HP-Agilent-Keysight-equipment@groups.io

Re: opertunity to have uWaveEngineer1968 test his gear hobber - 8640B for $1

J Forster

OT:  (So what else is new...   LoL)

I recently visited Battleship Cove in Fall River, Massachusetts and toured the ships there.  (Well worth the trip, BTW)

There was ANOTHER way of making a corner gear. It was used on a valve on the destroyer Joseph Kennedy. There were two
disks, one on each shaft, and two rings of nubs, like 1/2 steel balls, attached one to each disk. The balls from one disk
intermeshed with those on the other, forming a corner gear.   Really funky, but it worked.

Best,
-John

Chuck Harris wrote:

Show quoted text

You can't do a decent job of cutting a bevel gear on a mill.  To quote
Machinery's Handbook:

"Cutting Bevel Gear Teeth - A correctly formed bevel gear tooth has the same
sectional shape throughout its length, but on a uniformly diminishing scale from the
large to the small end.  The only way to obtain this correct form is by using a gener-
ating type of bevel gear cutting machine.  This accounts, in part, for the extensive use
of generating type gear cutting equipment in the production of bevel gears. [snip]

Re: opertunity to have uWaveEngineer1968 test his gear hobber - 8640B for $1

#8987

Yes, but with a mill cut bevel gear, you can feel
every tooth meshing and unmeshing.  It feels like a
really buggered up gear.  It might not matter for a
switch, though, but isn't that beveled gear set something
a little more exotic than just a switch turner?

-Chuck

lothar baier wrote:

Show quoted text

well, it was a thought !
  keep in mind that we are not talking about high speed or precission gears here

Re: opertunity to have uWaveEngineer1968 test his gear hobber - 8640B for $1

lothar baier

#8985

the problem with parts mules is that you really dont know if the unit you get doesnt have the same problem and if it doesnt how long the part will last   

Chuck Harris <cfharris@...> wrote:          Bob Groschen wrote:

Show quoted text

----- Original Message ----- 
From: "John Miles" <jmiles@...>
To: <hp_agilent_equipment@...>
Sent: Thursday, November 08, 2007 1:57 PM
Subject: RE: [hp_agilent_equipment] Re: opertunity to have uWaveEngineer1968 
test his gear hobber - 8640B for $1

I'm sure that if someone actually does the work and offers a full set of
good-quality 8640 gears for $50 or less, the customers will be there. At
least one, anyway! (raises hand) At $100 or more you are competing with
parts-mule prices, so it doesn't make as much sense to create new gears if
that's what it would cost.This is precisely the problem with Chuck's proposal. If one *has* the
parts mule generator, then one has the gears needed. Natural priority
is to repair your generator first and worry about finding the off-the-shelf
equavilents later.Tis fine with me. One day, you will want some gears,
and there won't be any more parts mules available.

I prefer to plan for the future, rather than eat the
seed.

But then I don't have a dog in this race. I was just
trying to be nice.

-Chuck Harris

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Re: opertunity to have uWaveEngineer1968 test his gear hobber - 8640B for $1

#8984

The big multi kilowatt machines are good for making
really big parts.  But we are just making a tiny gear.
You can handle a job like this with a diode, a light bulb,
and a small electrolytic capacitor.  I have seen it done
on a modified drill press.  The accurate slow feed is
the trickiest part.

We only need to make one female injection mold using EDM,
not a production run of parts.

-Chuck

lothar baier wrote:

Show quoted text

i remember years and years ago we had a similar problem with another plastic part, we used a part sprayed graphite on
it and then plated over a layer of copper, this served as a EDM tool, problem was we had to make 3 of them because
they wore out. most EDMs i looked at have 3 parts, the machine itself, a power supply and a pump that circulates and
filters the dielectric fluid, i havent seen a machine with a 50W supply, even the smallest ones are in the KW range,
dont know why they use 3 phase , im not the guy who designed the machine, my guess is that it is better in large
shops where you have numerous machines to distribute the load , i dont know ! check ebay under hansvedt, there is
stuff out there, i have a 19x19ft two story shop, right now filled with the gear hobber, a large floor drill press,
lathe, grinder and some work benches, what i really desire right now is a mill and a surface grinder

