- -
Engine balancing
(
http://www.clubcobra.com/forums/small-block-talk/113550-engine-balancing.html)
| xb-60 |
12-13-2011 03:11 AM |
Quote:
Originally Posted by blykins
(Post 1165173)
|
Just got to it Brent. Like they say, a picture's worth a thousand words. So it seems that a non-race engine, up to 6500rpm max, external balance is sufficient. So how many - what percentage - of these engines would you internally balance? And what's a typical added cost to a motor for blueprinting/balancing?
Cheers,
Glen |
| xb-60 |
12-13-2011 03:13 AM |
Quote:
Originally Posted by Jerry Clayton
(Post 1165188)
http://www.scatcrankshafts.com/scatt...k_the_Nose.pdf
After you have watched that video, check out number 5 of this page---in the video look at all the holes he drilled into the counter weights to try to balance the assy with external weighed flywheel and dampner--In Scat's tech section in very plain language talk about how much to drill and this guy evidently didn't read it--
|
So, what - would that crank go out as a balanced crank, or would it be a scrapper, Jerry?
Cheers,
Glen |
| xb-60 |
12-13-2011 03:18 AM |
Quote:
Originally Posted by blykins
(Post 1165234)
Haha....the wolves are out tonight....
Remember guys, this is a very fundamental thread on balancing. We're not teaching him to be a machinist.
|
Yep, thanks. Keep it relatively fundamental. I like to understand the concepts, but the wolves make for interesting reading as well, and the 'oversight committee' might just make it better/safer for us sheep as well... |
| xb-60 |
12-13-2011 03:19 AM |
Quote:
Originally Posted by blykins
(Post 1165262)
You win some, you lose some....
This thread should be looking at the forest though....not the trees... ;)
|
I get your point. The forest looks OK |
| xb-60 |
12-13-2011 03:27 AM |
Quote:
Originally Posted by CHANMADD
(Post 1165289)
Most engines have an imbalance at 1400_2000 rpm. This is harmonic imbalance.The harmonic balancer helps to absorb that frequency. Most harmonic balancer have arubber ring sandwiched berween two parts. This type of balancer should be balanced with the crank. A fluid filled type balancer cannot be spun balanced because the fluid moves around. The 28 oz thing is like balancing a wheel and on one side there is a big hole drilled , so that before you stick it on the machine you know that you drilled out 28oz, so that exactly opposite at the same circumference you attach a 28oz weight to get the balance close before spin balancing on the machine.
A single cylinder motor would have all the components meticulously polished ,shaped etc.
A blueprint is making sure that all the components match exactly the designers specs.
A multicylinder blueprint is making sure that all the cylinders and all related components are exactly the same, down to 0.002 of a gram. When they are all same the harmonics will be minimized and then spin balancing will require less addition or removal of metal. This is what makes motors live.
Look at the pulley on a good timiing chain set...it should have some balancing drill marks.
So....yes balance everything if you can..it can only make things smoother
John
|
John - if you drill a hole on one side and then add material exactly opposite, would that not make the imbalance worse?
Cheers,
Glen |
| blykins |
12-13-2011 04:13 AM |
Quote:
Originally Posted by xb-60
(Post 1165383)
So how many - what percentage - of these engines would you internally balance? And what's a typical added cost to a motor for blueprinting/balancing?
Cheers,
Glen
|
If I'm building the engine from the ground up, it will usually get internally balanced.
Blueprinting has nothing to do with balancing, it's part of the mock-up and assembly process.
A balance job will start at around $200 and can easily go past $400-500 if a lot of heavy metal needs to be added. The last Scat forged 351C rotating assembly that I did required 6 pieces of heavy metal, even with an I-beam rod and a Diamond piston. That added a huge amount to the balancing bill... |
| xb-60 |
12-13-2011 04:47 AM |
Quote:
Originally Posted by blykins
(Post 1165406)
If I'm building the engine from the ground up, it will usually get internally balanced.
Blueprinting has nothing to do with balancing, it's part of the mock-up and assembly process.
A balance job will start at around $200 and can easily go past $400-500 if a lot of heavy metal needs to be added. The last Scat forged 351C rotating assembly that I did required 6 pieces of heavy metal, even with an I-beam rod and a Diamond piston. That added a huge amount to the balancing bill...
|
That sort of cost sounds reasonable to me.
Doesn't blueprinting involve selecting components, or adjusting components (as was seen in that You-Tube video, where the conrods were being ground) so that they are the same weight?
Cheers,
Glen |
| blykins |
12-13-2011 04:57 AM |
To me, that's part of the balancing process.
The pistons/rings/bearings/rods, etc. should be selected before hand as part of the engine qualification process.
Blueprinting to some just means checking the parts out. It's really a lot more involved than that...coming up with a plan, figuring out what clearances/dimensions you need, then making everything fit that plan.
|
| Jerry Clayton |
12-13-2011 08:58 AM |
If a customer showed up here with those parts, I would send him on his way--that crank is scrap and the balance guy would be looking for work doing something else---
|
| CHANMADD |
12-13-2011 10:39 AM |
K
Quote:
Originally Posted by xb-60
(Post 1165393)
John - if you drill a hole on one side and then add material exactly opposite, would that not make the imbalance worse?
Cheers,
Glen
|
yes...:I was typing on the move......little brain phart right there....but I trust you understood what I meant. |
| CHANMADD |
12-13-2011 10:43 AM |
The crank in the video became scrap because too much material was removed. If parts selection and balancing had been done it would not have required such extreme drilling.
|
| xb-60 |
12-13-2011 02:06 PM |
Quote:
Originally Posted by CHANMADD
(Post 1165445)
K
yes...:I was typing on the move......little brain phart right there....but I trust you understood what I meant.
|
phart understood |
| All times are GMT -7. The time now is 09:31 AM. |
|
Powered by vBulletin® Version 3.8.0
Copyright ©2000 - 2026, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.6.0
The representations expressed are the representations and opinions of the clubcobra.com forum members and do not necessarily reflect the opinions and viewpoints of the site owners, moderators, Shelby American, any other replica manufacturer, Ford Motor Company. This website has been planned and developed by clubcobra.com and its forum members and should not be construed as being endorsed by Ford Motor Company, or Shelby American or any other manufacturer unless expressly noted by that entity. "Cobra" and the Cobra logo are registered trademarks for Ford Motor Co., Inc. clubcobra.com forum members agree not to post any copyrighted material unless the copyrighted material is owned by you. Although we do not and cannot review the messages posted and are not responsible for the content of any of these messages, we reserve the right to delete any message for any reason whatsoever. You remain solely responsible for the content of your messages, and you agree to indemnify and hold us harmless with respect to any claim based upon transmission of your message(s). Thank you for visiting clubcobra.com. For full policy documentation refer to the following link:
