Official Luthiers Forum!
http://luthiersforum.com/forum/

Driving the .......bus
http://luthiersforum.com/forum/viewtopic.php?f=10101&t=49232		 Page 1 of 3
Author:  Clinchriver [ Mon Apr 10, 2017 6:32 am ]
Post subject:  Driving the .......bus
Looking at gear reducing motors for a radius dish sanding station. What rpm is optimum and minimum torque? I was thinking 10 to 20 rpm, and for minimum torque 200 inch pounds?
Author:  SteveSmith [ Mon Apr 10, 2017 6:51 am ]
Post subject:  Re: Driving the .......bus
I'm thinking 30ish rpm might be about right but I'm just guessing. Be nice to have a variable speed motor. Maybe find and old treadmill?

Sent from my SM-G930V using Tapatalk
Author:  Barry Daniels [ Mon Apr 10, 2017 9:16 am ]
Post subject:  Re: Driving the .......bus
Mine turns at about 120 rpm and that is a fairly comfortable pace. At 10 to 20 rpm you will be sanding for a long time.
Author:  SteveSmith [ Mon Apr 10, 2017 9:30 am ]
Post subject:  Re: Driving the .......bus
Greg, since I don't have room for a separate radius sanding station I've been thinking that I might be able to set up my downdraft table so I could have something removable on it to motorize my radius dish. Looking forward to seeing what kind of motor you come up with and then maybe I can figure out something.

Barry, glad to hear a higher rpm will work - anything that speeds up that process is good, in my opinion.
Author:  Clinchriver [ Mon Apr 10, 2017 10:15 am ]
Post subject:  Re: Driving the .......bus
Barry Daniels wrote:
Mine turns at about 120 rpm and that is a fairly comfortable pace. At 10 to 20 rpm you will be sanding for a long time.


Let's see and hear the particulars?
Author:  Clay S. [ Mon Apr 10, 2017 1:17 pm ]
Post subject:  Re: Driving the .......bus
"since I don't have room for a separate radius sanding station I've been thinking that I might be able to set up my downdraft table so I could have something removable on it to motorize my radius dish."

Some people run the motor against the edge of the radius dish. This can give you a favorable speed reduction without using pulleys or gears. Using a 30 inch dish and a 2 inch rubber bushing on the motor spindle could give a speed of 100 to 120 rpm for a 1725rpm motor. If you made a mount for the motor that would allow it to drop into the downdraft table and mounted the dish beside it you might even get some dust collection to go along with it.
Or you could sneak the wife's food processor out of the house occasionally......
Author:  SteveSmith [ Mon Apr 10, 2017 1:32 pm ]
Post subject:  Re: Driving the .......bus
Clay, you make a good point. If I drive the edge of the dish I could just use a standard motor. I might be able to build a skeleton frame to sit over the downdraft table when needed and not interfere with it's normal function ... hmmmmmmmmmm. I think I'll look at motors.
Author:  Pmaj7 [ Mon Apr 10, 2017 1:47 pm ]
Post subject:  Re: Driving the .......bus
My bus driver is on strike until some bit of automation is in place. Probably going to do some sort of side drive. There have been some pretty good threads. Worth a search.
Author:  klooker [ Mon Apr 10, 2017 1:57 pm ]
Post subject:  Re: Driving the .......bus
One thing you may want to look at is using a VFD (variable frequency drive, aka AC Drive) and a 3-phase motor. VFD's give you variable speed control of a 3-phase motor along with other cool features like soft starting & braking. You can usually find 3-phase motors much cheaper than single phase motors and they are a lot simpler, meaning there is a lot less that can go wrong with one.

This unit is nice because it allows you to run up to a 1HP motor with regular 115V household electricity.
Attachment:
FM50-101-C_main-1.jpg

http://www.factorymation.com/FM50-101-C

That company has also been very helpful with tech support when you go to set up the unit. I put one on a drill press with a potentiometer that allows me to to control the speed.

Kevin Looker
Author:  Bryan Bear [ Mon Apr 10, 2017 2:13 pm ]
Post subject:  Re: Driving the .......bus
SteveSmith wrote:
Clay, you make a good point. If I drive the edge of the dish I could just use a standard motor. I might be able to build a skeleton frame to sit over the downdraft table when needed and not interfere with it's normal function ... hmmmmmmmmmm. I think I'll look at motors.


