Pillow block shaft lock collar installation
Hovercrafters
pillow block bearings? I would also like to learn a good method for
removing them after.
Thanks,
Brendin
Ken Roberts
Brendin,
I always put them so the collar goes on BETWEEN the bearings, in case one comes
loose it will always stay with the craft.
So you loosely bolt the pillow blocks on the craft, stick the shaft part way
through and add a locking collar, the pulley assembly, the belt, the second
locking collar and then stuff the shaft through the second pillow block. I
leave the locking collars until absolutely last, so I put the prop on and center
everything in the duct. This is sort of involved too, if you have a proper
engine mount as in a UH-18sp or similar. The bottom shaft lines up with the
crank shaft, the top shaft is to tighten the belt and then the motor mount is
moved up and down as a whole to center the prop in the duct, and even side to
side by shimming one side higher than the other.
Get the belt tight and aligned at least close, then lock the pulley mountings
down. Get the prop where you want it in the duct (front to back), and then
lock the locking collars on.
Now we get to the part you were actually asking about.
The bearing has a sticking-out part on one side for the locking collar. The cam
(that's what it's called) is thicker on one side than on the other, it's a
circle that's off center from the shaft hole. The locking collar has the female
part of the same thing. You slip the collar over it and turn it to one side to
snug it down.
There's probably a correct direction to this. My own thought is that you
tighten it so that if you were holding the collar with your fingers and click
the starter, the turning of the shaft would cause the collar to tighten. It
probably doesn't make much difference, but it seems that's the safest route.
Next, you'll notice that there are at least two holes in the locking collar.
One is for a set screw, the other only goes part way through. Take a center
punch or nail set (or screwdriver if you have a disposable one) and a hammer and
use the OTHER hole (not the one with threads) to tap the locking collar on
tighter. This collar will take the entire thrust load of the hovercraft, so
make it snug. Double check to be sure the set screw won't come in contact with
the key channel before you screw it down.
Hovercrafters
"Ken Roberts" <k...@kroberts.in.9ci.com> wrote in message
news:slrnd5aul...@kroberts.in.9ci.com...
DHy...@students.wisc.edu
Ken Roberts wrote:
> The bearing has a sticking-out part on one side for the locking
collar. The cam
> (that's what it's called) is thicker on one side than on the other,
it's a
> circle that's off center from the shaft hole. The locking collar has
the female
> part of the same thing. You slip the collar over it and turn it to
one side to
> snug it down.
This really puzzled me when I first opened up my drive kit and looked
at my bearings: it seems at first glance like they made a mistake and
bored the hole off-center.
Dan
Ken Roberts
this stuff out.
Dave Schneider
I ended up busting the lock collars trying to get them off. That was ok
though, because I was replacing the bearings anyway.
"Hovercrafters" <you....@spammersgotohell.com> wrote in message
news:8se5e.6061$VF5.2492@edtnps89...
Marquis Songer
twist. It's worked very well for me. Just make sure you remember to back
out that set screw first.
Marquis Songer
"Dave Schneider" <schne...@hotmail.com> wrote in message
news:d342d2$17pf$1...@si05.rsvl.unisys.com...
Gordon McAndrew
One thing to do is to standardize the direction you turn the collar to
tighten or loosen. I use the saying lefty loosey, righty tighty. In other
words turn the collar to the right as you look at it to tighten it. Then
you just have to bang on it to the left or counterclockwise to loosen it.
I had four to recover from the shafts that were on my large hovercraft and
only had to give them each one solid whack to get the collar off.
Gordon McAndrew
"Hovercrafters" <you....@spammersgotohell.com> wrote:
;>Can someone tell me the proper way to install the shaft lock collar on my
;>
Dave Schneider
"Marquis Songer" <marqui...@hovercraft.com> wrote in message
news:82n5e.1134$qS4....@fe2.columbus.rr.com...
jarrob
"Hovercrafters" <you....@spammersgotohell.com> wrote in message
news:8se5e.6061$VF5.2492@edtnps89...
The correct way to install the eccentric locking collar is NOT to tighten it
onto the bearing (at least according to the manufacturer who must know
something about it ;-)!
All you need to do is slide the collar up so it fits over the bearing snugly
then tighten the locking grub screw. When the shaft rotates the inner
bearing it locks itself into the locking collar with the minimum force
required to prevent the bearing rotating on the shaft. If you tighten the
collar using a wrench or a punch then you can distort the bearing, shaft, or
collar (I'm talking from direct experience here :-(.
The main purpose of the locking collar is to prevent the shaft sliding
lengthways out of the bearing (the grub screw is the device used to stop
this). The eccentric locking cams are just there to prevent the inner
bearing case rotating on the shaft - you need very little force to stop
this rotation (unless the bearings are seized!).
You will find it much easier to remove the collars if you don't try to
tighten them - they are simply removed using a tap or punch in the direction
opposite to the shafts normal rotation (for example, if the shaft turns
clockwise then tap the collar anti clockwise).
Ken Roberts
them off. Maybe if you don't do that, you could etch an arrow with "off"
written on it right on the collar.
Ken Roberts
Really?
Have you tried this on a thrust prop? In the case of a thrust prop, the locking
collar is all that prevents the thrust of the hovercraft (several hundred
pounds) from pushing the shaft forward. In other words, the bearings are taking
the full force of thrust and the locking collars are what allows this.
I'm a bit skeptical that your technique is going to work in this case.
jarrob
Hi Ken,
I know it sounds odd but it is what the pillow block manufacturers say - I
quote "The assembly to the shaft is done only by tightening the eccentric
collar to the shaft by use of the setscrew. The revolving force of the
shaft is utilized as the tightening force".
They also specify that for large thrust loads you should either use a
shoulder on the shaft OR provide a location indent for the setscrew. The
other important thing to note is that you should not lock more than one
bearing onto each shaft - when differential thermal expansion occurs in the
shaft, bearing mount or frame the increase in thrust load can damage or
destroy a bearing or housing.
I now have to admit I did it all wrong when I built my UH18! I originally
used eccentric locking collars on my UH18 and the bearings failed after only
about 100 hours of use. I had locked all of them by tightening the locking
collar as you describe. The bearing seats themselves were worn and I had
also cracked a couple of pillow blocks (thermal expansion perhaps?).
I have to admit I was also sceptical (UK spelling?) of relying on a grub
screw to take the thrust load so I fitted a short pipe sleeve over the
thrust shaft between the prop hub and the rear bearing to transfer the
thrust directly to the bearing itself (a single 35mm or 1 3/8" bearing is
designed to take a thrust load far in excess of the feeble amount the prop
generates!) This bearing has a maximum thrust load of 1012Kgf (the cast
housing can take 2400Kgf) - the typical prop thrust is unlikely to exceed
200Kgf.
Ken Roberts
>
> "Ken Roberts" <k...@kroberts.in.9ci.com> wrote in message
Wow.
That seems just plain unnatural.
I've been using two locking collars on my 12r, but frankly that's a wood
structure that has seen better days. There's probably more than enough flex
in the wood to allow for thermal expansion.
The sleeve between the hub and the bearing seems like a really good idea. I'll
try that on my 18. That would, of course, mean that the rear bearing is the one
that takes the thrust.
Thanks for your input. I would never have guessed this stuff.
Pannawonica
have you thought about drilling a dimple into the shaft
so that the grub screw has something to locate into
this will aid the collar locking.
if there's more than one grub screw then it should be
dimpled also.
a spacer tubes between the bearings and the pulley will
also add further strength to the assembly.
its a common practice in engineering.
Pannawonica ..
Terry
with the locking collar self tightening with the rotation. The place I
bought the bearings from said that anyway. Also if you dimple the shaft
for the set screw before ya put it in clean it (oiled for delivery) and
use some thread lock on it, just what I did they seem to like to come
loose ;-), Also I have used a gear puller to get them off. But I like
the pipe wrench idea, thanx
TT