This is a short video I made showing china girl crankshaft runout.
http://www.youtube.com/watch?v=CZv_sVNC_q0
http://www.youtube.com/watch?v=CZv_sVNC_q0
China Girl Motor Crankshaft Runout Video
- Thread starter biknut
- Start date
Re: China Girl Crankshaft Runout Video
So how do you fix that runout?
Sand it, grind it, bend it?
JB weld?
Do tell!
So how do you fix that runout?
Sand it, grind it, bend it?
JB weld?
Do tell!
Re: China Girl Crankshaft Runout Video
At first I tried using only one dial indicator, but that's hard to do. You pretty much need to be able to look at both shafts at the same time.
Basically you locate the high spot on the shaft, and then you figure out where you need to whack the flywheel with a hammer to make it a lower spot. It's not that hard from trial and error to figure out where to whack it. The hard part is getting a way to accurately measure the runout.
At first I tried using only one dial indicator, but that's hard to do. You pretty much need to be able to look at both shafts at the same time.
Re: China Girl Crankshaft Runout Video
You force it back into alignment , with a press or a hammer I've seen both used . Hope that helps . Dan
Re: China Girl Crankshaft Runout Video
It's a lot easier to balance the crank than it is to true it. It's not going to do much good though if your crank has too much runout, so true first, then balance.
Re: China Girl Crankshaft Runout Video
I doubt it. This is my first attempt, and it's proving to be very time consuming. I hope I can think of a way to get better at it.
Re: China Girl Crankshaft Runout Video
I wish Fouresay was still into motorized bicycling.
He said he had balanced cranks that run 3500~11000 rpm smooth as silk for $100 each.
I wish Fouresay was still into motorized bicycling.
He said he had balanced cranks that run 3500~11000 rpm smooth as silk for $100 each.
Re: China Girl Crankshaft Runout Video
For the 44-47mm piston, drill 2 holes one on each side of the connection rod hole. Hole size should be 11mm this will remove around 49g of material. This will balance the crank well. For 40-44mm piston , drill 8mm holes to remove 39g. These are close approximations and will help balance non balanced cranks. Enjoy the ride.
For the 44-47mm piston, drill 2 holes one on each side of the connection rod hole. Hole size should be 11mm this will remove around 49g of material. This will balance the crank well. For 40-44mm piston , drill 8mm holes to remove 39g. These are close approximations and will help balance non balanced cranks. Enjoy the ride.
Re: China Girl Crankshaft Runout Video
To measure run-out, you need to have the mains centerless (rolling on the journal on a pair of bearings), or it's worthless. The dial indicators moved in a pattern that looked like a crank suspended on off-set centers.
Nothing done to a crank should be indicated by features on the ends of the shaft.
I balanced a few hundred cranks for various engines when I worked in the racing engine field, never did a single cylinder crank though. The math for calculating your bob weights to find ideal counter balance moment should be pretty easy though, just get the dynamic weight of your piston rod assembly (you weigh both sides with the piston on the rod, hanging from the wrist pin to be horizontal when the big end is on, and visa versa).
You should be able to find guides for measuring and setting up bob weights on single cylinder engines.
To measure run-out, you need to have the mains centerless (rolling on the journal on a pair of bearings), or it's worthless. The dial indicators moved in a pattern that looked like a crank suspended on off-set centers.
Nothing done to a crank should be indicated by features on the ends of the shaft.
I balanced a few hundred cranks for various engines when I worked in the racing engine field, never did a single cylinder crank though. The math for calculating your bob weights to find ideal counter balance moment should be pretty easy though, just get the dynamic weight of your piston rod assembly (you weigh both sides with the piston on the rod, hanging from the wrist pin to be horizontal when the big end is on, and visa versa).
You should be able to find guides for measuring and setting up bob weights on single cylinder engines.
Re: China Girl Crankshaft Runout Video
liveforphysics, can you sell me a balanced crank for the chinese motors?
liveforphysics, can you sell me a balanced crank for the chinese motors?
