I hate swivel casters on one end of a dolly when the load is real
*heavy*. they're ok when the load is light but when the dolly is HEAVY,
it's OK going straight in one direction, but IMPOSSIBLE to get turned
around unless you either jack up one end of the cart and turn the
steering casters by hand OR you "have a spare mile or so" of room to
maneuver. and space availability in my garage is 'far less than optimal'

so I want to convert some 'normal' swivel casters (have tons of 'em) to
'ackerman steer' casters. I need two stout acker-dollies: one to hold my
dialarc (with other stuff piled on top of it) and another dolly for my
500 lb table saw.

-----------------------------
anybody here ever tried this?
-----------------------------

I'm pretty sure it can be done by welding 'ackerman ears' to the tops of
the forks of 'normal' swivel casters. a little bizarre, perhaps, but
workable. put it this way: the geometry seems to work in the mockup I
made (and illustrated) he

http://bubba.hostrator.com/ackerman_...rs_conversion/

comments invited :-)

thanks,

toolie dave

ps-I'm familiar with the 'running gear' miller sells for this welder,
with its' a
href="http://freemanracing.com/home/components/com_virtuemart/shop_image/product/ca2435dd117737d6bee9ae138f447dbf.jpg""kid's
wagon" type steering/a, and I think this ackerman-mod idea is better.
I realize having swivel casters with "no trail" would be better, but, I
might cut mine and reweld them "straight-forked", OR just "leave the
forks like they are now", but with their newly-attached ears. well, let
me know :-)

- -
replies by e-mail, if any, please remove the weirdstuff from my address
before you click 'send'. thanks :-)
- -

Technically speaking, you do not have true Ackerman steering unless the
outside wheel does not turn to as sharp an angle as the inside. This is
the way to make the two steering casters move to the different radius
turns.

As long as the distance from the tongue pivot pin to the drag link is
the same as the distance from the caster pivot to it's drag link hole
AND the drag link is straight to start, you will have decent turning but
not exact turning.

there are a couple ways to get the correct geometry: first is to make
the pivot points for the caster draglinks offset from the line of travel
to the INSIDE. The offset angle and length are both critical. You can
also move the drag link center point forward(?)to get close but not exact.

dave wrote:
I hate swivel casters on one end of a dolly when the load is real
*heavy*. they're ok when the load is light but when the dolly is HEAVY,
it's OK going straight in one direction, but IMPOSSIBLE to get turned
around unless you either jack up one end of the cart and turn the
steering casters by hand OR you "have a spare mile or so" of room to
maneuver. and space availability in my garage is 'far less than optimal'

so I want to convert some 'normal' swivel casters (have tons of 'em) to
'ackerman steer' casters. I need two stout acker-dollies: one to hold my
dialarc (with other stuff piled on top of it) and another dolly for my
500 lb table saw.

-----------------------------
anybody here ever tried this?
-----------------------------

I'm pretty sure it can be done by welding 'ackerman ears' to the tops of
the forks of 'normal' swivel casters. a little bizarre, perhaps, but
workable. put it this way: the geometry seems to work in the mockup I
made (and illustrated) he

http://bubba.hostrator.com/ackerman_...rs_conversion/

comments invited :-)

thanks,

toolie dave

ps-I'm familiar with the 'running gear' miller sells for this welder,
with its' a
href="http://freemanracing.com/home/components/com_virtuemart/shop_image/product/ca2435dd117737d6bee9ae138f447dbf.jpg""kid's
wagon" type steering/a, and I think this ackerman-mod idea is better.
I realize having swivel casters with "no trail" would be better, but, I
might cut mine and reweld them "straight-forked", OR just "leave the
forks like they are now", but with their newly-attached ears. well, let
me know :-)

- -
replies by e-mail, if any, please remove the weirdstuff from my address
before you click 'send'. thanks :-)
- -

