From my experiences, 15 rpm is extremely fast, see with the same thickness you will usually weld stuff on the positioner, say 3 inch diameter weld about 9 inches and check how long does it takes.

The other thing i hate on mine is the slightest backlash on the gear reducer combined with the drag from ground on the part/shaft/whatever is really annoying.

I do not use mine very often, there are some mechanical flaws to correct and my operator skills are also questionable. the first motor i used was a 12 volts wiper motor, replaced that with a 24 volts wire feeder motor from an old mig. If i remember well most of the time i was in the .3 to 2.00 rpm but that just me

 

Thanks. I have no experience with a positioner, just going by the specs for other units so your info was really helpful.

Jody has a video where he mentions 1/8" per second on the circumference is about ideal for welding. Given that, your 3in pipe example = 75sec to weld, so that is ~0.8rpm.

Running some quick numbers:
1/2" tube = 5rpm
2" tube = 0.8rpm
8" pipe = 0.3rpm

That means the deeper I can gear it the better. I was thinking 180:1 final ratio, so that gives me a max of ~9rpm, but if I geared it at 240:1 max would be max of 6rpm which is just about the max I would ever need. I am not really worried about the low end since I should be able to run the drill down pretty slow in low gear. How low remains to be seen.

 

As I read through the posts, I was thinking that 15rpm was way too fast as well. Good to see you have some ideas on how to slow it down further. Yes, the motor could be slowed, but motors don't really like running continually at slow speeds. At least, my hand drills never seem to last with the trigger only pulled in 1/4 way!!

However, any chance you would want the ability to spin it faster for re-positioning or finishing(grinding/sanding) jobs? Perhaps having some way (transmission??) to change speed ranges would be a good idea??

Andrew

 

Now I'm wondering if I don't want to gear it even lower with a second speed reducer instead of sprockets. My plan was to use the 60:1 with a 3 or 4:1 sprocket drive, but based on the comments it might be better to gear it to max out at 3 or 4 rpm with the drill motor running at 50-75%. A second speed reducer would blow my budget straight out of the water though....

 

hjs552, coupling 2 speed reducers could double the backlash yours already have.... Ideally it has to be zero otherwise when the ground is transmitted to the rotating motion it may produce, some vibrations or hesitations 'jerking' ...it does on mine, i have carbon brushes right under the lathe chuck on the steel shaft. to reduce from motor to the reducer i used a 3/8 timing belt and pulleys to meet my expectations. It's about 25% fail so far...workable but sometimes irritating.

 

Hmm. That is a good point. In light of that I think I will just use the one speed reducer for now and if I cant get the rpms in the right range I will try and fix it with another form of gearing.

I am considering making some form of CVT pulley system sort of like they use on gocart torque converters. That would give a variable ratio from 5:1 to 1:5 if it works.

Sent from my S4 using Tapatalk

 

Could you use a potentiometer in the switch so you can control the speed very precisely?

 

Not sure how well that would work. It might be difficult to control two variable foot pedals at the same time. On the other hand it might work pretty good.

I think i am going to stick with a on/off pedal for now.

Sent from my S4 using Tapatalk

 

My Aircrafter positioner only goes to 2 RPM wide open.

15 RPM is impossible to work with.



...zap!

 

Thanks zapster. Its decided now - max will be closer to 2 or 3 rpm. Don't know what I was thinking with the 15rpm. Now I've got to find a new motor setup.

 

Since you already have the Winsmith reducer, look out for a gearmotor with a 3/4" shaft. If you can find a DC or 3-phase gearmotor you can run it with a commercial speed control. All of the above are pretty easy to find on Fleabay, etc.

John

 

I will second what Zap says. I have a MBC positioner and I got the 0-18 rpm model. After playing with it a bit on 2 and 3 inch tubing I am lucky if I break 1-1.5 rpm. All the rest for me are not needed.

Sent from my SM-T715Y using Tapatalk

 

I took a look at one of the positioners at work and they are using a 90v Baldor motor and Minarik motor controller. It also has additional gearing with a chain drive around the chuck. The motor tops out at 30 rpm, and the secondary chain drive looks like 5:1 so this one tops out at around 6rpm if I had to guess.

I am still trying to decide on how to achieve similar gearing without spending $400 on components similar to the ones above.

 

I used a 12 volt winch motor and 12 volt power supply and a pulse width Modulator for a Bead Roller variable speed drive. I am going to use a similar setup for a weld positioner.:jester:
winch
http://www.ebay.com/itm/2000lb-Winc...Towing-Tool-/201511296444?hash=item2eeb025dbc:m:mIrEMRRyAu5rDt6YnLmXBfA&vxp=mtr

power supply
http://www.ebay.com/itm/12V-DC-20A-...-for-LED-Strip-Light-Metal-/131474555017?hash=item1e9c7e8089:g:-PcAAOSwBLlVSTl3

PWM 12 volt
http://www.ebay.com/itm/PWM-Convert...r-Controller-Switch-/190898607519?hash=item2c7271959f:m:mDE0-hfwS49g8kmgPyz-XRg

 

You will still some sort of reduction in the drive system. To get it to run has slow and steady has you would want. Something you might look at is using timing belt for your gear reducer like the use for CNC mills on stepper motors.