E: Engine Crankshaft Balance Method

Brian Thompson

Well Known and Active Forum User
Non-VOC Member
I have the Twin running nicely in the original frame and was about to put it in a Mcintosh Egli frame. It has one of Terry's 40 mm big end and 30 mm main shaft cranks in it with 600 cc top end kits on it. Its nice and smooth in the Vin frame. I"m hoping it doesn't vibrate to much when it moves into its new home. ( Won"t happen for a while now) I didn't ask Terry what this cranks balance factor is. I"m sure if there was an issue he would have mentioned it. It has 350 gram pistons. The newer pistons I have are 300 grams. Does anyone else have this combination in an Egli style frame?
Cheers
Brian
 

Bill Thomas

Well Known and Active Forum User
VOC Member
Can you go blow by blow with us as you do it Greg, I am still not sure of the maths.
There is a bloke on youtube that is different, And most people think he is right.
 

greg brillus

Well Known and Active Forum User
VOC Member
Terry's cranks are pretty much set at 60%........... The balance of a crank in a stock frame should be near identical to the Egli frame on account of how it's mountings are the same......... When the engine is in a partial or full loop frame, that is different....... well going off the run of series "A" twins I have done recently.......and building 2 Norvin's, a single (my racer) and a 1200 Twin as we speak.
 

Vincent Brake

Well Known and Active Forum User
VOC Member
I noticed
At 48% a more up n down vibration.
And over 52% a more fore and aft one.

Guess it also has to to with the secondary vibration.

Now i want a straight six
 

timetraveller

Well Known and Active Forum User
VOC Member
I think that Vic is a hero building his own dynamic balancing rig. One suggestion which might already be incorporated is to mark the rim of the flywheels with numbers every centimetre or so. That way the strobe will show a number and the position. Good luck with it Vic.
 

oexing

Well Known and Active Forum User
VOC Member
Norman,
I don´t have a strobe on the rig but get positions from the electronics for each side, for adding weights or drilling for reduction. Only questionable setup is my stickers or felt pen marks for getting a rough idea about circular positions. I can use the woodruff key slot on the SR cranks for zero position -and the rest is a bit of guesswork and eyesight. Certainly one could add a degree disc on the mainshaft end but then I do this only once in a few months for a friend with his hobby workshop.
In case somebody were interested in that kind of equipment - I got the professional tester with a lot of luck from Ebay € 500.- or so - I first tried a USB hobby kit from Australia but somehow this did not work as promised, maybe broken. So I could get help from an oscillograph app on the laptop hooked to the g-sensors and with many test runs I achieved great smoothness.
Here is a link and youtube clips about this USB Dynex Hobby kit for € 150.- or so which got about the same logic as my prof tester. But you have to do a lot of configuration on your computer to see useful results. So when I found my tester on Ebay I just had to have it.

Vic

Dynex Hobby kit:
P1050316.JPG


HRD crank with Dynex:
P1050258.JPG


laptop app Dynex:
P1050263.JPG


youtube Dynex

Dynex Hobby home
 
Last edited:

Little Honda

Well Known and Active Forum User
Non-VOC Member
Norman,
I don´t have a strobe on the rig but get positions from the electronics for each side, for adding weights or drilling for reduction. Only questionable setup is my stickers or felt pen marks for getting a rough idea about circular positions. I can use the woodruff key slot on the SR cranks for zero position -and the rest is a bit of guesswork and eyesight. Certainly one could add a degree disc on the mainshaft end but then I do this only once in a few months for a friend with his hobby workshop.
In case somebody were interested in that kind of equipment - I got the professional tester with a lot of luck from Ebay € 500.- or so - I first tried a USB hobby kit from Australia but somehow this did not work as promised, maybe broken. So I could get help from an oscillograph app on the laptop hooked to the g-sensors and with many test runs I achieved great smoothness.
Here is a link and youtube clips about this USB Dynex Hobby kit for € 150.- or so which got about the same logic as my prof tester. But you have to do a lot of configuration on your computer to see useful results. So when I found my tester on Ebay I just had to have it.

Vic

Dynex Hobby kit:
View attachment 32127

HRD crank with Dynex:
View attachment 32128

laptop app Dynex:
View attachment 32129

youtube Dynex

Dynex Hobby home
Vic,
do I see correctly: The device operates with a swinging arm of sheeted metal left and right, carrying two
rolls to take the crank each side, taking the wired gravity sensors inside the sheeted metal plates, being
wired to the electronic unit on the left base plate which measures the varying loads in grams, when the
crank starts rotating, driven by the belt, tensioned by a tensioning roll?
An admittedly beautiful tool to work with. Congratulation to your buy at ebay!
 

oexing

Well Known and Active Forum User
VOC Member
Salü,
yes, the two ball bearings at each side sit on their mini linear guide with rubber stops to limit lateral strokes. I did not want rubber elements there as a crank can have some more kilograms so better have a sturdy rig. The last photo above shows the Dynex kit that I have binned for the professional test equipment. The crank supports have g-sensors no. 1 and no. 2 at the ends which are hooked up to the electronics and send acceleration readings into the set. A proximity switch at the right mainshaft picks up on the woodruff key for taking revolutions and angular position - roughly. This night I got the feeling that the proximity switch is not quite OK when finishing the second SR crank. Have to check my stock . . . .
Below is the present setup with a SR crank - as shown in the youtube clip.

Vic

previous Dynex kit with HRD crank
P1050246.JPG


professional sensors and SR crank
P1070224.JPG
 

Little Honda

Well Known and Active Forum User
Non-VOC Member
Vic,
do I see correctly: The device operates with a swinging arm of sheeted metal left and right, carrying two
rolls to take the crank each side, taking the wired gravity sensors inside the sheeted metal plates, being
wired to the electronic unit on the left base plate which measures the varying loads in grams, when the
crank starts rotating, driven by the belt, tensioned by a tensioning roll?
An admittedly beautiful tool to work with. Congratulation to your buy at ebay!
Salü,
yes, the two ball bearings at each side sit on their mini linear guide with rubber stops to limit lateral strokes. I did not want rubber elements there as a crank can have some more kilograms so better have a sturdy rig. The last photo above shows the Dynex kit that I have binned for the professional test equipment. The crank supports have g-sensors no. 1 and no. 2 at the ends which are hooked up to the electronics and send acceleration readings into the set. A proximity switch at the right mainshaft picks up on the woodruff key for taking revolutions and angular position - roughly. This night I got the feeling that the proximity switch is not quite OK when finishing the second SR crank. Have to check my stock . . . .
Below is the present setup with a SR crank - as shown in the youtube clip.

Vic

previous Dynex kit with HRD crank
View attachment 32130

professional sensors and SR crank
View attachment 32131
why not fitting ignition pick-ups at any side of the crank, ie. Sachse Ignition, which allows precision to less
than 1 deg.? What about primary drive components re balancing? I bet, that´s a lot more than 1 gr.
 
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