Dave.
I built two heavy duty carts with fixed casters on one end and
swivels on the other. On the steering end was a strong T-handle of
one and 1/2 inch pipe. The handle was hinged at wide spaced pivots
so it could go up and down but not sideways so it was a good steering
lever. On level concrete it could carry three tons without much
trouble.
If the swivel casters got confused, rowing on the T-handle would get
things going. The pivots were set low so the handle could be used
as a pry-bar to get over curbs with light loads and johnson bars
helping
in the back. The low pivots allowed storing the handle under the cart
when huge things were carried. The back wheels were 6 inch steel
that may have come from a bridge crane with no flanges. The front
casters were 4 and 1/2 inch with cushion tires. I think casters would
be much more maneuverable than an ackerman setup. The key point
with casters was to have a good steering handle. Since the handle did
not pivot sideways long beams could hang way out on both ends and
not bother the steering. The carts (2) were about two and 1/2 feet by
four.
For humongus loads the non-steering ends could be clamped together
to make one big cart that pivoted about the middle.

Best regards, Charlie


On Jan 10, 6:20*pm, dave wrote:
I hate swivel casters on one end of a dolly when the load is real
*heavy*. they're ok when the load is light but when the dolly is HEAVY,
it's OK going straight in one direction, but IMPOSSIBLE to get turned
around unless you either jack up one end of the cart and turn the
steering casters by hand OR you "have a spare mile or so" of room to
maneuver. and space availability in my garage is 'far less than optimal'

so I want to convert some 'normal' swivel casters (have tons of 'em) to
'ackerman steer' casters. I need two stout acker-dollies: one to hold my
dialarc (with other stuff piled on top of it) and another dolly for my
500 lb table saw.

-----------------------------
anybody here ever tried this?
-----------------------------

I'm pretty sure it can be done by welding 'ackerman ears' to the tops of
the forks of 'normal' swivel casters. a little bizarre, perhaps, but
workable. put it this way: the geometry seems to work in the mockup I
made (and illustrated) he

http://bubba.hostrator.com/ackerman_...rs_conversion/

comments invited :-)

thanks,

toolie dave

ps-I'm familiar with the 'running gear' miller sells for this welder,
with its' a
href="http://freemanracing.com/home/components/com_virtuemart/shop_image/pr...""kid's
wagon" type steering/a, and I think this ackerman-mod idea is better.
I realize having swivel casters with "no trail" would be better, but, I
might cut mine and reweld them "straight-forked", OR just "leave the
forks like they are now", but with their newly-attached ears. well, let
me know :-)

- -
replies by e-mail, if any, please remove the weirdstuff from my address
before you click 'send'. * * * * * * * * * * * * * * * * * * thanks :-)
- -

RoyJ wrote:
make
the pivot points for the caster draglinks offset from the line of travel
to the INSIDE. The offset angle and length are both critical.

According to some texts, the angle is described as one line from wheel
centre to pivot, other line from pivot to centre of rear axle.
- No mention of lengths.

Jordan

wrote in message
...
Dave.
I built two heavy duty carts with fixed casters on one end and
swivels on the other. On the steering end was a strong T-handle of
one and 1/2 inch pipe. The handle was hinged at wide spaced pivots
so it could go up and down but not sideways so it was a good steering
lever. On level concrete it could carry three tons without much
trouble.
If the swivel casters got confused, rowing on the T-handle would get
things going. The pivots were set low so the handle could be used
as a pry-bar to get over curbs with light loads and johnson bars
helping
in the back. The low pivots allowed storing the handle under the cart
when huge things were carried. The back wheels were 6 inch steel
that may have come from a bridge crane with no flanges. The front
casters were 4 and 1/2 inch with cushion tires. I think casters would
be much more maneuverable than an ackerman setup. The key point
with casters was to have a good steering handle. Since the handle did
not pivot sideways long beams could hang way out on both ends and
not bother the steering. The carts (2) were about two and 1/2 feet by
four.
For humongus loads the non-steering ends could be clamped together
to make one big cart that pivoted about the middle.

Best regards, Charlie


On Jan 10, 6:20 pm, dave wrote:
I hate swivel casters on one end of a dolly when the load is real
*heavy*. they're ok when the load is light but when the dolly is HEAVY,
it's OK going straight in one direction, but IMPOSSIBLE to get turned
around unless you either jack up one end of the cart and turn the
steering casters by hand OR you "have a spare mile or so" of room to
maneuver. and space availability in my garage is 'far less than optimal'

so I want to convert some 'normal' swivel casters (have tons of 'em) to
'ackerman steer' casters. I need two stout acker-dollies: one to hold my
dialarc (with other stuff piled on top of it) and another dolly for my
500 lb table saw.

