ESE's works engine tuner

[Grumph]

Thanks for the heads up. I thought weighing the reciprocating mass and then hanging a percentage of its mass off the end of the conrod was the way to go. I will have to re visit how I am doing this.

Method is fine. Arithmetic needs tweaking.

[TZ350]

Where is your con rod in that second picture? The weight of its small end should be part of the 186 g.
186 g plus the small end weight will give a notably higher balance factor (which in practice may not be a bad thing).

Method is fine. Arithmetic needs tweaking.

Ok. Looks like I incorrectly calculated the mass to be balanced.

I had included the little end of the con rod in the reciprocating mass calculation Step-1, but by not including it in Step-2 I had inadvertently included it's effect twice when calculating the mass required to be balanced in Step-2.

Looks like I should have made my calculation:-

Step-1 Reciprocating Mass X B/F% = "B/F Mass required"

Step-2 Weigh con rod little end plus hook and washers until you have the"B/F Mass required" to hang on the end of the rod.

Step-3 add/subtract mass from/to the cranks counter weight side to achieve static balance.

I think they make the same mistake in this description of how to balance a single cylinder crankshaft.

2 Stroke Stuffings take on finding the existing balance factor. https://youtu.be/0hoE_MuFpPI

[Grumph]

Moments like this I always go back to good old Phil Irving. Pretty well every book he ever wrote - except his autobiography - had the method and formulas for crank balancing included. Pre internet references for a process which predates the internet.


Probably showing my age there.....

[husaberg]

Moments like this I always go back to good old Phil Irving. Pretty well every book he ever wrote - except his autobiography - had the method and formulas for crank balancing included. Pre internet references for a process which predates the internet.


Probably showing my age there.....

.

There has been a bit of talk about Crank Shaft Balance Factors on the Two Stroke Tuners thread, resulting in more heat than light. As there is a bit of a rowdy crowd over there I am going to make my posts here.

I intend to keep it simple, so for what its worth, this is our interpritation of Phill Irvings work.

Phill Irving talks about CrankShaft Balancing and Balance Factors on pages 107 to 110 of the book which can be found on page 61 of the PDF.

http://www.scribd.com/doc/15392252/T...rcycle-Engines

Anyone can open a free account with Scribed where they can download "Tuning for Speed" by Phill Irving.

"xwhatsit" is the guy who uploaded Tuning for Speed to Scribd in the first place, thanks xwhatsit.


I will use a 2-Stroke single cylinder TF100 crank to demonstrate my explanations and I need to break it down into sections as I can't cover it all in one or two posts. Thomas gave me a hand, taking the photos and gave me a few tips along the way.


My plan is to:-

(1) Post photos of all the cranks I have lying around and quickly describe the features I can see on them.

(2) Describe how to find the reciprocating weight.

(3) What the "Balance Factor" really is.

(4) I will answer this question, Which is heavier, (A) the reciprocating weight of the rod piston assembly or (B) the counter weight of the crankshaft.

(5) Why there is a "Balance Factor" and what changing it does.

(6) What to do with your "Balance Factor"

(7) A simple but very effective jig for staticaly balancing a crank, that you can make yourself in 10min's. (Thanks Thomas)

(8) What a rocking couple is, and how the term is used in crank shaft balancing.

(9) Just for Skunk, Some of the problems associated with balancing a V2 90 degree twin with one horizontal cylinder.


This is going to be a very simple "KISS" look at single cylinder crankshaft balancing, based on Phill Irvings book. If anyone thinks I've missed something or wants a more in-depth treatment they are welcome to explore the internet for what they can find. Or dust of data from their own experiments and post it themselves. Then we can all enjoy reading their interpretation of what they have learnt.

.

plus 10.....

For those too lazy

[F5 Dave]

I'm definitely too lazy to exercise blandishment in the right quarters.

[Splatter]

hello muhr, i've seen your 50cc project while reading some pages back.. have you finally tried it? that looked nasty.



amazing quality. have you also experienced an improvement restricting the internal cross section instead of maintaining the carb exit cross section?
Have you tested different lenghts for the horizontal splitter? i see that this goes all the way from the base to the top of the cusp.
I even saw someone on the dutch forum (deraceheldenvanweleer.nl) hypothesizing a manifold with a continuation of the splitter, but i can't find any feedback on that.

The splitter is full length for several reasons. The material used does not work well using supports so it's easier and better quality to print the splitter off the print bed. The area of the splitter is considered when figuring out the total flow area. The cross section is smaller than the carb size. The other reason for the full length cage splitter is that it connects to the splitter in the intake. The intake splitter is curved with the angle of the intake to try and maintain equal flow to the top and bottom of the cage.

