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Re: SRSG - rotor attachment

Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi David,

I was away from emails a couple of days. Scott has described the engagement of bushing to shaft very well.

Scott mentioned the pulleys end flanges could be machined off. This is true (the "V" which the belt rides in). In my case, I didn't go to that extreme. I simply drilled 3 holes spaced evenly through the "V". I used grade 8 bolts and mounted disc to the pulley. Whenever I want to remove the disc from the assembly, I simply remove the 2 hex bolts from the bushing (the 2 bolts used to compress the pulley onto the bushing) and insert them into the pre-drilled 1/4-20 holes in the bushing. As I tighten the bolts into the holes, they push the pulley off of the bushing. The bushing then simply slides off the shaft and the pulley-disc assembly is free to be removed.

To install the disc, I put the pulley-disc assy onto the shaft (sitting there loosely), then insert the bushing onto the shaft. I then slide the pulley-disc assy onto the bushing and remove the two 1/4-20 hex bolts from their removal holes and insert them into the "through-holes" of the bushing. I spin the disc by hand to align the 1/4-20 holes in the pulley with the bolts and begin screwing them into the holes. As I tighten the bolts, the pulley is pulled tighter and tighter onto the bushing tapered area. The bushing taper then is compressed onto the shaft as the bolts pull the pulley onto the bushing (yes, the pulley tapered hole is such that it compresses the bushing taper), and as Scott mentioned, with a great deal of force.

It's actually very simple once you have one in your hands. I know Scott explained it well, but I thought I should state my assembly for hopefully, added clarity.

Take care,

Tesla list wrote:

Original poster: "Scott Hanson" <huil888@xxxxxxxxxxxx>

David -

Yes, the pulley only has only two functions:
1. It provides the "female" taper that the split taper bushing is forced into to cause the bushing to contract slightly and thereby grip the motor shaft; 2. It provides the tapped holes for the bolts that are uesd to pull the two tapers together. The part of the pulley that actually was intended to engage the vee-belt is not used and could be machined off.

As the three bolts are tightned, the split taper bushing is gradually pulled into the bore of the pulley or sprocket; I'll call it a "hub" from now on.). As the nested tapers on the OD of the bushing and the ID of the hub are forced together, the hub tries to expand, and the split bushing tries to contract. The hub is solid and cannot expand, but the bushing is slotted ("split") and gets squeezed closed slightly, gripping the motor shaft. The "load" (in our case, the RSG disk) is supposed to be connected (bolted) to the the hub, not to the flange on the split bushing.

Many different companies manufacture "split taper bushings", but Browning is one of the largest. The Browning (Emerson Power Transmission) website has some clear illustrations showing exactly how the couplings work, but you must register on the website to get access to the data, and then search very carefully to find what you are looking for.

1. First, go to the website at www.emerson-ept.com
2. Fillout the information needed to "register"
3.Once you are setup with login and password, enter the website
4. Click the "Product Literature" icon at the bottom of the page
5. Enter "taper bushing" in the search box and click "GO"
6.A list of documents will appear; you want document #12, "Browning Mounting Instructions For Split Taper Bushings (Form 4013)".

This shows how the split taper bushing and the hub fit together, and how this assembly fits on the motor shaft. You'll notice that many of the split bushings have six holes in the flange, three through-holes, and three tapped holes. The through-holes are used for the bolts that pull the bushing and hub together; the bolts are removed and re-installed in the tapped holes to force the tapers apart when you want to remove the bushing & hub from the motor shaft.

Assembled with the correct parts, the split taper bushing is an extremely strong coupling, and can grip a shaft with thousands of pounds of force and transmit tens of thousands of foot-pounds of torque.

Scott Hanson

----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Tuesday, May 16, 2006 10:00 AM
Subject: Re: SRSG - rotor attachment

Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>

Hi all,

I am gonna have to show my ignorance here because if
"you don't ask, you won't know". I have been getting a
bit of a scolding for improperly mounting a split taper
bushing to my motor shaft to hold my RSG disc in place.
I've heard reference to using a pulley with the bushing to
properly attach the bushing and cause it to crimp down
on the shaft. I am having trouble picturing how the addi-
tion of a pulley to this setup will make it a more secure
clamp fitting to the shaft.? Could someone please enlight-
en me? Does the pulley go on the "inside" shaft collar end
of the bushing where screwing down the hub face to the
pulley squeezes the tapered collar halves down onto the
motor's shaft? I'm not sure that I would go out and modifiy
my RSG to the "proper" setup as my "improper" setup
is still a much better than an arbor for attaching a bench
grinder wheel to a motor shaft as the holding mechanism
for the rotory disc, but I am curious. In case anyone missed
the way that I modified my split taper bushing to affix it
to the motor shaft, I simply drilled and tapped 2 holes in the
split shaft collar of the bushing and screwed the bushing collar
to the shaft via 2 setscrews. I'm being told that this is a danger-
ously ineffective way to secure the bushing collar to the shaft
and I can kind of see where this is not the designed way to
secure the bushing to the shaft, but I'm still having trouble picturing
how using a pulley with the bushing will make it "in specs" to the
way that it was designed. Could someone  please enlighten my
mechanically challenged mind? ;^\

