Experiment in subtle weight balance in a steam loco

[mmagliaro]

That's a hunka hunka melted lead!  Now... if it were only tungsten

My W-5 weights, at about 125g, is only the engine.  Including the tender, I am at about 168g.   I can't
be sure, but I could have sworn I saw  my wooden trestle dip last night as the engine rolled over it 

Sadly, I continued on with the project to do the mounting of the boiler permanently to the chassis.
Those of you who have built GHQ kits know that they generally do this by tapping some holes in the frame,
screwing a small brass plate to the frame, then tapping a threaded hole in that plate, and finally running
a screw down through the dome into that threaded plate.   I did all that fine.  but the plate is right where I have
that big home-made tungsten weight to replace the Kato one, right over the drivers.   I refashioned the
whole thing to accomodate the mounting plate and screw, but I made it out of lead because that's so much easier to
shape and cut.  When all was said and done and the boiler was screwed on, that cost me 5g of weight over the drivers.

It's still much heavier than it was a week ago, when it could still pull 55 cars, but it can't do it anymore.  I
have clearly disturbed the balance.   Sure enough, if I put 6g of weight right over the center, the pulling power
returns.  So today, I am using diamond cutoff disks and cobalt drill bits to shape a tungsten plate to go back in
there in place of the lead replacement.  It cuts, but man, tungsten is hard stuff.

[victor miranda]

ah  Lemosteam,

next time you cast a k4 chassis  weight,
dust the mold with talcum powder.   you will reduce the bubbles.

forumers,
when this thread started I was pretty sure it was going to head into
how to improve pulling in general.

I am a big believer in traction tires.
and when they don't work, it means the tire is gone.

when adding weight does not get more pull....
balance is top on the list of things to investigate.

among the things that can affect balance is the tender/drawbar
lifting the back of the loco.   going into the start and end of a grade
are exactly where this can be the most notable.

cheers
victor

[peteski]

I am a big believer in traction tires.
and when they don't work, it means the tire is gone.

among the things that can affect balance is the tender/drawbar
lifting the back of the loco.   
victor

I also think that in N scale traction tires are necessary evil.

But as far as the drawbar goes, depending on its design and placement (if it is high enough)  it can also exerting extra pressure on the rear driver (and lifting the front of the loco).  Exactly opposite to what you stated.

[peteski]

Since modifying posts is now forbidden, I want to add this to my last post:

At least that is what "Peteski's logic" from the A-board dictates. 

[victor miranda]

I also think that in N scale traction tires are necessary evil.

But as far as the drawbar goes, depending on its design and placement (if it is high enough)  it can also exerting extra pressure on the rear driver (and lifting the front of the loco).  Exactly opposite to what you stated.

while this is true....
it usually results in more traction... which is what we want.

Lifting the traction tire off the rails is THE problem.

cheers
victor

[mmagliaro]

ah  Lemosteam,

next time you cast a k4 chassis  weight,
dust the mold with talcum powder.   you will reduce the bubbles.

forumers,
when this thread started I was pretty sure it was going to head into
how to improve pulling in general.

I am a big believer in traction tires.
and when they don't work, it means the tire is gone.

when adding weight does not get more pull....
balance is top on the list of things to investigate.

among the things that can affect balance is the tender/drawbar
lifting the back of the loco.   going into the start and end of a grade
are exactly where this can be the most notable.

cheers
victor

A very good list, Victor, and I agree with it.  By the way, I did find that the spring wires from the Kato drawbar that rub on the backs of the truck pickup fingers on the front tender truck cause considerable lift of the rear of the Mikado. 
There is a delicate balance between having them press on the insides of the truck fingers enough to maintain reliable contact, but not push so hard as to restrict the up/down "float" of the rear of the engine.  In my case,
I had soldered/hard-wired around those anyway, so I just removed them.  When I did, the engine pulled a lot more cars (this was weeks ago), and by "a lot" I mean at least 10.

[up1950s]

Since modifying posts is now forbidden, I want to add this to my last post:

Huh , when did that happen , I thought we could but after a period of time <24 hrs or so the option is disabled by the written code scribed by the honcho code writer .


I have made some changes to this post , this sentence being one of them .

So now the question is of times up , too late , live with it , go tell your Mama .

[Lemosteam]

ah  Lemosteam,

next time you cast a k4 chassis  weight,
dust the mold with talcum powder.   you will reduce the bubbles.

Unfortunately, the bubbles were on the master!  The mold was just a test to see if it would even work, but it did...

[victor miranda]

I am laughing from this thread.

I guess I have to start with I quoted peteski's post and maybe that 'locked' it?

I have to also state I was in a hurry when I replied.
So I'd like to explain a bit that pressing the back of the loco down
is indeed a balance issue. It is entirely possible for a loco to lose traction from that condition.
it is out of the ordinary. I have to state the only time I recall having the problem,
I did not notice the if there was a  traction problem.
I found the problem because the tender would derail in reverse with a curve and pushing few cars.

it is a balance issue and when you are sorting out a problem,
it is one to attend as you look for causes.

and last but not least
it never crossed my mind that
the bubbles are:
a feature not a bug.

cheers
victor

[peteski]

The ability to edit posts was disabled at least a day ago and must have just been restored between when I tried to edit my post above and when up1950s was able to edit.  As shown in thread https://www.therailwire.net/forum/index.php?topic=34004.0  the fix was supposed to happen last night but must have been delayed to some time between 3:00 pm and 4:23 PM EDT.   It wasn't you Victor.