Re: opertunity to have uWaveEngineer1968 test his gear hobber - 8640B for $1

lothar baier

#8982

initial setup takes about 45-60minutes you are right on that, this is a one time operation, then put a stack of blanks on and hob them, change the stack and hob the next batch, the time to change the batch is about 5minutes tops, so lets do the math:
   
  10minutes hobbing time per batch
  +
  5minutes changing time per batch  = 15minutes per batch 
  60/15 = 4batches per hour * 5gears in a batch  = 20gears per hour
   
  2hrs/20gears/hr=6minutes per gear if you machine 1 batch
  3hrs/40gear/hr=4.5minutes per gear if you make 2 batches  and so on 
   
   

Chuck Harris <cfharris@...> wrote:
          lothar baier wrote:
still trying to figure out where you get the hour for hobbing the gear from !Does your machine set itself up as you change gear types?

As I said, one gear will take a couple of hours to make, there
is some economy of scale, but you are unlikely to want to cut
more than ten gears in a production run.

....

those are small parts with fairly large DP in soft material, according to some preliminary calculations based on
delrin and my machine handbook it should take about 10-15minutes to hob 1gear !

The biggest challenge in casting is to get airpockets out, one way is to use a cylinder to push the epoxy into the
form until the material overflows out of a second hole, or you can put the form on a vibrator to achieve this, im not
an expert but i have seen some castings done and thats how they did it.You use very thin epoxy casting compounds. They flow very nicely.
Once they are in the mold, you hit the vacuum, and draw the bubbles
out for a perfect fill.

-Chuck Harris


                         

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Re: opertunity to have uWaveEngineer1968 test his gear hobber - 8640B for $1

J Forster

#8980

Actually, making an EDM attachment for a milling machine is really quite easy.  Some years ago, I wanted to get into the
guts of a microwave oven to modify it for other uses and it was buttoned up with Torx No-Tamper screws. I could not get the
appropriate drivers anywhere (now they are easily available) so built up an EDM setup. It was not the fastest thing in the
world, but did cut the super hard steel very well with high precision.

Chuck, I'm sure you could cobble up a similar setup in an afternoon or two. There is no problem if you feed very slowly,
except the production rate is low. Doing this eliminates the need for FB loops on the axes.

Best,
-John




Chuck Harris wrote:

Show quoted text

Hi Lothar,

The electrode could be something as fancy as a CNC made
graphite model, or it could be something as simple as
adding a little plating to the original plastic gear.

There is no intrinsic reason that an EDM machine should
need 3 phase power, the power requirements for one that
could handle a part this size are very modest... well under
50 watts.

I generate my own 3 phase in my shop.  It is easy to do,
and all you need is a big 3 phase motor, and some simple
control components to get it started.

As John said, a silicone mold of the original gear would
be the easiest way.... Damn!.. I wanted an EDM machine.

-Chuck Harris

lothar baier wrote:
i was eyeballing a EDM for a bit but unfortunatly dont have enough floorspace right now, another problem is that most
EDMs require 3phase current which i dont have out here. There are some benchtop type hansved edms on ebay every once
in a while. Another issue it that you need to have a electrode that resembles the form of the gear made of graphite
or copper and usually those are CNC machined parts

Yahoo! Groups Links

Re: opertunity to have uWaveEngineer1968 test his gear hobber - 8640B for $1

#8981

Bob Groschen wrote:

Show quoted text

----- Original Message ----- 
From: "John Miles" <jmiles@...>
To: <hp_agilent_equipment@...>
Sent: Thursday, November 08, 2007 1:57 PM
Subject: RE: [hp_agilent_equipment] Re: opertunity to have uWaveEngineer1968 test his gear hobber - 8640B for $1

I'm sure that if someone actually does the work and offers a full set of
good-quality 8640 gears for $50 or less, the customers will be there.  At
least one, anyway!  (raises hand)  At $100 or more you are competing with
parts-mule prices, so it doesn't make as much sense to create new gears if
that's what it would cost.This is precisely the problem with Chuck's proposal.  If one *has* the
parts mule generator, then one has the gears needed.  Natural priority
is to repair your generator first and worry about finding the off-the-shelf
equavilents later.Tis fine with me.  One day, you will want some gears,
and there won't be any more parts mules available.

I prefer to plan for the future, rather than eat the
seed.

But then I don't have a dog in this race.  I was just
trying to be nice.

-Chuck Harris

Re: opertunity to have uWaveEngineer1968 test his gear hobber - 8640B for $1

#8979

You are, of course right, but letting the experts do their
thing will quickly put the gears out of reach of everyone that
truly needs them.

People that can afford the experts, don't need 8640B's.

-Chuck Harris

J Forster wrote:

Show quoted text

IMO, that's the really hard way to do it!! I'd measure the gears and
write a simple spec and have the experts do it, or failing that, cast it
out of filled epoxy resin in a Si rubber mold. See what I just posted on
that issue. There are companies that do such castings as a business.
Best,
-John

Re: opertunity to have uWaveEngineer1968 test his gear hobber - 8640B for $1

lothar baier

#8978

well, it was a thought !
  keep in mind that we are not talking about high speed or precission gears here
     

Chuck Harris <cfharris@...> wrote:
          You can't do a decent job of cutting a bevel gear on a mill. To quote
Machinery's Handbook:

"Cutting Bevel Gear Teeth - A correctly formed bevel gear tooth has the same
sectional shape throughout its length, but on a uniformly diminishing scale from the
large to the small end. The only way to obtain this correct form is by using a gener-
ating type of bevel gear cutting machine. This accounts, in part, for the extensive use
of generating type gear cutting equipment in the production of bevel gears.

"Bevel gears too large to be cut...<snip>...

"Although generating methods are to be preferred, there are still some cases where
straight bevel gears are produced by milling. Milled gears cannot be produced with
the accuracy of generated gears and generally are not suitable for use in high-speed
applications or where angular motion must be transmitted with a high degree of
accuracy. Milled gears are used chiefly as replacement gears in certain applications,
and gears which are subsequently to be finished on generating type equipment are
sometimes roughed out by milling...

And having made bevel gears on a milling machine, I can attest to the truth of
this statement. They work like crap! Very rough turning.

-Chuck Harris

lothar baier wrote:
First off the 8640B was designed in spokane and as to my knowledge this division was disolved years ago, most
engineers were send to other divisions or into early retirement. This question would have to be answered by a ME and
not a EE , most large companies have a strict separation in between system engineering, mechanical engineering and
electrical engineering, then the ME who designed the gear doesnt necesarily have knowledge about who makes the gear
this is normally done by purchasing. so even the ME might not have the info you are looking for. I doubt HP used
catalog parts, HP was famous for custom parts, yes the qty was not too high for the stanbarts of running a injection
molder but first of you dont have to think in today standarts but have to think 20 to 30 years back plus the 8640 was
not cheap so HP could afford to pay a premium on the price. A CNC with a CNC Dividing head could possibly do the
job, you would have to slant the dividing head, the other part could be hobbed.
                         

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Re: opertunity to have uWaveEngineer1968 test his gear hobber - 8640B for $1

#8977

lothar baier wrote:
still trying to figure out where you get the hour for hobbing the gear from !Does your machine set itself up as you change gear types?

As I said, one gear will take a couple of hours to make, there
is some economy of scale, but you are unlikely to want to cut
more than ten gears in a production run.

...

those are small parts with fairly large DP in soft material, according to some preliminary calculations based on
delrin and my machine handbook it should take about 10-15minutes to hob 1gear !
The biggest challenge in casting is to get airpockets out, one way is to use a cylinder to push the epoxy into the
form until the material overflows out of a second hole, or you can put the form on a vibrator to achieve this, im not
an expert but i have seen some castings done and thats how they did it.You use very thin epoxy casting compounds.  They flow very nicely.
Once they are in the mold, you hit the vacuum, and draw the bubbles
out for a perfect fill.