David Rieben

----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Monday, May 15, 2006 2:25 PM
Subject: Re: SRSG - rotor attachment

Original poster: "Bob (R.A.) Jones" <a1accounting@xxxxxxxxxxxxx>


I am not a mechanical or power transmission engineer but using this method
without a hub to restrain the split ring assuming the mounting screw is on
one of the wings is a bad idea.
I doubt you need much more than rudimentary mechanical experience to
conclude this.
Defining what the expected skills of rudimentary mechanical experience is
could be tricky.
Perhaps not using a split ring in the way suggested is one of them.

Robert (R. A.) Jones
A1 Accounting, Inc., Fl
407 649 6400
----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Sunday, May 14, 2006 8:24 PM
Subject: Re: SRSG - rotor attachment

> Original poster: Mddeming@xxxxxxx
> Hi David, Scott,
> `    I fully agree that anyone building a TC is taking certain risks
> and coilers should consider this when engaging in the hobby. There
> are many intrinsic risks that are carefully pointed out in the safety
> pages on many of the members web sites and in the archives. Just as
> in extreme sports, to raise an alarm that it is in general, not safe
> is a disservice.
>      However,  when a piece of equipment or a technique is published
> worldwide to beginners as well as experienced participants as a
> recommended technique or device, then pointing out any possible
> structural/mechanical shortcomings is not only permissible, it's
> laudatory.  The problem is not in " a power transmission engineer's
> point of view" , it's the mechanical engineers who are groaning over
> this one. No one is saying you shouldn't use it or that it's not
> working for you, but any idea that is "broadcast" should be subjected
> to closer scrutiny. So, IMHO, "Thanks to you both!"
> Matt D.
> In a message dated 5/14/06 7:35:33 P.M. Eastern Daylight Time,
> tesla@xxxxxxxxxx writes:
> Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>
> Hi Scott,
> I wouldn't even try to argue with you about whether or not
> my setup is "conventional" or "risky" from a power transmission
> engineer's point of view. You're probably absolutely correct!
> I'm also sure it  wouldn't pass OSHA's standards, either! ;^0
> As far as that goes, I'm sure most electrical power engineers
> (except for maybe the ones on this list) :^)) would tell most, if
not > all,
> of us coilers that from a safety standpoint, our beloved Tesla coils > are
> "extremely risky and unconvetntional", too, even with all of the
> proper dedicated RF grounding, line filtering, ect. I'm sure an OSHA > > rep > would have "heart failure" if he were to look at the setup of most of > > our
> coils and would never allow for such an extremely hazardous contraption
> to be placed in a public display or an industrial occupational setting!
Why do
> you think that "Tesla coil" insurance is so exhorbitantly expensive,
> even for the "real"
> Tesla coil  "pros" like Jeff Parrise, Bill Wysock, or Greg Leyh when
> they are the ones
> who "really" know what they're doing? The way I see it, I'm
> not  running my RSG 24/7
> for weeks or months at a time, so I think in my situation, my split
> taper bushing
> being used "outside the box" of its intended use will serve my
> purposes just fine ;^)
> I WAS safe enough to built my RSG "inside of a Lexan box", though, to
> myself not only from a hub possibly  flying loose, but also from
> possible flying shards
> of tungsten, in case it were to fail in that particular manner.
> I think it all comes down to risk management. By the very fact that you
build a
> Tesla coil, you are taking on some risk, both mechanical and
> electrical, and probably
> other risks as well. There's just no way around that! If one cannot
> deal with this fact,
> then they just don't need to build a coil at all. End of story! For
> those of us who
> are willing to accept the risks involved with this hobby, what we try
> to do is to
> minimize the risk to acceptable levels. By building a Lexan box shield
> my RSG, I'm reducing the risk of possible injury due to possible
> failure of the RSG components to very acceptable levels. I am NOT
> the risk, but I AM greatly reducing it. The same goes for using
> proper line filtering,
> dedicated RF grounds, panel metering, ect. Some of us obviously go
> further to reduce
> the risks than others but obviously, we all practice a least some
> level of risk reduction
> since there seems to be remarkably few reported mishaps (at least
> mishaps that people
> are willing to admit to) ;^) Let's try to keep it that way ;^))
> David Rieben