Shop Floor Talk  

Go Back   Shop Floor Talk > Welding and Metalworking Forums > Mechanical & Electrical

SFT Search:   
Reply
 
Thread Tools Display Modes
  #1  
Old 09-04-2020, 05:24 PM
Walker's Avatar
Walker Walker is offline
Standard of Excellence
 
Join Date: Aug 2004
Location: Cave Creek AZ
Posts: 4,671
Default Underhood rotary air compressor

I ran into a very nice VMAC air underhood 70cfm compressor that I decided I couldn’t live without. It is just the air end, none of the accessory parts. In order to install it I would need a bracket, oil/air separator with coalescing filter, oil cooler, and throttle control.

If I buy all the manufacturers parts new it is somewhere in the 4 grand neighborhood. None of the items frighten me to make them except for the electronic controls. The oil/air separator is marginally confusing as far as how it filters, returns, and scavenges oil, but a unit from any rotary screw compressor would likely work fine, though size and space to install would be a consideration.

The unit is originally set up with lots of electronic controls to raise engine speed, shut off engine when not using air, over temp shut off, cab air temp monitoring, etc. this unit makes enough air at idle for most of my needs, and with the addition of a storage tank would likely be cycled off more than on, so I am not sure that I would even require all the electronic gizmos.

Has anyone ever monkeyed around with these? Installed or operated? Can they be wired with a simple pressure switch through the clutch like an a/c system?

I have attached a picture I stole from the internet of the compressor.

Thanks
Attached Thumbnails
Click image for larger version

Name:	1A7A0539-3FAB-4B26-965F-B62139CAF727.jpeg
Views:	207
Size:	23.7 KB
ID:	157587  
__________________
Walker
Chief slag chipper and floor sweeper, Ironwood Artistic

Last edited by Walker; 09-05-2020 at 09:22 AM. Reason: Spelling
Reply With Quote
  #2  
Old 09-04-2020, 07:22 PM
Whitetrash's Avatar
Whitetrash Whitetrash is offline
Elite Member
 
Join Date: Mar 2009
Location: Estes Park, CO [Around 8000 Ft. Elv.]
Posts: 4,357
Default

I think it can be done in a even more simple fashion. Rotary compressors aren't really meant to be cycled in and out. They are either on or off. Wire the clutch with a main power switch and employ a pop-off valve to vent excess air while you are using it. Just for safety's sake I would use a tee fitting with 2 pop-offs with slightly different cracking pressures to guarantee system safety.
__________________
"Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery."
Winston Churchill
Reply With Quote
  #3  
Old 09-04-2020, 08:35 PM
Norm W's Avatar
Norm W Norm W is offline
Elite Member
 
Join Date: May 2006
Location: Syracuse, NY
Posts: 3,028
Default

Sounds like a spot for an unloader valve.
__________________
Make over, make do, or do without

Why do I have to press one for English when you're just gonna transfer me to someone I can't understand anyway?

Grant me the strength to accept the things I cannot change, the courage to change the things I can & the friends to post my bail when I finally snap!
Reply With Quote
  #4  
Old 09-04-2020, 10:03 PM
Whitetrash's Avatar
Whitetrash Whitetrash is offline
Elite Member
 
Join Date: Mar 2009
Location: Estes Park, CO [Around 8000 Ft. Elv.]
Posts: 4,357
Default

Quote:
Originally Posted by Norm W View Post
Sounds like a spot for an unloader valve.
A D-2 governor for an air brake system would probably work awesome it would keep system pressure 125 Lbs. Max. All truck air brake compressors run all day long and the D-2 cycles them in and out. They are all old school piston compressors with fairly low CFM. I really think a high capacity rotary will work way better with a K.I.S.S. Pop-off system. Let it run at it's most efficient RPM/ workload and just piss off excess air.
__________________
"Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery."
Winston Churchill
Reply With Quote
  #5  
Old 09-05-2020, 09:20 AM
Walker's Avatar
Walker Walker is offline
Standard of Excellence
 
Join Date: Aug 2004
Location: Cave Creek AZ
Posts: 4,671
Default

Good ideas. I found a regular compressor unloaded that had the cam capacity, haven’t found the capacity of the D-2. Most of the pop offs I have dealt with (mostly Fisher natural gas service) are fairly crude and loud.
__________________
Walker
Chief slag chipper and floor sweeper, Ironwood Artistic
Reply With Quote
  #6  
Old 09-05-2020, 09:56 AM
Ironman's Avatar
Ironman Ironman is offline
Iron Modification Investigator
 
Join Date: Feb 2008
Location: Warburg, Alberta, Canada
Posts: 16,787
Default

Quote:
Originally Posted by Walker View Post
Good ideas. I found a regular compressor unloaded that had the cam capacity, haven’t found the capacity of the D-2. Most of the pop offs I have dealt with (mostly Fisher natural gas service) are fairly crude and loud.
They are loud. Sound like a kid with a fart can muffler on his Honda.
A D2 governor is a good idea, and the compressor can be 1200 cfm or 2cfm. All it does is shunt air from tank pressure to lift the intake valves at the pressure set for.

All rotary compressors I have used have a butterfly on the intake to control the air volume pumped. A large throttle plate from a vehicle can be mounted and a little air cylinder controlled by the D2 will open and close it as needed.

Of more concern is the oil separator. I would buy a separator screen, and go look at a VMAC unit and copy the case that the separator sits in.

Also you need to look at the oil injection metering from the reservoir tank to the compressor intake.
__________________
Gerry
You got freedom of speech, if you don't say too much.
Aaron Neville.

When a liberal screams racism, you can bet they were also born with white skin.

The countries whom the gods would destroy they first make green. Rex Murphy
Reply With Quote
  #7  
Old 09-09-2020, 09:11 PM
Walker's Avatar
Walker Walker is offline
Standard of Excellence
 
Join Date: Aug 2004
Location: Cave Creek AZ
Posts: 4,671
Default

The compressor arrived today. All outlets were capped off. The outside castings looked great, no tool or rub marks. I pulled off the intake header and the screws are spotless, not a scuff, or minor imperfection.

The intake valve looks to be opened with vacuum (spring to close when off), then closed with air pressure. There is some sort of spring balance and screw to adjust.
There is an oil feed coming from the separator tank that apparently uses tank pressure to blow the oil back, through a filter to the intake at the compressor pump. There is an oil drain line that takes the oil that runs to the bottom of the screw cavity back to the separator tank. This runs at head pressure, so slightly more than tank pressure. Then there is the high pressure air/oil line to the separator tank.

Aside from the clutch and a pressure transducer, I see no reason it couldn't be run without the thousand dollar electronics package, as there are no electric controls on the pump.

The separator tank with the blow down valve should be here early next week.

I did put in for a quote for the install parts, including the electronics package. After I see that I will know if I am making my own bracket and controls or buying them.

I did get a good look at my accessory drive set up. There is a large cast aluminum bracket that the PS pump and alternator mounts to. If I remove that and do a minor but of machine work (could be done with a sander if needs be) I could make a bracket. Likely take about 5 hours to uninstall, construct and reinstall.Click image for larger version

Name:	KIMG0459.jpg
Views:	166
Size:	196.2 KB
ID:	157625

Sent from my E6810 using ShopFloorTalk mobile app
__________________
Walker
Chief slag chipper and floor sweeper, Ironwood Artistic
Reply With Quote
  #8  
Old 09-11-2020, 05:04 PM
Whitetrash's Avatar
Whitetrash Whitetrash is offline
Elite Member
 
Join Date: Mar 2009
Location: Estes Park, CO [Around 8000 Ft. Elv.]
Posts: 4,357
Default

You said you were going to need a oil cooler. That jogged the memory banks. A friend of ours had a Speed Shop with her husband before he passed from cancer. She brought up a load of stuff for me to try to sell which is rat-holed in the shed somewhere. I know there are at least a couple coolers made by Earl's I found pics of 2 NOS still in the box. If you are interested I will do a search to find them. I actually think there are more maybe 4 total of various sizes
Attached Thumbnails
Click image for larger version

Name:	DSCF0017.jpg
Views:	154
Size:	200.4 KB
ID:	157631   Click image for larger version

Name:	DSCF0018.jpg
Views:	152
Size:	197.0 KB
ID:	157632  
__________________
"Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery."
Winston Churchill
Reply With Quote
  #9  
Old 09-11-2020, 09:55 PM
Walker's Avatar
Walker Walker is offline
Standard of Excellence
 
Join Date: Aug 2004
Location: Cave Creek AZ
Posts: 4,671
Default

The oil cooler I am seeing as typical for this are the brazed plate coolers that have coolant running through them. Why the difference I don’t really know, could be the pressure, as the oil would be at 175 psi. With that pressure I would think a little nick in the aluminum would be the death knell for it, and messy too.
__________________
Walker
Chief slag chipper and floor sweeper, Ironwood Artistic
Reply With Quote
  #10  
Old 09-12-2020, 08:41 AM
Whitetrash's Avatar
Whitetrash Whitetrash is offline
Elite Member
 
Join Date: Mar 2009
Location: Estes Park, CO [Around 8000 Ft. Elv.]
Posts: 4,357
Default

Ah, OK I did not realize they would be operating at that high a pressure. You are correct these wouldn't cut it for that.
__________________
"Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery."
Winston Churchill
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Web Search:

All times are GMT -5. The time now is 07:19 AM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2023, vBulletin Solutions Inc.