finding the center of gravity...(machine dolly-design related)
 

need to build a (retractable wheels) dolly for my big saw. the huge
motor, and other thick cast iron parts, stick out to one side, and
rearward. I'd prefer to space the wheels 'relative to' the center of
gravity, at least 'somewhat, anyway'.

this is the saw, or at least 'most of it' anyway
http://machines.2x.nu/unisaw_offloading/


if I lift the saw, and try 'balancing' it on, say, .500 diam round steel
rods, and find the 'balance center' left to right, then (use same
procedure to) find the balance center front to rear, is the center of
gravity ALWAYS over where the two lines intersect?

umm, it 'seems to me' like it is, but just checking here...

thanks guys,

toolie, of 'strange machine dollies' fame :-)

finding the center of gravity...(machine dolly-design related)
 

"dave" wrote in message
...
need to build a (retractable wheels) dolly for my big saw. the huge motor,
and other thick cast iron parts, stick out to one side, and rearward. I'd
prefer to space the wheels 'relative to' the center of gravity, at least
'somewhat, anyway'.

this is the saw, or at least 'most of it' anyway
http://machines.2x.nu/unisaw_offloading/


if I lift the saw, and try 'balancing' it on, say, .500 diam round steel
rods, and find the 'balance center' left to right, then (use same
procedure to) find the balance center front to rear, is the center of
gravity ALWAYS over where the two lines intersect?

umm, it 'seems to me' like it is, but just checking here...

thanks guys,

toolie, of 'strange machine dollies' fame :-)

Yes

finding the center of gravity...(machine dolly-design related)
 

On Sat, 05 Sep 2009 14:08:35 -0400, dave
wrote:

need to build a (retractable wheels) dolly for my big saw. the huge
motor, and other thick cast iron parts, stick out to one side, and
rearward. I'd prefer to space the wheels 'relative to' the center of
gravity, at least 'somewhat, anyway'.

this is the saw, or at least 'most of it' anyway
http://machines.2x.nu/unisaw_offloading/


if I lift the saw, and try 'balancing' it on, say, .500 diam round steel
rods, and find the 'balance center' left to right, then (use same
procedure to) find the balance center front to rear, is the center of
gravity ALWAYS over where the two lines intersect?

umm, it 'seems to me' like it is, but just checking here...

Yes.

Consider it from the other direction: imagine the object balanced on
a ball under its CG. If the ball is replaced with a rod, the object
will still be balanced in a direction perpendicular to the rod's axis.

finding the center of gravity...(machine dolly-design related)
 

Your method is perfectly correct but leaves out a very important issue;
how HIGH is the CG? Anything with a high CG needs to have a wider stance.

Consider a piece of machinery with 24" square base and the CG 2/3rds of
the way in both direction. If the height of the CG is 2" off the floor,
there is no way it will tip over. If the height of the CG is 36" off the
floor, if the machine tips slightly, over it goes. Actually, it is
pretty close to tan(distance from support/height) so tan^-1 (8"/36") is
only 12 degrees of tip before it crashes to the floor.

Swivel casters only make it worse: when the caster is swiveled to the
center, the load point moves quite a bit closer to the center. With a
common 3" iron caster wheel (like I use), the example above will tip
with less than 10 degrees of tilt.

Makes it a b****h to push it across a rough floor.

dave wrote:
need to build a (retractable wheels) dolly for my big saw. the huge
motor, and other thick cast iron parts, stick out to one side, and
rearward. I'd prefer to space the wheels 'relative to' the center of
gravity, at least 'somewhat, anyway'.

this is the saw, or at least 'most of it' anyway
http://machines.2x.nu/unisaw_offloading/


if I lift the saw, and try 'balancing' it on, say, .500 diam round steel
rods, and find the 'balance center' left to right, then (use same
procedure to) find the balance center front to rear, is the center of
gravity ALWAYS over where the two lines intersect?

umm, it 'seems to me' like it is, but just checking here...

thanks guys,

toolie, of 'strange machine dollies' fame :-)

finding the center of gravity...(machine dolly-design related)
 

dave wrote:

need to build a (retractable wheels) dolly for my big saw. the huge
motor, and other thick cast iron parts, stick out to one side, and
rearward. I'd prefer to space the wheels 'relative to' the center of
gravity, at least 'somewhat, anyway'.

this is the saw, or at least 'most of it' anyway
http://machines.2x.nu/unisaw_offloading/


Are you going to have an extension table? If so, extend the base of your dolly to cover
both and most of your tippy issues are solved.

My 20" bandsaw on a dolly is only moved slowly and after sweeping the floor first.


Wes

finding the center of gravity...(machine dolly-design related)
 

On Sep 5, 2:08*pm, dave wrote:
need to build a (retractable wheels) dolly for my big saw. the huge
motor, and other thick cast iron parts, stick out to one side, and
rearward. I'd prefer to space the wheels 'relative to' the center of
gravity, at least 'somewhat, anyway'.

this is the saw, or at least 'most of it' anywayhttp://machines.2x.nu/unisaw_offloading/

if I lift the saw, and try 'balancing' it on, say, .500 diam round steel
rods, and find the 'balance center' left to right, then (use same
procedure to) find the balance center front to rear, is the center of
gravity ALWAYS over where the two lines intersect?

umm, it 'seems to me' like it is, but just checking here...

thanks guys,

toolie, of 'strange machine dollies' fame :-)

If you hang something from a point the CG will be on a
line directly under that. Do this from another point and
the GC will be where the two lines cross.

This shows where the CG is in 3 dimensions but may
be difficult to do.