-Chuck Harris

Re: opertunity to have uWaveEngineer1968 test his gear hobber - 8640B for $1

lothar baier

#8976

i remember years and years ago we had a similar problem with another plastic part, we used a part sprayed graphite on it and then plated over a layer of copper, this served as a EDM tool, problem was we had to make 3 of them because they wore out.
  most EDMs i looked at have 3 parts, the machine itself, a power supply and a pump that circulates and filters the dielectric fluid, i havent seen a machine with a 50W supply, even the smallest ones are in the KW range, dont know why they use 3 phase , im not the guy who designed the machine, my guess is that it is better in large shops where you have numerous machines to distribute the load , i dont know !
  check ebay under hansvedt, there is stuff out there, i have a 19x19ft two story shop, right now filled with the gear hobber, a large floor drill press, lathe, grinder and some work benches, what i really desire right now is a mill and a surface grinder   
     
Chuck Harris <cfharris@...> wrote:
          Hi Lothar,

The electrode could be something as fancy as a CNC made
graphite model, or it could be something as simple as
adding a little plating to the original plastic gear.

There is no intrinsic reason that an EDM machine should
need 3 phase power, the power requirements for one that
could handle a part this size are very modest... well under
50 watts.

I generate my own 3 phase in my shop. It is easy to do,
and all you need is a big 3 phase motor, and some simple
control components to get it started.

As John said, a silicone mold of the original gear would
be the easiest way.... Damn!.. I wanted an EDM machine.

-Chuck Harris

lothar baier wrote:
i was eyeballing a EDM for a bit but unfortunatly dont have enough floorspace right now, another problem is that most
EDMs require 3phase current which i dont have out here. There are some benchtop type hansved edms on ebay every once
in a while. Another issue it that you need to have a electrode that resembles the form of the gear made of graphite
or copper and usually those are CNC machined parts

                         

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Re: opertunity to have uWaveEngineer1968 test his gear hobber - 8640B for $1

#8975

You can't do a decent job of cutting a bevel gear on a mill.  To quote
Machinery's Handbook:

"Cutting Bevel Gear Teeth - A correctly formed bevel gear tooth has the same
sectional shape throughout its length, but on a uniformly diminishing scale from the
large to the small end.  The only way to obtain this correct form is by using a gener-
ating type of bevel gear cutting machine.  This accounts, in part, for the extensive use
of generating type gear cutting equipment in the production of bevel gears.

"Bevel gears too large to be cut...<snip>...

"Although generating methods are to be preferred, there are still some cases where
straight bevel gears are produced by milling.  Milled gears cannot be produced with
the accuracy of generated gears and generally are not suitable for use in high-speed
applications or where angular motion must be transmitted with a high degree of
accuracy.  Milled gears are used chiefly as replacement gears in certain applications,
and gears which are subsequently to be finished on generating type equipment are
sometimes roughed out by milling...

And having made bevel gears on a milling machine, I can attest to the truth of
this statement.   They work like crap!  Very rough turning.

-Chuck Harris



lothar baier wrote:

Show quoted text

First off the 8640B was designed in spokane and as to my knowledge this division was disolved years ago, most
engineers were send to other divisions or into early retirement. This question would have to be answered by a ME and
not a EE , most large companies have a strict separation in between system engineering, mechanical engineering and
electrical engineering, then the ME who designed the gear doesnt necesarily have knowledge about who makes the gear
this is normally done by purchasing. so even the ME might not have the info you are looking for. I doubt HP used
catalog parts, HP was famous for custom parts, yes the qty was not too high for the stanbarts of running a injection
molder but first of you dont have to think in today standarts but have to think 20 to 30 years back plus the 8640 was
not cheap so HP could afford to pay a premium on the price. A  CNC with a CNC Dividing head could possibly do the
job, you would have to slant the dividing head, the other part could be hobbed.

Re: opertunity to have uWaveEngineer1968 test his gear hobber - 8640B for $1

#8974

Show quoted text

----- Original Message ----- 
From: "John Miles" <jmiles@...>
To: <hp_agilent_equipment@...>
Sent: Thursday, November 08, 2007 1:57 PM
Subject: RE: [hp_agilent_equipment] Re: opertunity to have uWaveEngineer1968 test his gear hobber - 8640B for $1

I'm sure that if someone actually does the work and offers a full set of
good-quality 8640 gears for $50 or less, the customers will be there.  At
least one, anyway!  (raises hand)  At $100 or more you are competing with
parts-mule prices, so it doesn't make as much sense to create new gears if
that's what it would cost.This is precisely the problem with Chuck's proposal.  If one *has* the
parts mule generator, then one has the gears needed.  Natural priority
is to repair your generator first and worry about finding the off-the-shelf
equavilents later.

