for the ride but I can't prove it. I could be wrong.

On full size, they use electro/mechanical load cells which will record real time weights as the locomotive and cars pass over.

I tried using simple bathroom scales but they don't work - no meaningful results obtained.

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Bill Shields
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Re: Weight Distribution Question on a Live Steam Locomotive

Post by Bill Shields » Fri Nov 09, 2018 5:30 pm

put a lifting fork under each wheel that is a 'teeter totter' so that you push DOWN to lift the wheel.

arrange this so that the pivot is a fixed distance from the where the fork lifts the wheel....and you have a fixed position to:

add weight to the 'push down' end of the teeter totter until the wheel JUST lifts from the table top.

I guess that you could do this on the edge of a table and PULL DOWN with some sort of electronic 'fish scale' that is attached at a known point.

repeat for each wheel....or maybe just one side of each axle and X 2

do the math...

add a 'fudge factor'...because there is a lot of 'stiction' in leaf springs...

theoretically if you just 'weigh' the drivers you can 'assume' that the remaining weight is on the non-drivers...but then you need to weigh the entire loco.
Too many things going on to bother listing them.

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Carrdo
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Re: Weight Distribution Question on a Live Steam Locomotive

Post by Carrdo » Fri Nov 09, 2018 6:10 pm

Hi Bill,

I can tell you the dead weight of the Langworthy Hudson (as it is today) for example:

Lead truck - 5 lbs
Trailing truck - 10 lbs
Complete engine weight (minus the leading and trailing trucks) - 108 lbs
Total engine weight (with all of the details some of which I have yet to add) - 125-130 lbs

But what happens when it all goes back together? Does the weight redistribute among the leading truck, the drivers and the trailing truck? Richard says yes but if I misquoted him again, he can chime in and correct me.

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Bill Shields
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Re: Weight Distribution Question on a Live Steam Locomotive

Post by Bill Shields » Fri Nov 09, 2018 7:50 pm

The only way to tell is as suggested since we really do not know how the equalization settles out
Too many things going on to bother listing them.

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pat1027
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Re: Weight Distribution Question on a Live Steam Locomotive

Post by pat1027 » Fri Nov 09, 2018 9:30 pm

Eloquent in its simplicity.

https://youtu.be/I4q1b5KY7P0

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David Powell
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Re: Weight Distribution Question on a Live Steam Locomotive

Post by David Powell » Sat Nov 10, 2018 11:15 am

You do NOT need to know the actual weight, what you need to know is" Will the loco run safely on the track you are running on" . With the engine in steam on the track stand straddling the track and put one index finger between the spokes of the carrying wheels on the front axle and lift about 1/8" if you feel equal weight on each, and that weight is equal to or a bit more than what you figure the truck or bogie weighs then move on to the next axle and repeat. IF they all work out at that, put a few shovelsful on the fire and gently run around the track. If they dont then stop, make adjustments to the adjusters or springs on the driving axles, maybe you have to go home, or maybe just a bit of wrenching will do that, and try again. If you cannot lift the bogie or truck wheels at least 1/8 " without lifting driving wheels then it is lilely you will suffer lots of derailments. Most tracks are FAR from level and all the wheels need to be able to follow the humps and hollows. Traction engines are more fun and do not need rails. regards David Powell

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Builder01
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Re: Weight Distribution Question on a Live Steam Locomotive

Post by Builder01 » Sat Nov 10, 2018 11:50 am

David Powell wrote:
Sat Nov 10, 2018 11:15 am
Traction engines are more fun and do not need rails. regards David Powell
Why the shot?

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David Powell
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Re: Weight Distribution Question on a Live Steam Locomotive

Post by David Powell » Sat Nov 10, 2018 12:51 pm

In 30 odd years of running model railway engines, mine and other peoples, I suffered a number of derailments and dealt with a few engines which would not consistently stay on tracks, or which would run well on one club track and derail on another. I have a number of model traction engines of 1 1/2" and 2" scale, I have a drivers seat and a flat trailer for them. So far I have neither fallen off the trailers nor tipped any passengers off. In these days where liability is a concern i feel the traction engines much less likely to create problems. regards David Powell.

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Builder01
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Re: Weight Distribution Question on a Live Steam Locomotive

Post by Builder01 » Sat Nov 10, 2018 3:23 pm

So the reason for the shot has been your bad experience. Interesting.

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David Powell
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Re: Weight Distribution Question on a Live Steam Locomotive

Post by David Powell » Sat Nov 10, 2018 5:12 pm

The experiences have not been " bad", I have never hurt anyone else with a model steamer .Indeed I have not had more than a scratch or minor burn, or fright myself. My partner and I have 6 workable locos ranging from a 3 1/2" Tich to a 7 1/4" Dart all of which get occasional runs on local tracks.Nowadays I do not pull passengers other than family or club members. The traction engines and steam roller get steamed frequently, indeed seldom does a summers day go by that I do not have steam up,they get run in our garden and on our driveway and at the club sites. I simply have more fun, more freedom and less worry than when driving our railway engines. Regards David Powell.

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Re: Weight Distribution Question on a Live Steam Locomotive

Post by Wolfgang » Sun Nov 11, 2018 3:55 pm

Carrdo wrote:
Fri Nov 09, 2018 3:21 pm
Does anyone have a practical method for determining this?

I really would like to be able to determine the weight distribution on the 3/4" scale Hudsons and Northern here.

I suspect that 100% of the locomotive dead weight is on the drivers only and that the leading and trailing trucks are just going along for the ride but I can't prove it. I could be wrong.

On full size, they use electro/mechanical load cells which will record real time weights as the locomotive and cars pass over.

I tried using simple bathroom scales but they don't work - no meaningful results obtained.
Hi Don!

When I first steamed my CPR Hudson, ol' #2888, I swear it would derail with a blade of grass on the track! This happened so easily and often that it destroyed one of the truck wheels...

Thinking about this problem and debating it with a good friend, I decided to load the front truck with 10% of the locomotive all-up weight, 10% being 14 lbs. Further, I decided that the truck centering force would also be 14 lbs... The latter decision was not quite as arbitrary as the first; wheel geometry being what it is, a centering force of 14 lbs would not lift the wheel over the flange with a vertical force of 14 lbs holding it down.

Springing was fabricated plus the various bits and pieces to hold things in place.

Since then my son Ian and I have steamed #2888 on the MLS track at Les Cedres, and the GHLS track in Hamilton; I am pleased to state that since the implementation of these improvements we NEVER had another locomotive derailment!

It is important to remember that model RR tracks are much more uneven (scalewise) that full size tracks, yet we expect to traverse the model track at much higher speeds than full-size practice. At least I am inclined to do this with the way ahead clear. w

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