Slant Six Forum
https://slantsix.org/forum/

How to make a crank lighter
https://slantsix.org/forum/viewtopic.php?t=36669		 Page 1 of 1
Author:  plymouth6 [ Sun Aug 09, 2009 10:23 pm ]
Post subject:  How to make a crank lighter
As I have posted before I am building a Drag motor and want to know how to take weight off the crank? I will be using a forged crank and using this motor at the track only. I read the Hot Rod article and saw that Doug Dutra has taken 21 pounds off of some of his cranks. So where do I start and what is the best tool to use for this? Thanks.
Author:  Doc [ Mon Aug 10, 2009 9:52 am ]
Post subject: 
I have lightened a few SL6 forged cranks over the years and doing that job is a bunch of work for little gain. A hand-held band saw, die grinder, big drill press and a large grinder are the tools for the task.

My current thinking is to start with the lightest SL6 crank to begian with, the 82-86 cast crank. These start at 60 lbs and can be taken to 58 pretty easily.

If you really want to lighten the forged crank, start by sawing-off all the "balancing lugs", these are the big lumps of extra steel that the factory uses as drilling points, to balance the cranks.

Next step is to "knife edge" all leading edges. (direction of rotation)

The last step is to check balance and work on the large center weight to get the balance "in the ball-park" , then work on the ends to get the final balance.
DD

Image
Author:  NCDemon1971 [ Mon Aug 10, 2009 12:13 pm ]
Post subject: 
Quote:
I have lightened a few SL6 forged cranks over the years and doing that job is a bunch of work for little gain. A hand-held band saw, die grinder, big drill press and a large grinder are the tools for the task.

My current thinking is to start with the lightest SL6 crank to begian with, the 82-86 cast crank. These start at 60 lbs and can be taken to 58 pretty easily.

If you really want to lighten the forged crank, start by sawing-off all the "balancing lugs", these are the big lumps of extra steel that the factory uses as drilling points, to balance the cranks.

Next step is to "knife edge" all leading edges. (direction of rotation)

The last step is to check balance and work on the large center weight to get the balance "in the ball-park" , then work on the ends to get the final balance.
DD

Image
I dont guess you could really mess one up could you? If you were gonna rebalance the assembly anyways??
Author:  slantfin [ Mon Aug 10, 2009 1:47 pm ]
Post subject: 
Quote:
I dont guess you could really mess one up could you?

I'm pretty sure I could. It's something of a specialty of mine. :?
Author:  Doc [ Mon Aug 10, 2009 2:06 pm ]
Post subject: 
The most important thing is to start with a good crank to begain with. :idea:

I always start with a nice standard journal size, big rear hub, not welded-on, not bent, not cracked, no stripped-out holes type core.

The next tip is to tape-over all the journals and the front snout / rear flange... use many layers of duct tape.

There is always a risk that if you get the crank too light for the amount of HP the engine makes, the lightened crank will twist, crack or break in use.
DD
Author:  plymouth6 [ Mon Aug 10, 2009 6:57 pm ]
Post subject: 
Thank you very much for the info Doc. Have you done any testing to see what difference it makes in the HP area?
Author:  darrt wells [ Tue Aug 11, 2009 5:03 pm ]
Post subject: 
Doc, with that knife edged crank, was there much gain in RPM?
Author:  Wizard [ Tue Aug 11, 2009 5:07 pm ]
Post subject: 
It is not the RPM, nor horse power. The idea is how quickly the crank accelerates from low rpm.

Cheers, Wizard
Author:  plymouth6 [ Wed Aug 12, 2009 3:06 pm ]
Post subject: 
I would think with a lighter rotating assembly you would gain a little HP but I have been wrong before.
Page 1 of 1 All times are UTC-08:00
Powered by phpBB® Forum Software © phpBB Limited
https://www.phpbb.com/