Best Regards,

Bob Groschen
Monument, CO

Re: 419A Chopper Replacement

#8973

they  can  be  replaced  with  zener  diodes  and  bypass  caps

Show quoted text

----- Original Message ----- 
  From: Christian A Weagle 
  To: hp_agilent_equipment@... 
  Sent: Thursday, November 08, 2007 9:20 PM
  Subject: [hp_agilent_equipment] Re: 419A Chopper Replacement

  Well, here I am answering my own question(s). This one was sort of my
  fault. To wit:

  When I got this unit, I tried to turn it on, no luck. Seeing the
  battery charge pushbuttons, I feared the worst (leaky cells corroding
  the PCBs), and opened it up. Found some wacky NiCds (basically, four
  'cells', each the size of sub-Cs, each labelled as 6V 225mAh (so
  probably 5 big fat coil cells in fancy wrapping), chained up to
  provide +/- 12V, and dated in the early 80's) that were truly dead -
  no leaks though. I removed them as some stickers on the back of the
  unit implied that they were trickle charged whenever it was plugged
  in, and they probably wouldn't like that in their current state!

  Changed a bunch of the electrolytic caps too. I then proceeded to
  operate the unit, sort of. It was all drifty, lots of random brief
  full-scale deflections, couldn't cal the photochopper, etc... Changed
  the rest of the caps. No help.

  After a close perusal of the power supply page of the schematic,
  though, I saw what was wrong. The only place that this meter gets
  its' internal ground is from the center of that battery stack! It
  basically runs from, and continuously charges them from, the top and
  bottom of a full-bridge rectifier. Ground is sort of virtual - if
  there are no batteries, there is no fixed ground. Hacking in a pair
  of 12-cell NiMH packs makes everything better - no drifts or abrupt
  swings, and I could cal the photochopper.

  The packs are somewhat higher voltage, but I think they should
  regulate down to the correct 12V after a while of running off them to
  discharge them, before plugging the unit in.

  What an unusual way of doing business!

Re: 419A Chopper Replacement

#8972

Well, here I am answering my own question(s).  This one was sort of my
fault.  To wit:

When I got this unit, I tried to turn it on, no luck.  Seeing the
battery charge pushbuttons, I feared the worst (leaky cells corroding
the PCBs), and opened it up.  Found some wacky NiCds (basically, four
'cells', each the size of sub-Cs, each labelled as 6V 225mAh (so
probably 5 big fat coil cells in fancy wrapping), chained up to
provide +/- 12V, and dated in the early 80's) that were truly dead -
no leaks though.  I removed them as some stickers on the back of the
unit implied that they were trickle charged whenever it was plugged
in, and they probably wouldn't like that in their current state!

Changed a bunch of the electrolytic caps too.  I then proceeded to
operate the unit, sort of.  It was all drifty, lots of random brief
full-scale deflections, couldn't cal the photochopper, etc...  Changed
the rest of the caps.  No help.

After a close perusal of the power supply page of the schematic,
though, I saw what was wrong.  The only place that this meter gets
its' internal ground is from the center of that battery stack!  It
basically runs from, and continuously charges them from, the top and
bottom of a full-bridge rectifier.  Ground is sort of virtual - if
there are no batteries, there is no fixed ground.  Hacking in a pair
of 12-cell NiMH packs makes everything better - no drifts or abrupt
swings, and I could cal the photochopper.

The packs are somewhat higher voltage, but I think they should
regulate down to the correct 12V after a while of running off them to
discharge them, before plugging the unit in.

What an unusual way of doing business!

Re: opertunity to have uWaveEngineer1968 test his gear hobber - 8640B for $1

#8971

arthurok wrote:
i  think  a   cnc machine  could  do  the job  Of course it could, but it would take some specialized
cutters to cut the gear teeth.  These cutters are
extremely expensive, on the order of $80 each.

