A fresh look at engine balancing at home.

[xyzer]

38
The 2 6/1's I dynamically balanced were set up for balancing 55% of the reciprocating mass from India. Just a tad more than half of the piston and upper rod assembly. After several tries we found to get rid of the pounding(bolted down) or hopping (not bolted down) and just before it became a slider we were at 67%. You will probably end up adding weight to the area of the counter balance. And it will probably be more than you might suspect.

My first try........the strips under the c clamp is lead.

[38ac]

 

[fuelfarmer]

Thanks for posting this topic. This is killing me. I am still tempted to take the lazy way out on an 8/1 kit, but maybe the right thing to do is try to do it right. A hobby, by it's nature, should take way more of your time than you first thought........

[veggie]

How about this method ?

http://www.youtube.com/watch?v=yfecDTfU1tQ&feature=related

veggie

[carlb23]

veggie,

I used the same method but instead of drilling my flywheel i used stick on lead wheel weights 180 degrees from where my marks were.

[38ac]

 

[Quinnf]

Hey Dave,

When you say 67% of the reciprocating weight, do you mean that's the combined weight of the two counterweights on the flywheel rim?  It's been a while . . ..[edit:  here's the exchange  http://listerengine.com/smf/index.php?topic=1431.msg19164#msg19164, I think I can figure it out.  It's been a few years!

Thanks,

Quinn

[xyzer]

Hey Dave,
When you say 67% of the reciprocating weight, do you mean that's the combined weight of the two counterweights on the flywheel rim?  It's been a while . . ..[edit:  here's the exchange  http://listerengine.com/smf/index.php?topic=1431.msg19164#msg19164, I think I can figure it out.  It's been a few years!
Thanks,
Quinn

Quinn,
The 67% is arrived from the total weight of the piston assembly, and the weight of the little end only of the rod. A bobweight of that calculated weight is put on the rod journal like my post above shows and then the flywheels are statically balanced so there is no heavy spot. My first try at this reviled you need to use 1/2 of the 65% and only balance one flywheel at a time! I did one dynamically and they can do both flywheels mounted. Doing both wheels statically you don't know which wheel needs the weight. When I finished mine up I was shooting for 65% but always had to tune it with a tad more weight and 67% is probably where it ended up. Standard balance on lots of normal engines is at around 55%.  A stock Listeroid is also at around 55% and that is why they pound. Not enough of the cast iron piston is compensated for. The higher % balances the pistons reciprocating mass more. The further you go past there 67% it will start to become a slider. If you went to 100% it would become an extreme slider!
Dave

[Quinnf]

Hey Dave,

Exactly 5 years ago to the day we were discussing this same subject at http://listerengine.com/smf/index.php?topic=1431.msg19154#msg19154
Was reading through it and enjoying the exchange between Bob and GuyFawkes, that old blowhard.  I really miss him.  Much as I hate to admit it, I learned a lot from his rants.

Anyway, was thinking about balancing again.  And I read that you wrote:


   
Re: engine mounting v 4.0
« Reply #104 on: December 29, 2006, 03:09:39 am »
   Reply with quote
Quinn,
Yes it is nice to see some other numbers. I should have posted my Vidhata #'s also but didn't want to confuse the issue.
Check your addition... I added yours several times and could not get the same numbers. ?!!!?

                 VIDHATA

Small end of Rod         1216   grams =  2.680#
Piston assembly           4025   grams =  8.873#
Big end of Rod            2742   grams =  6.045#
-----------------------------------------------------------
Total                         7983   grams = 17.599#
Bobweight @ 65%      6149   grams = 13.556#  
          


            POWER SOLUTIONS Kit

Small end of Rod          1147   grams=   2.529#
Piston assembly            4024   grams=   8.871#
Big end of Rod             2584   grams=   5.697#
-------------------------------------------------------------
Total                           7755   grams= 17.096#
Bobweight @ 65%        5945   grams= 13.106#            
                        

                       Quinns

Small end of Rod            1194   grams=   2.632#
Piston assembly              3840   grams=   8.465#
Big end of Rod               2819   grams=   6.214#
--------------------------------------------------------------
Total                            7853   grams=  17.312#     HuhHuh  I think I added it up 5 times same answer??!!
Bobweight @ 65%         6091   grams=  13.428#


avg assembly wt.           7864   grams=   17.335#
avg bobweight @ 65%   6062   grams=   13.363#

I am betting the differences in the assemblys will only be a small % in the balance factor another words my flywheels would run well on your engine. I do need to put my P/S wheels on the Vidhata to confirm that!


After I figured out you were measuring 65% of the reciprocating portion, not the whole enchilada we were in agreement with your numbers.  You should be able to calculate this easily.  It's a simple torque problem.  The torque imparted to the crankshaft by the bobweight at half the stroke length (5.5" / 2 = 2.75" radius) from crankshaft center must exactly balance the torque imparted in the other direction by the weight of the counterweights (2 of them) on the flywheels.  I measured that radius at 10" from the crankshaft.  That might be a little off, and the engine is 1100 miles away now and I won't be there until the middle of January so I can't measure it right now.


