Balancing engine

[seal killer]

All--

I would like to balance a single cylinder, single acting spool valve engine I built. My intention is to balance the flywheel to the engine. I've never done this before. To achieve balance, do you remove as much weight from the flywheel as the piston, connecting rod and crank pin weigh?




--Bill

[david griner]

This might be of interest to you:

The Balancing of Engines, W.E. Dalby :

https://books.google.com/books?id=Bk9DA ... by&f=false


Dave

[Fred_V]

Simply put you weigh the big end of the main rod and the ecc. rod big end. Remove that amount of weight from the flywheel. The eccentric will be a problem as it is not in line with the crankpin so you will have to use some judgement.

Set the crank/flywheel shaft on knife edges and add the weight of the above mentioned parts to the crankpin and ecc. and start removing flywheel weight until the assembly rolls on the knife edges without rolling back to find the heavy spot. You can also add weight opposite the crankpin to balance it if you remove too much. You should be able to get pretty close this way.

[seal killer]

Dave and Fred--

Dave, thanks for the link to the book.

Fred, thank you for the explanation. It will get me started.

--Bill

[ken572]

This might be of interest to you:

The Balancing of Engines, W.E. Dalby :

https://books.google.com/books?id=Bk9DA ... by&f=false


Dave

Hello Dave
Thanks for the GREAT FIND

That book can be helpful for anything

that rotates.

Ken.

[steamin10]

Ken, Seal, and Fred: I am going to jump into the abyss and say that for many practical reasons, you will never balance that engine.

First, the book mentioned is a leading treatise on such arts as balancing rotating machinery of locomotive, marine, and industrial size, for early 1900, and is the culmination of direct observations and work of the day. It really speaks to a nasty problem.

Without getting into a lot of rhetoric, from this non papered engineer, you must understand that static balance, and dynamic balance, are two animals forever joined in operation. The numbers change with the motions made, with acceleration, mass, speed, and angles to generate forces for drive and waste of energy that will express itself in unwanted vibrations.

In modern design, piston and reciprocating anything, can be balanced near perfectly for a narrow band of shaft speed. Above and below that perfect number, balance is nearly a fantasy. The more complex the assembly, the more complex the equations for vibration cancellation.

In the early days of steam in particular, (an 1899 work is cited early in the read, and I did not read it all) engines were built HEAVY, with stout and massive engine beds. Shaft speeds were low, and things moved on. Railroads in particular, had the problem of pounding bearings in the motions, (rods) and wheels lifting and pounding the rails for the need for speed. (Dynamics).

So I field the argument, that such an engine can only get 'close' in the old sense, without perfection, which is the historic copy of what was.

Nice looking engine, Seal.

[seal killer]

steamin10--

Although I did not have anywhere near the expertise to arrive at your conclusions, this is what I decided to do: The engine operates very smoothly at low to "moderate" speeds. I will crank it up into the area wherein it first starts vibrating as I would not wish. Then I will take material off the flywheel until that vibration disappears and call it good from low speed through that speed.

What do you think?

--Bill

[Fred_V]

Good plan. As I said, you can get close. There is a max piston speed in feet per min. and i think our locos run at a max of 300+ RPM. can't remember for sure.

[NP317]

Good discussion of static vs dynamic balancing.

When Jack Anderson and I (plus two other crew members) rebuilt Hillcrest Lumber Company Climax #10 (1981 at Mt. Rainier Scenic Railroad) it arrived with counterweights welded to the two crank discs.

We learned from Hillcrest's president that shortly after factory delivery to Vancouver Island, BC, they had replaced the Climax factory sliding counter weights with those welded cws, due to maintenance issues in the woods. I can believe that.

The result was a locomotive that ran smoothly from 0-8 mph, and from 12-15 mph. Unfortunately, from 8-12 mph it hit harmonic frequency with the springs in the trucks and bucked violently up and down! (That explains why we had to replace ALL the locomotive's springs, and weld up cracks in the truck frames.) We thereafter referred to that as "hump speed!" Jack had to wear a kidney belt when firing and I stood all day when engineering #10. Still, this was the most fun I've ever had in my life, working 14 hour days!!!

Of course the speed limit on much of that old rail line was ... you guessed it ... 10 mph!! I chose to usually run #10 just above hump speed...\FAST for a Climax locomotive! We also chose to keep the cab doors closed, after the tool box bounced out the fireman's side and spewed its contents all over the right of way! The passengers got a kick out of that stop in the woods!

After I left MRSRR, Jack torched off portions of those counter weights and ended up averaging the "unbalance" over the locomotive's speed range. It was no longer "smooth" at any specific speed range, but produced small vertical vibrations at all speeds. It remains that way today.

And that's my story about dynamic balance issues. So give me a Heisler to engineer, any day!
~RN

[steamin10]

Ya, as the previous story shows, consider ADDING weight to the flywheel for the desired effect. They did this method on rod engines with the plates on the high stepping 4-4-0 Americans, and with crescent shapes on later and much larger engines for the rails, with Box-poc designs and others, meant to trade static for dynamic values.

But you get my meaning, no true answer, just close.

[ken572]

(ALL)

I forgot I also had these, they might be of
interest, for your Balancing Needs.
- - - - - -
Experiments on engine balancing: with a special model 1907 (40p)
-
https://archive.org/details/experimentsoneng00bart
or
https://archive.org/download/experiment ... 00bart.pdf
- - - - - -
Graphic Methods of Engine Design: 1897 (230p)
Including a Graphical Treatment of the Balancing Engines
-
https://archive.org/details/graphicmethodse00barkgoog
or
https://archive.org/download/graphicmet ... rkgoog.pdf
- - - - - -

Ken.

[seal killer]

steamin10 and All--

Re: Adding weight instead of subtracting weight.

I just did the math for my little aluminum flywheel. The piston and connecting rod combination weigh 0.044lbs. The height of the rim of the flywheel is 1/2" and the flywheel is 1/2" wide. My plan was to drill enough 3/8" holes in the rim to approximate the weight of the piston/rod combo. But, that would be 11 holes. With 0.050" between them, those 11 holes would be spread over about 4 5/8" of the 9.4" circumference of the flywheel. Does the weight removed need to be concentrated in a smaller area or is it sufficient that it simply be on the "other side" of the weight of the piston/rod?

Adding steel weight in a smaller area might make more sense, but I don't see a way to do that easily with my flywheel. (Hmmmm. I COULD drill and tap three holes in the rim and screw in some threaded steel weights . . .)

--Bill