Sounds like it is time to look for a good deal on a Craigslist bench-top drill press. You could probably get one cheaper than buying a motor and it would be intended for vertical positioning. I have thought of doing this off and on but never pulled the trigger. Just be sure you don't have a spinable dish when you are using it for go bar clamping. eek
Author:  SteveSmith [ Mon Apr 10, 2017 2:19 pm ]
Post subject:  Re: Driving the .......bus
Bryan Bear wrote:
SteveSmith wrote:
Clay, you make a good point. If I drive the edge of the dish I could just use a standard motor. I might be able to build a skeleton frame to sit over the downdraft table when needed and not interfere with it's normal function ... hmmmmmmmmmm. I think I'll look at motors.


Sounds like it is time to look for a good deal on a Craigslist bench-top drill press. You could probably get one cheaper than buying a motor and it would be intended for vertical positioning. I have thought of doing this off and on but never pulled the trigger. Just be sure you don't have a spinable dish when you are using it for go bar clamping. eek


Good point laughing6-hehe
Author:  bluescreek [ Mon Apr 10, 2017 2:46 pm ]
Post subject:  Re: Driving the .......bus
look for an old potters wheel
perfect tool for running the bus
Author:  Barry Daniels [ Mon Apr 10, 2017 3:08 pm ]
Post subject:  Re: Driving the .......bus
OK, here are details of my setup. I made a turn-table with a large plastic lazy susan bearing from Grainger. It is turned with a long fan belt by a 1/3 hp, 1140 rpm motor mounted under my workbench. The motor's shaft sticks up through the bench top with a 2" diameter pulley. The lazy susan has a fan belt shape that was routed into the edge and it is 24" in diameter. If someone wants to run the numbers you could determine the platen rpm. The first photo shows how the turn-table mounts to the front of my work bench. The two wooden knobs engage threaded inserts in the bottom of the work bench top and they slide sideways in slots which allow the belt to be tightened up. Ignore the pipe mounts. Those are for my guitar clamping setup.
Author:  Barry Daniels [ Thu Apr 13, 2017 10:36 am ]
Post subject:  Re: Driving the .......bus
I found an online belt speed calculator and it came up with 95 rpm for my rig. I think that is a good compromise between speed and control.
Author:  Mike OMelia [ Sun Apr 16, 2017 12:48 pm ]
Post subject:  Re: Driving the .......bus
Of all the tasks involved, rim sanding is the most annoying. I have gotten tennis elbo from doing it. I'd love to be able to do it this way
Author:  doncaparker [ Sun Apr 16, 2017 2:33 pm ]
Post subject:  Re: Driving the .......bus
The open belt on Barry's setup scares me a bit.

I have been happy with both the torque and reduced speed I got from simply buying a cheap belt/disk sander from Harbor Freight ($65 or so), harvesting the 1750 rpm motor, attached pulley and belt, and slowing the speed down by using pulleys and belts to cut the rpm via ratios.

From the 1750 rpm motor and small pulley, have that belt drive a large pulley mounted on a shaft. On that same shaft, mount another small pulley. Have that small pulley drive a large pulley on the drive shaft. I can't give you exact numbers, because I don't know what motor, pulleys, belts, shafts and bearings you have access to. However, this is how you get the speed down to the range you want. The ratio between pulley sizes cuts the rpm by that ratio. Having a 2" pulley drive an 8" pulley cuts the rpm to 25% what it was before. When you do that twice, you can easily get down into the 100 rpm range. You just need to pick the right pulleys. Mine goes about 80 rpm, I think.
Author:  Barry Daniels [ Mon Apr 17, 2017 12:29 pm ]
Post subject:  Re: Driving the .......bus
The open belt doesn't seem to scare me at all and I am fairly safety conscious. The speed is low enough and the belt tension is loose enough that getting something in the belt has not been a problem so far. I am careful to keep loose clothing and my fingers away from the pinch points.
Author:  Mike OMelia [ Mon Apr 17, 2017 8:48 pm ]
Post subject:  Re: Driving the .......bus
Do any of you use center post bearings? And what about the bottom of the disk? What's it riding/sliding on? Finally, what kind of time and effort savings do u experience?
Author:  doncaparker [ Mon Apr 17, 2017 10:11 pm ]
Post subject:  Re: Driving the .......bus
I like the pulley reduction system I described above. I currently support the dish with a lazy susan and drive it with an extra pulley with bolts threaded into it. I really want to revamp my support and drive system to be like what is described in this thread:

viewtopic.php?f=10101&t=48649&hilit=dish+sander

Time and effort savings? It's pretty dramatic how big a difference it makes. I'm never driving the bus again; I'm spoiled.
Author:  Hesh [ Tue Apr 18, 2017 5:00 am ]
Post subject:  Re: Driving the .......bus
Forgive me please as I did not read any of the posts in this thread before posting. But.... I wanted to share a revelation that I once had that helped me out. It was so very stupid too that I am almost embarrassed to mention it.

I once wanted to motorize my radius dishes back when I was producing more than one guitar a month.... Driving the bus sucked.... and aggravated my hernias.

Then one morning it occurred to me that if I profile the radius of the rim with the dish BEFORE.... installing the kerfed linings..... and was careful to then glue and clamp my linings around 1/32nd" proud of the profiled rim only minimal bus driving was required. Reason being I was just kissing the linings in the dish and since they are way thicker than the sides this reduced my dish time, bus driving time by about 2/3rds...... Don't ya love fractions....;)

I'm sure many of you either knew this or already do this but for those of us who didn't and don't bus driving time can be significantly reduced and was for me.

;) Interestingly enough I suspect that those of us who this never occurred to, like me.... :? may not be willing to admit it here and that's OK. I'm happy to be today's forum idiot.... [headinwall] gaah laughing6-hehe :D if it helps just one other person, hopefully more.

Now we return to our regularly scheduled program..... but before we do perhaps the term needs to be updated to "sharing a Zipcar" or "using your app to summon an Uber..." Busses are so last century.
Author:  bcombs510 [ Tue Apr 18, 2017 5:47 am ]
Post subject:  Re: Driving the .......bus
That is the method that OBrien shows in his videos so I use it as well. I didn't realize there was another way. :)


Sent from my iPhone using Tapatalk
Author:  doncaparker [ Tue Apr 18, 2017 5:59 am ]
Post subject:  Re: Driving the .......bus
It is definitely important to follow Hesh's advice and profile the sides once before installing the linings. The thing that still makes even that task a bit of work is getting the blocks profiled right. So, the motorized dish is pretty handy all the way around.
Author:  kencierp [ Tue Apr 18, 2017 11:27 am ]
Post subject:  Re: Driving the .......bus
Totally agree about having the rim profiled so that only light sanding is needed to get the correct bevel of course we use our Mega Mold fixture for the complete operation -- no dishes involved. A cool feature of the MM is the ability to make/draw perfect side profile templates. Like the factories (Martin Taylor etc.) we profile before bending and use the inner waist curve apex as a locating point for the entire assembly process.

http://www.kennethmichaelguitars.com/si ... lates.html
Author:  Barry Daniels [ Tue Apr 18, 2017 3:24 pm ]
Post subject:  Re: Driving the .......bus
doncaparker wrote:
The open belt on Barry's setup scares me a bit.


I have given this some more thought and realize that it is a legitimate concern anytime you have belt driven tools. Since I use to work in the environmental field which was part of the safety department at NASA I feel the need to revisit this. It's not the open belt which is the hazard but what we call the "pinch points" which in this case is where the belt enters the two pulleys. The small, drive pulley is at the back of my workbench so the possibility for getting something ensnared is somewhat minimized. The second pinch point is at the back of my radius dish since it spins clockwise. The part that engages the belt here is protected by the larger radius dish which creates a shelf or partial cover for the pinch point. I really don't see any way to protect that further. I will however make a cover for the small drive pulley at the back of the workbench which should be relatively easy. Thanks for pointing out your concern.
Author:  doncaparker [ Tue Apr 18, 2017 4:03 pm ]
Post subject:  Re: Driving the .......bus
Barry--

Glad to hear you are taking precautions! I would not have nagged you too hard about it; I figure we all weigh risks every day, so you can decide your own balance of safety and utility. I just figured it was worth a mention, mostly for the sake of others.
Page 1 of 3 All times are UTC - 5 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/