Any machine shop would charge you close to 1000 dollars
just in setup and tooling charges.

Those setup and tooling charges are why I brought all
my machining back in-house.  In my prototype work, I do
a lot of one-off jobs, and the outside shop charges were
killing me.

-Chuck Harris

Re: opertunity to have uWaveEngineer1968 test his gear hobber - 8640B for $1

#8970

Hi Lothar,

The electrode could be something as fancy as a CNC made
graphite model, or it could be something as simple as
adding a little plating to the original plastic gear.

There is no intrinsic reason that an EDM machine should
need 3 phase power, the power requirements for one that
could handle a part this size are very modest... well under
50 watts.

I generate my own 3 phase in my shop.  It is easy to do,
and all you need is a big 3 phase motor, and some simple
control components to get it started.

As John said, a silicone mold of the original gear would
be the easiest way.... Damn!.. I wanted an EDM machine.

-Chuck Harris

lothar baier wrote:

Show quoted text

i was eyeballing a EDM for a bit but unfortunatly dont have enough floorspace right now, another problem is that most
EDMs require 3phase current which i dont have out here. There are some benchtop type hansved edms on ebay every once
in a while. Another issue it that you need to have a electrode that resembles the form of the gear made of graphite
or copper and usually those are CNC machined parts

54120A/B interface cable tip

#8969

Hello everybody:
It seems that the interface cable for a 54120A/B system is very simple
to clone. All connections are straight thru and it can be built in
about an hour.
You can get all the parts from digikey

MB50H-ND is the flat shielded cable (5 feet)
MDB50K-ND (two) are the connectors (50 pins Delta connector)
MDBF50-ND (two) are the backshells...plastic no metal version
MDSF50-ND (two) are the strain relief brackets.

Some extra copper tape to shield the connectors and it is ready to
play.
Cheaper (about $92 with shipping) than paying the $160 from a dealer.

Re: opertunity to have uWaveEngineer1968 test his gear hobber - 8640B for $1

lothar baier

#8968

still trying to figure out where you get the hour for hobbing the gear from !
  those are small parts with fairly large DP in soft material, according to some preliminary calculations based on delrin and my machine handbook it should take about 10-15minutes to hob 1gear !
   
  The biggest challenge in casting is to get airpockets out, one way is to use a cylinder to push the epoxy into the form until the material overflows out of a second hole, or you can put the form on a vibrator to achieve this, im not an expert but i have seen some castings done and thats how they did it.  

Chuck Harris <cfharris@...> wrote:
          lothar baier wrote:
Some things or actually a lot of things we do for a hobby have nothing to do with logic, sometimes you just do things
for fun, i have about $350 in the hobber including all acessories, i bought it not to make money but i figured that
its a nice complement to my metal hobby shop and $350 is a ammount that i can justify spending on a hobby !I wouldn't argue against that, I have tens of thousands of dollars
in my machine shop. But I still won't waste my time hobbing a
gear that I can buy for $2. I would rather spend my shop time on
things that would be too expensive to purchase, if I could buy
them at all.

Why would
somebody want to fix testequipment or build a ham radio rig ? it cheaper to buy especially if you put in all the time
you spend - you do it for fun and to learn something, you gain alot of valuable skills by practicing - as it says
practice makes perfect, the other reason is that you have control over your parts and even if they are not available
anymore down the road you can still make them and fix your equipment, also you can make them better by using more
advanced materials. Plastic gears normally are not hobbed except if you use delrin, You are in luck, the HP gears are already delrin on brass hubs.

Like nylon, delrin shrinks continually. Unfortunately, the brass hubs do not, so
given time, the gear will break at one of its roots.

PVC is a pain because it leaves a

I am not sure what PVC has to do with anything proposed.

bunch of burrs that need to be removed, the other side of PVC is that it becomes brittle over the years, normally the
gears HP used were made in a very crude way - injection molding which has a high yield and is cheaper in Qty. My idea
is to either use delrin or aluminum, the forces on the flanks of those gears are not very high and the rotating speed
is very slow so by far the specs are no challenge. All you need to know to make them is the number of teeth , the
diameter and the pressure angle, height and id of the gear.And that information is what I was going to provide to the group.

