Engine Balancing

Begonnen von Garnet Grylls, 27 September 2005, 05:35:04

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Garnet Grylls

Hello Everyone!

I am back at home from the UK and it is time get my R26 back together.

Before I start I want to check the balance factor of my new piston and crankshaft. I am borrowing a digital scale this weekend for the job. I have been told that 55% is the best for a single.

Does anyone know if this correct? What effect would in RPM would a change to 50 or 60% have?

Garnet G(eting smoother)

Garnet Grylls



Heiko

Hi Garnet,

there is an article about engine balancing too, but only in german  :-\\...

look here: http://www.bmw-einzylinder.de/forum/index.php?topic=276.0...

Heiko  ;)
Ariel motorcycles... upon which the sun never sets.

Garnet Grylls

Hello Heiko!

Thank you for the link. I read it once before but could not find it again :-[. When I read it long ago I knew nothing about balance factor ???, but now understand it much better ;D.

I understand that Bertl had good luck usieng a factor of 50%, or does that only aply to the 343 CCM engines? Mark Huggett said that I should use 55% which sounds like what BMW used originally.

Garnet

Rütz

Zitat...I knew nothing about balance factor...
Thank you for this admission, Garnet ;D!
I felt so very alone with my foolish answer in that topic/thread ::).

Anselm U(nbalanced)
I never dared to be radical when young.
For fear it would make me conservative when old. (Robert Frost)

Garnet Grylls

The simpilist explanation of balancing I have found comes from this site http://www.prestwich.ndirect.co.uk/technical_balancing.htm It deals with high rpm model engines but the principal it the same.

I am going to try useing their method without disassembling the crank. I will have to subtract the weight of the end of the rod from the balance factor weight and then attach the weight to the rod see what happens.
Once I think I have figured out a formula I will try and write it down :poet:.

Garnet C(onfused already)

Garnet Grylls

Some Results:

Original R26 piston... 330g
K.S. R50s piston........363g
Conrod small end......110g

I added 128g to the end of the conrod (pleulsatz?) until it balanced on a simple jig.

So I came up with this:

R26 piston-- (128 + 110)/(330 + 110)=54.09%. (Close to original BMW spec. :))

R50s piston--(128 + 110)/(363 + 110)=50.3%.

Does that make sense to anyone?

Garnet :P




† odeon8

Hi Garnet,

it does, indeed !

Using your formula my calculation is here:

R25/3 original crankshaft with 180° counterweight
Mahle 78mm Special Piston including gudgeon pin,
rings and fixture........372g
Conrod small end......114g

I added 36g to the end of the conrod (Pleuelsatz) until it balanced on a simple jig.
(This very low weight results on the excentric 32/36mm crankpin, a 44 gr. bearing and the R69/S connection rod (conrod) with a 50mm lower end bore...)

So I came up with this:

(36 + 114)/(372 + 114)=30.86%. (Shocking  :o  :o  :o)

So this  *makes* sense to me: Where can i get some tungsten (Wolfram) wing rods (Rundstäbe) ????
Alternatively i can mill some holes into the crank webs an fill them up with lead...

Thomas  ???  ::)

HUBRAUMISTDURCHNIXZUERSETZENAUSSERDURCHNOCHMEHRHUBRAUM

Knaudel

Hi,

Why should I use Wolfram?  ???

Gruß Knaudel
Keiner hat immer Recht!!

Seltener hier als Rolf und Heiko!!!

† odeon8

Hi Knaudel,

just look at the material specs:
Wolfram .......19,27 kg/dm³
Iron ...............7,87 kg/dm³
Lead..............11,3 kg/dm³

So the use of tungsten (Wolfram) allows a reduction of material volume of almost 60%.
This may be required because the space around the crank webs is limited....

Thomas

HUBRAUMISTDURCHNIXZUERSETZENAUSSERDURCHNOCHMEHRHUBRAUM

Garnet Grylls

Hey Thomas!

Don't forget to account for the force of your big fan pushing more air against the piston ;).

If you are interested, I quickly measured my 1957 R26 crank that originaly had the aluminum rod and now has a steel one. It worked out to about 25%, and vibrated badly!

After cleaning up the rolling surface on my measuring jig I came up with a balance wieght of 121g. This changes my results to:

R26 piston ....(121 + 110)/(330 + 110) = 52.5%
R50s piston...(121 + 110)/(363 + 110) = 48.8%

I am thinking taking a little bit of material off around the crankpin . I only need a few grams, do you think it is safe?