[Splatter]

Your 1/2 moon fillers look really nice , but I now make them with no step up to the petal seal surface on the sides.
This does not apply to the end of the splitter at the reed tips , a right angle step here , on the flow bench lifts the petals higher and faster - resulting in more power on the dyno as well.
Completely counter intuitive to having a triangle divider under the petal tips - but hey its a 2T so reality doesn't match anyone's pre conceived ideas.

Also the splitter is shortened , it starts where the venturi ends , further in from the block entry face.
As we also bias the flow upward toward the piston by having asymmetric reed backups , im about to try moving the front edge of the airfoil splitter downward , too force more flow into the top pair of reed block ports.

Edit - the guys who make the UFO for Mikuni round slides also make a short splitter that divides the carb exit in 1/2 at the engine side of the slide.
This gives way better response at low throttle openings - so the idea could be extended so the reed splitter is continuous right up to the throttle slide - maybe ?

That is an older cage pic. The current cage has no step on the sides. The splitter extends into the intake where it curves with the angle of the intake, but only to the carb boot. Maybe I should try extending it to the slide. This cage has no lip at reed exit and I'm trying to use the case pressure changes to lift and hold open the reeds. Data aq and lap times show it works, but I haven't dyno'd it. I have limited dyno access for the bigger engines. I do have access to a smaller engine dyno and am making one of these to test on a TM R2 just for proof of concept. I'm using soft reeds (30.5) with no stiffeners and they are working well with decent longevity, but we only rev these to 9500.

[Frits Overmars]

Ok. Looks like I incorrectly calculated the mass to be balanced..... I think they make the same mistake in this description of how to balance a single cylinder crankshaft.

Yes they do. First they make it more complicated than it needs to be by working with 100% minus the balance factor instead of simply working with the balance factor itself.
And then they forget that 100% of the small end weight (I should really say mass instead of weight) is already there, hanging from the big end pin.

2 Stroke Stuffings take on finding the existing balance factor. https://youtu.be/0hoE_MuFpPI

I like this video. From 3:30 Aleks Degnes (mr. 2Stroke Stuffing) says: "Place the weight you added to the con rod on your scale, remember to include the wire hook,
add the con rod weight to hung weight....."
So Aleks is in the clear. Just as well, because he's coming over next week to sniff some two-stroke fumes here. Now I won't need to lecture him

[wobbly]

Splatter , yea buddy that cage looks dead cool , now try the step under the reed tips , it worked well for me in the TM R1 and now the R2 as well.
The company I used originally to print stuffers used a process of putting the part in a box with I think acetone fumes , this fused the surface into a smooth shiny finish.

[monkeyfumi]

The company I used originally to print stuffers used a process of putting the part in a box with I think acetone fumes , this fused the surface into a smooth shiny finish.

The process is Vapour polishing. Be careful if you attempt it though, heating acetone can be dangerous

https://www.youtube.com/watch?v=PegrypbCwag

[philou]

for crankshaft balancing. an old idea is circulating. on the primary side only insert 2 weights at 90 and 270 degrees from the crank pin to change its vibration frequency in addition to bringing additional inertia

[41juergen]

just a question maybe mainly to Wob and Frits: when talking about the crankcase compression ratio you use Neels definition (meaning excluded the transfer duct volumes), correct?
cheers
Juergen

[philou]

in my opinion the software adds them.

they are part of the volume since they communicate directly with

[Frits Overmars]

when talking about the crankcase compression ratio you use Neels definition (meaning excluded the transfer duct volumes), correct?

My definition for crankcase compression ratio is

(volume below the piston dome at TDC) / (volume below the piston dome at TDC - cylinder capacity)

and for me, volume below the piston dome at TDC includes the transfer duct volumes.

Of course this is just a geometric approach. One can argue that crankcase compression can only begin when the inlet is closed, and it ends when the transfers start opening.
So the crankcase compression ratio is just a number. The crankcase volume, in combination with the transfer ducts and above all the exhaust system, determines the engine's pressure fluctuations and resonance frequency.

[Splatter]

Splatter , yea buddy that cage looks dead cool , now try the step under the reed tips , it worked well for me in the TM R1 and now the R2 as well.
The company I used originally to print stuffers used a process of putting the part in a box with I think acetone fumes , this fused the surface into a smooth shiny finish.

Thanks, I will try a step. I haven't found a chemical solution to smoothing this material. The fiberglass in it might be a problem anyway. It can be sanded, but I'm not that dedicated.