-----------------------------
anybody here ever tried this?
-----------------------------

I'm pretty sure it can be done by welding 'ackerman ears' to the tops of
the forks of 'normal' swivel casters. a little bizarre, perhaps, but
workable. put it this way: the geometry seems to work in the mockup I
made (and illustrated) he

http://bubba.hostrator.com/ackerman_...rs_conversion/

comments invited :-)

thanks,

toolie dave

ps-I'm familiar with the 'running gear' miller sells for this welder,
with its' a
href="http://freemanracing.com/home/components/com_virtuemart/shop_image/pr...""kid's
wagon" type steering/a, and I think this ackerman-mod idea is better.
I realize having swivel casters with "no trail" would be better, but, I
might cut mine and reweld them "straight-forked", OR just "leave the
forks like they are now", but with their newly-attached ears. well, let
me know :-)

- -
replies by e-mail, if any, please remove the weirdstuff from my address
before you click 'send'. thanks :-)
- -


Put bigger fixed casters in the middle and swivel casters on the end. Then
you can steer by just swiveling around the middle casters.

On Jan 10, 10:35*pm, "Calif Bill" wrote:
wrote in message
On Jan 10, 6:20 pm, dave wrote:
...
so I want to convert some 'normal' swivel casters (have tons of 'em) to
'ackerman steer' casters. I need two stout acker-dollies: one to hold my
dialarc (with other stuff piled on top of it) and another dolly for my
500 lb table saw.

-----------------------------
anybody here ever tried this?
-----------------------------

Put bigger fixed casters in the middle and swivel casters on the end. Then
you can steer by just swiveling around the middle casters.

That works very well but I think it would be too wobbly and dangerous
for a table saw. My lighter table saw is on casters attached to hinged
plates that fold underneath so it rests solidly on the ground when I
use it.

This is how I modified my shop crane to roll outdoors:
http://picasaweb.google.com/KB1DAL/W...51034176921634

You shouldn't need to add the extra wheels if you stay on pavement. I
tow that thing through the woods to lift logs and boulders. The jack
is in close for strength and it has to be cranked up to swivel. You
could mount it further out for better clearance. That end of the saw
could rest on fixed feet.

I put a lot of effort into designing Ackermann steering for a
hydraulic scissors table. Ultimately it got a fixed axle that clips
under two hooks on one end and a trailer hitch coupler on the other,
to use with this home-made handle:
http://picasaweb.google.com/KB1DAL/W...63513288463986

There is a similar arrangement used industrially. The pallet has a
flat horizontal tongue with a hole, the wheeled handle a short lever
with an upright pin. Mine needs more lift because I use it outdoors so
the hinged hook raises the coupler off the ground, then I kick a wood
block under it and raise it the rest of the way with the ball.

Instead of welding on tabs, why not replace the axles and fit the
linkage forks onto them?

Jim Wilkins

It's been a while since I've done the calcs. The necessary difference in
angle from side to side is a function of the wheelbase also. The OP
wanted to have the tongue be in line with the direction of motion which
adds another item to the equation.

Jordan wrote:
RoyJ wrote:
make the pivot points for the caster draglinks offset from the line of
travel to the INSIDE. The offset angle and length are both critical.

According to some texts, the angle is described as one line from wheel
centre to pivot, other line from pivot to centre of rear axle.
- No mention of lengths.

Jordan

What's that Lassie? You say that dave fell down the old
rec.crafts.metalworking mine and will die if we don't mount a rescue
by Sat, 10 Jan 2009 18:20:09 -0500:

so I want to convert some 'normal' swivel casters (have tons of 'em) to
'ackerman steer' casters. I need two stout acker-dollies: one to hold my
dialarc (with other stuff piled on top of it) and another dolly for my
500 lb table saw.

That won't be true ackerman, but might be good enough.
See: http://en.wikipedia.org/wiki/Ackerma...ering_geometry
for a good graphic on how the pivot points on the castors will
converge at the same point along the rear wheel axis.

--

Dan H.