So the torque diagram would look like this:

                                    10"                                     2.75"
+----------------------------------------------------O-------------------+
1691g                                                          ^                     6149g


So that means that at a radius of 10" from the center of the crankshaft, 1691g will balance out the 6149g bobweight you placed on the crank pin which is centered 2.75" from the center of the crankshaft.

That means that each flywheel needs 1691g/2 = 846g of weight, or 28.9 ozs of weight.  That's a lot less than both Jack and I measured as the weight of the cast in weights on our flywheels.  As I recall Jack measured his at 47 and 48 ozs, while mine were 35 and 54 ozs.  or about 45 ozs average.  

Maybe the 10" radius is off, but if it is, it's not off by much.  My engine's at the wife's in Washington, so can't nip outside and check that radius at the moment.

I'm sure there's some bright individual with nothing to do on New Year's eve-eve but tell me where I'm off.  Any thoughts?

 

Quinn


 

[cgwymp]

How about this method ?

http://www.youtube.com/watch?v=yfecDTfU1tQ&feature=related

veggie

As usual Willem is (in my opinion) right on for the most part then he throws in something that is totally off the wall BS that screws uip the entire thought.

Interesting that he had several groups of holes spaced pretty widely around the flywheel. Looks like he was chasing the balance point, probably as he increased engine speed. I can't see where he accounted for the inertia of the engine's mass, so the apparent heavy spot lagged the true heavy spot...

[xyzer]

Quinn,
My how time flies! And you found all of those numbers we had! Reading my old post again even had me confused! For clarification 65% of piston assembly + 65% of little rod end + 100% of big rod end=6149gr.

 One thing the math does not account for is the weight of the offset rod journal hanging out there. I don't think it accounts for all of the difference. When you static balance you are balancing for that unknown also. Jack had a nice set of wheels to be that close. At least they were the same. Yours would be a real pain! I never weighed mine to see how much weight total weight was on one side. I need to do that someday. I do know I had to add weight to the cast weighted area to be balanced and from what I have observed so do most of the others. You even forced me to research a lever! I can't account for the major math discrepancy or something other than the rod journal weight is floating around out there. I'll borrow your closing...  "I'm sure there's some bright individual with nothing to do on New Year's eve-eve but tell me where I'm off.  Any thoughts?"
Dave

[xyzer]

Interesting that he had several groups of holes spaced pretty widely around the flywheel. Looks like he was chasing the balance point, probably as he increased engine speed. I can't see where he accounted for the inertia of the engine's mass, so the apparent heavy spot lagged the true heavy spot...

He was using the MrX method. A very good way to get it done.
I would not recommend drilling theses questionable flywheels just my opinion of course. I have, and found it to be a major pain and like in the video he ended up adding muffler clamps to the opposite side. I used clay inside of the rim to get a ballpark weight and area then replaced it with stick on truck weights inside of the rim. You don't have to pull off the flywheel and drill remount it and try again take it off and so on. With clay you just keep adding or moving clay. You get good practice starting the engine without removing the flywheels.

[cgwymp]

Interesting that he had several groups of holes spaced pretty widely around the flywheel. Looks like he was chasing the balance point, probably as he increased engine speed. I can't see where he accounted for the inertia of the engine's mass, so the apparent heavy spot lagged the true heavy spot...

He was using the MrX method. A very good way to get it done.
I would not recommend drilling theses questionable flywheels just my opinion of course. I have, and found it to be a major pain and like in the video he ended up adding muffler clamps to the opposite side. I used clay inside of the rim to get a ballpark weight and area then replaced it with stick on truck weights inside of the rim. You don't have to pull off the flywheel and drill remount it and try again take it off and so on. With clay you just keep adding or moving clay. You get good practice starting the engine without removing the flywheels.

Not quite -- the Mr X method balances in the horizontal plane; he was balancing in the vertical plane. To me that's a big enough difference to classify it as a different method. And again, he was not accounting for the inertia of the engine which moves the apparent heavy spot.

But that got me thinking that the best way (if using a variation of this idea) might be to balance at 45º from horizontal -- assuming you came up with an engine mount system to allow you to do it. It would seem to me that would give you empirically the best compromise between hopper and slider. It would seem to me that the Mr X method, if done until all horizontal motion is eliminated, would give you a 0% balance factor and a helluva hopper, and Andree's method would give 100% balance factor and a major slider....

[Quinnf]

[snip]  This particular flywheel is again from my Dursey built 6/1 I weighed the can once I got it correct and it weighed 2 lbs 1 1/2 OZ. [snip]

So that's 33.5 ozs.  Dave, I calculated 28.9 ozs for your Vidhata, so that's pretty close to what 38ac measured on his _real_ Lister 6/1.  Of course, we don't know what the piston and rod weights were on that engine, so can't get too excited.  Sure would be nice to chase this detail down and determine how Dursley was balancing their engines.  Even though they recommended bolting them to a concrete block, I expect they had the weights calculated so as to minimize dynamic forces as much as possible.  

Quinn

[dieselgman]

I agree, it would be interesting to find out the balancing details from original factory techniques. Anyone have a connection with David Edgington or other retired Lister employees who might shed some light?

dieselgman