If you hobb the gears, and make them available for sale, you
will quickly discover that you have to charge something for your
time, tooling and materials. Suddenly, you will see why metal
gears are so damned expensive... custom gears even more so.

If you are using manually operated machines (at $350, I think you are),
between blanking the gears, and hobbing the teeth, you will have several
hours in each gear you make.

US microwave engineers with experience are making what these days? $90K
to $130K? That works out to $40 to $60/hour paid to the engineer. They
cost their companies 2 to 3 times that much.

I don't think the guys that hang out on this group are going to be willing
to pay you $200 per gear. If you charge $5 per gear, your wife will divorce
you. I offered several gear *sets* at the cost of one broken 8640B OPT/1/2/3.

My price exceeded what the market would bear... even though I would essentially
be working for free.

-Chuck Harris


                         

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Re: opertunity to have uWaveEngineer1968 test his gear hobber - 8640B for $1

lothar baier

#8967

still trying to figure out where you get the hour for hobbing the gear from !
  those are small parts with fairly large DP in soft material, according to some preliminary calculations based on delrin and my machine handbook it should take about 10-15minutes to hob 1gear !
   
  The biggest challenge in casting is to get airpockets out, one way is to use a cylinder to push the epoxy into the form until the material overflows out of a second hole, or you can put the form on a vibrator to achieve this, im not an expert but i have seen some castings done and thats how they did it.  

Chuck Harris <cfharris@...> wrote:
          lothar baier wrote:
Some things or actually a lot of things we do for a hobby have nothing to do with logic, sometimes you just do things
for fun, i have about $350 in the hobber including all acessories, i bought it not to make money but i figured that
its a nice complement to my metal hobby shop and $350 is a ammount that i can justify spending on a hobby !I wouldn't argue against that, I have tens of thousands of dollars
in my machine shop. But I still won't waste my time hobbing a
gear that I can buy for $2. I would rather spend my shop time on
things that would be too expensive to purchase, if I could buy
them at all.

Why would
somebody want to fix testequipment or build a ham radio rig ? it cheaper to buy especially if you put in all the time
you spend - you do it for fun and to learn something, you gain alot of valuable skills by practicing - as it says
practice makes perfect, the other reason is that you have control over your parts and even if they are not available
anymore down the road you can still make them and fix your equipment, also you can make them better by using more
advanced materials. Plastic gears normally are not hobbed except if you use delrin, You are in luck, the HP gears are already delrin on brass hubs.

Like nylon, delrin shrinks continually. Unfortunately, the brass hubs do not, so
given time, the gear will break at one of its roots.

PVC is a pain because it leaves a

I am not sure what PVC has to do with anything proposed.

bunch of burrs that need to be removed, the other side of PVC is that it becomes brittle over the years, normally the
gears HP used were made in a very crude way - injection molding which has a high yield and is cheaper in Qty. My idea
is to either use delrin or aluminum, the forces on the flanks of those gears are not very high and the rotating speed
is very slow so by far the specs are no challenge. All you need to know to make them is the number of teeth , the
diameter and the pressure angle, height and id of the gear.And that information is what I was going to provide to the group.

If you hobb the gears, and make them available for sale, you
will quickly discover that you have to charge something for your
time, tooling and materials. Suddenly, you will see why metal
gears are so damned expensive... custom gears even more so.

If you are using manually operated machines (at $350, I think you are),
between blanking the gears, and hobbing the teeth, you will have several
hours in each gear you make.

US microwave engineers with experience are making what these days? $90K
to $130K? That works out to $40 to $60/hour paid to the engineer. They
cost their companies 2 to 3 times that much.

I don't think the guys that hang out on this group are going to be willing
to pay you $200 per gear. If you charge $5 per gear, your wife will divorce
you. I offered several gear *sets* at the cost of one broken 8640B OPT/1/2/3.

My price exceeded what the market would bear... even though I would essentially
be working for free.

-Chuck Harris


                         

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