Previous Thread
Next Thread
Print Thread
Rate Thread
Force needed to raise a bent #29841 11/26/12 06:29 PM
Joined: Feb 2006
Posts: 332
H
Housewright Offline OP
Member
OP Offline
Member
H
Joined: Feb 2006
Posts: 332
We had a very smooth hand raising yesterday. This was the first hand raising I have planned and the walls went up easier than I expected (leaving some people with the bad feeling of being un-needed). We had 25 people on pikes and ten people just lifting with their hands and then the people on the ropes, stays and safety devices I had.

In planning the number of people needed to lift a wall by hand I took the weight of the 20' plate and half of the 10' posts as the weight to lift when the wall was laying down. My question is how do I figure out what the force needed to push the wall at various angles as the wall is going up? For example when the wall is half way up (45 degrees) what force is needed to hold it from coming back down? Is it simply one-half of the starting weight?

Know what I mean?
Jim


The closer you look the more you see.
"Heavy timber framing is not a lost art" Fred Hodgson, 1909
Re: Force needed to raise a bent [Re: Housewright] #29848 11/27/12 11:01 PM
Joined: Mar 2002
Posts: 1,676
J
Jim Rogers Online Confused
Member
Online Confused
Member
J
Joined: Mar 2002
Posts: 1,676
When ever we did a hand raising at Fox Maple school, Steve figured the weight of the frame pieces. All of them, in the bent, post, braces, and tie for example.
Now we're not lifting the entire bent off the ground, only pivoting it up. So he figured that 2/3's of the weight was going to be at the post foot to the ground.
So a 1500 lbs bent would only need 500 lbs of lift.

He figured that the average person could easily lift 50 lbs. So 500 divided by 50 = 10 people to lift the bent.

When we do a hand raising we have a safety rope going back to hold it bent from going over too far, as well as one to pull to help put it up. I think last time we had about three people on each line. I'd have to check the pictures to make sure, but that's what I remember.

Glad it went well for you.

Jim Rogers


Whatever you do, have fun doing it!
Re: Force needed to raise a bent [Re: Jim Rogers] #29850 11/28/12 12:27 AM
Joined: Feb 2012
Posts: 54
R
Roger W Nair Offline
Member
Offline
Member
R
Joined: Feb 2012
Posts: 54
The Fox Maple calc of lift should not be considered as general advice. The weight and configuration of the timber needs to go into a center of gravity calc then the lift needs to be evaluated as a lever. The load varies as the frame tilts upwards and at the angle as force is applied. The ideal angle of pikes should be parallel to the tangent of the arc of rotation, this is important for the initial application of pikes, force increases, in both directions, as pikes deviate from parallel.

Last edited by Roger W Nair; 11/28/12 12:30 AM.

Moderated by  Jim Rogers, mdfinc 

Newest Members
GBL, Jeff_Mayhew, Newman, BrianDumais, Doug_Evans
5076 Registered Users
Powered by UBB.threads™ PHP Forum Software 7.7.3
(Release build 20190728)
PHP: 5.4.45 Page Time: 0.023s Queries: 15 (0.006s) Memory: 3.1220 MB (Peak: 3.5828 MB) Data Comp: Off Server Time: 2022-08-15 16:54:28 UTC
Valid HTML 5 and Valid CSS