Garnet :Frage:

sjeuf12

#10
Hi Garnet,
if I had a choice then I wouldn't do that.

I believe Mark Hugget wrote a nice article on this in which he described the rebuilt of R26 aluminum conrod-cranks to steel conrod.
In the article he also mentioned the 50% balancing as a goal to achieve.
But in your case you are prepared for the two scenarios: use your R50s piston and if needed use the R26.
If you now loose weight to achieve the optimum result for the R50s piston, then you perhaps are too far off for the standard R26 piston.
But that's only my thought on this

I will try to locate that Mark Hugget story. Must be on their site but can't remember where exactly (must be old age...)

br
Ser

@Thomas
depleted uranium would also be a nice metal to use...but don't know if one can weld that...

mekgyver

#11
Hi Garnet,
Ser is right,
if you have a choice,
you better add some weights at the other side.
rho(steel)=7,85g/cm³
rho(tungsten)=19,3g/cm³
rho (difference) ~ 11,45g/cm³
you drill a hole with a volume and you win with a piece W 11,45g/cm³ .
Welding W does not work. Melting point 3400°C. Fixing is possible.
kind regards, mek  :saufen:

Ps. it is not unusual to have a crankshaft with wrong components.
The alu rod needs a crankshaft with small ~1/3 balancing wheights,
a steel rod needs a half circle balancing wheight.
Combination a steel rod and a small balancing crank will shaking terrible.
... 73er-Gang

Garnet Grylls

Hi Guys ;D

I have read that artical by Mark Huggett :). I now have the correct crank from a 59 R26 to replace the 57 aluminum rod one. I just dug it out and measured it out of interest.

The measurements listed are from the proper 59 crank. I am going to use the R50s piston and would like to get to at least 50%. I don't remeber what factor Mark stated in the artical but in an email to me he sugested 55% as a target.

Thanks
Garnet :bike:


† odeon8

Zitat von: sjeuf12 am 29 September 2005, 23:07:17
(...) Mark Hugget wrote a nice article...

Hi Ser,

do you have a link for me...my search on Google was not successful  :(

Using depleted uranium: Hard to get, even harder to work with - i think i will add some additional steel or <a href="http://www.plansee.com/hlw/500_421_DEA_HTML.htm">densimet </a>counterweights
(wedge-shaped) that are attached radially, so they could be changed while the
engine is in the bike (accessible from the oilpan)

Thomas
HUBRAUMISTDURCHNIXZUERSETZENAUSSERDURCHNOCHMEHRHUBRAUM

Karl

#14
@ Ser & Thomas:

> depleted uranium ...


Oh Jesus - what the heck you are trying to build??
A single cylinder with nuklear engine? In this case you won't have "Chrom-Eier" but "Strahlende Eier"   ;)

Hey Thomas - you could name your bike "U34/4"     ;D

Karl K(ernkraft)
Support this Board: Wer das Forum unterstützen möchte, kann das gerne per PAYPAL machen. Und hier findet Ihr meine Amazon Wunschliste.

groovebuster

Zitat von: Karl am 30 September 2005, 14:58:13
Oh Jesus - what the heck you are trying to build??
A single cylinder with nuklear engine? In this case you won't have "Chrom-Eier" but "Strahlende Eier"
His engine would have a bluish glow at night. It would fit bulls-eye to the paint-job.  ;D

Also when flooring it the exhaust gases would glow bluishly because of the ionized elements!

What a show that would be!!!  :attacke: :dance:

And glowing balls can come in handy in some situations at night... ;)  ;D

But be careful! The Americans will probably track the purchase of the Uranium and will suspect him to plan a terrorist attack with his motor-cycle!  8)

Christian W(acko)

Garnet Grylls

Hi Thomas,

I like the idea of D.U. just don't say Ahla in the same sentence :D...opps...

This is the Mark Huggett artical that I read:

http://www.bmwbike.com/index.php?=english&n=1&c=13

Type "engine balance" into the search space, and then click on 12. Re: R26 piston rod... and read Mark's reply. Sorry I couldn't make the link work :-[

Cheers
Garnet

Also http://www.cycleworks.net sells lightened gudgon pins (wristpins) that save 15 to 25 grams. That is enough to get me over 50%.

