Speed Rail and Bearings
Most of the time we want as much rigidity in a rig as we can obtain. Other times
we need a bearing to attach to pipe to allow something to move smoothly. A pipe
inside a Speed Rail, Key Klamp or scaffold cross or fitting is usually not smooth
or tight enough. The Speed Rail Adjustable Tee #17 can be used for lighter load
applications. The socket, not the through section, can be filed to make the
fitting adjust farther if you remove the pin. You can replace the pin with a
bolt and lock nut or ream the hole a bit larger and replace the pin with a larger
bolt. ONLY USE THIS FITTING FOR LIGHT LOAD BEARING APPLICATIONS.
The Kee Clamp #C50 Single Swivel Socket is stronger than the Speedrail # 17,
but the pin fit is quite sloppy. You can ream the holes out to 7/16" and use
a 7/16" bolt to replace the pin. Make sure that the bolt has no threads in the
bearing portion. This fitting can be bought in separate parts # F50 and #M50
in different pipe sizes and assembled together. 1-1/4",1-1/2" and 2" pipe sizes
are interchangeable. This fitting and the Speed Rail #17 are still not a true
bearings, but will satisfy many applications such as the crank dolly push rod
for a stage dolly. (See The Crank Dolly)
A bolt in a thread can become a useful bearing, The set screws holes in Speed
Rail fittings are too light for most applications, but taping a hole in a piece
of solid nylon, plastic or other material inside pipe diameter can provide a
strong, tight bearing. This should be done on a drill press or lathe to insure
a square hole. Do drill and then tap the piece without removing the piece from
the drill vice or lathe chuck to assure the tap aligns with the hole. You can
break a tap if not properly aligned in a hole.
Attaching ball bearings inside Speed Rail fittings usually becomes lathe work.
A 6 jaw chuck is very helpful for holding thin pieces of metal such as Speed
Rail fittings. You can sometimes find bearings that can be shimmed up to a pipe
size that can then be put into a fitting. Do not tightening a set screw on a
bearing, it will distort the bearing and make it useless. Turn the fitting to
fit the bearing snugly. Find a bearing that can be shimmed up to fit the fitting
or one that requires very little metal removal to keep the strength of the fitting.
You can make a fair bearing by turning the inside of a piece of plastic pipe
to a smaller pipe size O.D. DO NOT BREATH THE VAPOR FROM MACHINED PVC, IT IS
TOXIC. Often pipe is not very round. You can improve the shape by turning the
pipe down slightly until it is round and smooth on the lathe. Consider using
a Speed Rail cross with one side a next larger pipe size to give you more room
to work with.
Mounted bearings, such as on work arbors, can be attached to wall and floor
flanges with plywood or metal with holes and bolts. Rod end bearings (Hiem joints)
can be useful for push rods, because they are self aligning and tight. Both
flange and pillow block mounted bearings are very useful in pairs. They are
often quite heavy, but there are lighter duty styles that satisfy most of our
needs. I find that often the larger sizes of shaft are needed to mount rigs
on, but are often too heavy. Larger ring bearings and hollow tube make much
more rigid devices with less weight. These are not off-the-shelf items, but
can be found on the surplus market.
Always consider the load that you are trying to move. Make sure you are not
over loading Speed Rail fitting that are made originally for stationary railings.
Often you can counter balance a load with a counter weight or diagonal brace
to reduce the strain on a device.
When you build a bearing rig or any rig, think about how it can be modified
for a future application. It may be worth the effort and extra expense to make
Both front and back wheel vehicle bearing assemblies are very useful. Rear wheel
assemblies from front wheel drive cars are useful as are front wheel units from
rear wheel drive cars. I have used rear axles with their bearings in place (no
housing) by turning a collar to fit the bearing to 2" (2-3/8" OD) pipe. A piece
of plastic turned to fit over the differential spline to fit inside the pipe
works well. You can also shorten an axle and add another bearing. Consider using
the lug nuts and wheel to attach your rig. These aren't the most "professional
looking" rigs, but can work fine. You might even consider using the brake shoes
of rear wheel assemblies from front wheel drive cars. The emergency brake lever
will still work mechanically.
© Copyright 1999-2004 Ron Dexter. All Rights Reserved.