Re: China Girl Crankshaft Runout Video
As far as these cranks go though, I've never even touched one, and would like to avoid it happening if possible. it's been many years since I was slaving over and old warner balancer with a pile of SBC/SBF/BBC cranks on a rack waiting for my attention. I still have a few gas powered motorcycles and racecars, but electric is all I focus my passion towards now. Just wanted to provide a little guidance to a thread that looked to be needing a bit.
I don't sell stuff, I only give cool parts away. I'm not really into the money thing.
As far as these cranks go though, I've never even touched one, and would like to avoid it happening if possible. it's been many years since I was slaving over and old warner balancer with a pile of SBC/SBF/BBC cranks on a rack waiting for my attention. I still have a few gas powered motorcycles and racecars, but electric is all I focus my passion towards now. Just wanted to provide a little guidance to a thread that looked to be needing a bit.
Re: China Girl Crankshaft Runout Video
Biknut,
Look forward to your dedication on truing HT crankshafts.
In my research of the subject, I've found that most posts recommended using machinist V-Blocks, rather than a lathe. The V-blocks are more accurate than a lathe which requires tuning and adjustments. I don't think you'll get a wood lathe near the accuracy of V-Blocks.
Here's a post to check if your centers are aligned. This might indicate how accurate your measurements are. About 2/3 down the page - shows using a 0.005 - 0.015 feeler gauge leaf to measure alignment:
http://www.mini-lathe.com/Mini_lathe/Tuning/tuning.htm
I am not a machinists or mechanic - Just my 2 cents.
Keep up the pursuit and I look forward to your continued journey.
Chris
AKA: BigBlue
Biknut,
Look forward to your dedication on truing HT crankshafts.
In my research of the subject, I've found that most posts recommended using machinist V-Blocks, rather than a lathe. The V-blocks are more accurate than a lathe which requires tuning and adjustments. I don't think you'll get a wood lathe near the accuracy of V-Blocks.
Here's a post to check if your centers are aligned. This might indicate how accurate your measurements are. About 2/3 down the page - shows using a 0.005 - 0.015 feeler gauge leaf to measure alignment:
http://www.mini-lathe.com/Mini_lathe/Tuning/tuning.htm
I am not a machinists or mechanic - Just my 2 cents.
Keep up the pursuit and I look forward to your continued journey.
Chris
AKA: BigBlue
Re: China Girl Crankshaft Runout Video
V-blocks are MUCH better because they are centerless (which is the only way you can check a crank's runout).
Unlubed, they tend to chaffe though, and lubed they tend to float a couple tenths as they turn, and then settle when they sit, so your runout reading has a bit of artifact in it.
Rollers are really the only way to do it right. You can make a set of roller blocks for about $40 in materials.
V-blocks are MUCH better because they are centerless (which is the only way you can check a crank's runout).
Unlubed, they tend to chaffe though, and lubed they tend to float a couple tenths as they turn, and then settle when they sit, so your runout reading has a bit of artifact in it.
Rollers are really the only way to do it right. You can make a set of roller blocks for about $40 in materials.
Re: China Girl Crankshaft Runout Video
A lathe, V Blocks, and a Roller are 3 different ways to do it, right?
Wow what a great article about tuning up a lathe. Kind of blows my little mind really. That's how little I know. Kind of explains some inconsistances I've been seeing. I didn't understand what was going on.
A lathe, V Blocks, and a Roller are 3 different ways to do it, right?
Re: China Girl Crankshaft Runout Video
Live,
Roller Block?
Is this what you mean?
http://motorbicycling.com/attachment.php?attachmentid=49183&stc=1&d=1340258759
Chris
AKA: BigBlue
Live,
Roller Block?
Is this what you mean?
http://motorbicycling.com/attachment.php?attachmentid=49183&stc=1&d=1340258759
Chris
AKA: BigBlue
Attachments
Re: China Girl Crankshaft Runout Video
I like those roller blocks. I see what you're talking about. They would probably come in handy for balancing too.
Re: China Girl Crankshaft Runout Video
For these little crank, you might need to make your own with narrower bearings and thinner edge plates if that block is too wide to clear the journal.
Yep. Thats exactly what I'm taking about, and it's THE tool for getting a decent run-out measurement.
For these little crank, you might need to make your own with narrower bearings and thinner edge plates if that block is too wide to clear the journal.