Rütz

That's the direct Link:
http://www.bmwbike.com/cgi-bin/forum.cgi?a=sm&n=2041&s=deu

Zitat...gudgon pins (wristpins) that save 15 to 25 grams..
The rest you may take off from the Piston-skirt, couldn't you?

Anselm E(asy clicking)
I never dared to be radical when young.
For fear it would make me conservative when old. (Robert Frost)

† odeon8

Thanks to Anselm for the EasyLink...

even Garnetts "how-to.." was good enough for me to get to the right location  :D

I am just reflecting on how to add 114 gramms to my crankshaft counterweights while i found the crankpin roller bearing running pretty loud.
Of course i used a dial gage (Meßuhr) to check the clearance: 0.03mm - seems to be ok.

BUT: Know a better way to check this bearing?

Look here (WMV format - 2.5MB - wait to be loaded - speakers ON).

Fix the upper part of the connection rod upside down in a vise (Schraubstock) and rotate the crankshaft manually around its crankpin - the vise is a good acoustic amplifier: If you hear something like "crrck crrck" its time to replace the roller bearing which ist a new crankpin, an updated conrod bore and a new set of rolls.... >:(
So i will send it to Uli@Frankfurt and ask for a replacement.

Best Regards - Thomas
HUBRAUMISTDURCHNIXZUERSETZENAUSSERDURCHNOCHMEHRHUBRAUM

Garnet Grylls

Thomas

You have to stop comming up with new ideas. I'm running out of money ;) Does it make any noise when you hold it by the main bearing seats and spinn the rod around?

While you where spinning your crank in the vice I was rolling mine around the kitchen watching my wife  make dinner. I wondered if the oil slinger (olschleuderblech) would have an affect on the balance. Then I wonderd if I could melt a few grams of lead inside one side of the slinger to acheive the balance I need? Do you think it will disturbe the oil flow? It is opposite side from the crank pin.

Garnet

rolf

Hey thomas,
the noise from the link:
is the bearing ok or not?
Greetings
Rolf C(rrck)

† odeon8

Hi Rolf,

the noise in the video IS from the bearing - i disassembled it and opened a new thread:
http://www.bmw-einzylinder.de/forum/index.php?topic=1956.msg18259#msg18259

So i hope that somebody can tell me what happened ...  :traurig:

Thomas
HUBRAUMISTDURCHNIXZUERSETZENAUSSERDURCHNOCHMEHRHUBRAUM

Garnet Grylls

Hello All

I added a few grams of lead into the inside of the oil slinger and polished the piston rod and crank webs around the crank pin. I am now at 51.5%.

I am afraid to take anything off the piston as I know little about where the stress points are.

Would taking weight off the flywheel be safe ??? or is it too far out of the line of force?

Granet

† odeon8

Hi "Granet"   ;),

adding some gramms of lead in the slinger reservoir is a nice idea - even i would not do it because it is not symmetrical to the crankpin. And you are right: taking off material from the piston is something for the specialists - it was done on my 78mm piston by the "piston-guru" Wahl :



They did it mainly at the inside area of the piston skirt - it works fine till now, circa 15000 km.

A lighter flywheel will accelerate the engine faster, if there is no load, will say in idle mode, no load running, not pushing you forward - so: What should it be good for? Showtime while waiting at a traffic light ?
I think the better "show" is having the idle mode been adjusted to 450 RPM; and this NEEDS a big and heavy flywheel  ;)

Thomas
HUBRAUMISTDURCHNIXZUERSETZENAUSSERDURCHNOCHMEHRHUBRAUM

rolf

Hallo thomas,
after seeing the pictures:
The noise is from a BAD bearing  ;D

Garnet Grylls

Yes Thomas

The "Granet" is mostly in my head.

Could you lighten your crankpin by boring out the centre more? That would be a big help for balance.

I took the few grams of lead out of the oil slinger :-[. It did not lay smooth in the bottom and I was concerned that it would make the oil foam.

I bored some holes in the crank web and filled them with lead and am much happier  ;D. It required 6 holes. Tungston would have been much better.

Garnet R(ocky)

Garnet Grylls

Hello everyone.

Here are my final results:

New piston (complete)..........363 g
Con-rod end .........................111 g
Counter balance ...................141 g

So:  (141 + 111)/(363 + 111) = 252/474 = 53.16% 8)

If I get a 15 g lighter gudgeon pin
then: (141 + 111/(348 + 111) = 252/459 = 54.9%  :dance:

So now I am moveing on to reassmbily

Garnet

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