Corvair DiagramCorvair Photo
Corvair Center
home forum corvairs calendar links Corvair Podcast
California Corvairs
Clarks Corvair
Clarks Corvair
“CORSA"



Chevy Corvair License Plate
Chevy Corvair Chrome Wheel
Corvair Center Forum :  Corvair Center Phorum The fastest message board... ever.
Corvair Center 
Current Page: 4 of 6
Re: Mechanical Fuel Pump Observations...
Posted by: krfjkm ()
Date: March 15, 2018 07:43PM

Looking forward to your results!

KRFJKM
Charlotte NC
1965 Corvair Corsa

Options: ReplyQuote
Re: Mechanical Fuel Pump Observations...
Posted by: JimBrandberg ()
Date: March 16, 2018 05:00AM

I got to wondering about oscillation when looking at various springs. Perhaps the spring design has more considerations than just pressure.
The spring companies seem to have three different materials; spring steel, stainless and music wire.
The only tapered spring in stock at a spring company I've found is too small in diameter, too short, 7.5 # spring rate instead of 10, 7 turns instead of 5 and music wire instead of spring steel. I got to thinking that some springs may fit but not control bounce or oscillation.

In trying to search spring company websites I'm finding that compression spring listings are easy to find, tapered or conical not so much. They show tapered springs in their pictures but most don't have a link to get into their tapered spring catalog or listing. I'd sure like to find a spring that's in stock somewhere but so far I can't, I'm not so good at Internet searching.

You're correct that 7/8 is pretty close to the installed height, maybe just a tad less. I have several long springs and would like to experiment with spring rates and weight changes when cutting and reforming if I can find the time.

Jim Brandberg
Isanti, MN
CorvairRepair.com

Options: ReplyQuote
Re: Mechanical Fuel Pump Observations...
Posted by: kenzen ()
Date: March 17, 2018 08:36AM

Jim,
I would think the stiffness of the diaphragm would have the biggest damping effect in the pump, and/but maybe preventing "float" (like with cylinder head valve/lifter behavior) may require the higher pressures. Maybe I can embed a sensor in the pump or on the push rod - need to think on that one. A position indicator and pressure transducer would give us dynamic data - I can use my cheap USB oscilloscope interface (2 channel) to pull data into my laptop. (This might be completely over-the-top for what we are trying to accomplish, but I used to do vibration analysis on electric motors with 3-axis accelerometers, and I'm a software engineer, so I'm in familiar territory here.)

I'm also understanding the highest quality steel is the "music wire" (negating corrosion resistance considerations). Might not matter for us. There's some interesting videos on YouTube of guys winding their own springs - if we can identify the right gauge wire and make a jig to put into a winding mechanism of some sort, this might be a "cottage industry" opportunity for small quantities of hand-wound springs. A bulk buy of wire (100'?) would make a lot of springs.

To measure the basic spring compression height, I was thinking of simply putting a blob of clay inside the spring so that it would compress in assembly, then just disassemble it and measure the clay compression height.

Another interesting observation is the factory drawings of the pump cross section do not have conical (or tapered) springs - they are regular compression springs. Maybe a regular (non-tapered) off the shelf spring would work?

I should have the NOS spring mid this week, along with the digital scale. Since I know the current Clark's spring I'm running is just a bit high in tension, I should have some good data by next weekend. I also just bought an ultrasonic sink to rebuild my carbs, so I'll be time-sharing between the tasks.

kenzen
66 Monza Coupe 110/PG
Bel Air, MD

Options: ReplyQuote
Re: Mechanical Fuel Pump Observations...
Posted by: JimBrandberg ()
Date: March 17, 2018 01:36PM

One thing about a tapered spring is that it compresses down into itself further before coil bind occurs. I'm not sure if that's an issue for us or not.

Jim Brandberg
Isanti, MN
CorvairRepair.com

Options: ReplyQuote
Re: Mechanical Fuel Pump Observations...
Posted by: jjohnsonjo ()
Date: March 17, 2018 02:30PM

I would say the taper has more to do with harmonics than bind.

J.O.

65 Corsa Turbo Vert
79 Honda XL 500S
69 Honda CL 160 D
2010 BMW F 650 GS
2003 Bounder 36D
2013 KIA Optima SX turbo-AKA ZIPPY (wife,s car)
69 Newport Holiday Sailboat
Baja 150 dune buggy cart
Coleman HS 500 UTV
2016 KIA Sorento SXL Turbo

Bethlehem,Pa

Image and video hosting by TinyPic

Options: ReplyQuote
Re: Mechanical Fuel Pump Observations...
Posted by: Wagon Master ()
Date: March 17, 2018 02:54PM

Keep in mind, we are talking about .147 of travel, correct?

Options: ReplyQuote
Re: Mechanical Fuel Pump Observations...
Posted by: kenzen ()
Date: March 17, 2018 03:22PM

Wagon Master Wrote:
-------------------------------------------------------
> Keep in mind, we are talking about .147 of travel,
> correct?


If it's tracking completely with the crank eccentric, yes. The tapered spring provides a broader seating on the diaphragm, which would seem to be an advantage.

kenzen
66 Monza Coupe 110/PG
Bel Air, MD

Options: ReplyQuote
Re: Mechanical Fuel Pump Observations...
Posted by: Richard ()
Date: March 17, 2018 07:54PM

With all this discussion about pumps, I have been wondering if there isn't a way to check for leaks and actual pressure, without installing the pump.

With what I have done so far, I've merely managed to come up with more questions than useful information.
I am trying to use an old 110 RD engine, but the few measurements I've made so far almost indicates I may have a mismatch of rod and pump parts.
In the picture, I have a pump assembled without a spring. With no spring, tightening the screws with the diaphragm and oil seal in a relaxed position, severely limits the travel.
I measured the travel on this RD engine push rod at .154". With my modified pump, with spring, it measured .109" ? I had marked the pulley at the lowest spot on the crank, pump cam. When checking the pump travel, I had to turn the crank aprox 45 deg before the diaphragm began to move?

Too chilly out there tonight. I'll take closer look later next week.

So far, the only thing positive about my pressure gauge setup is that it can check for leaks. I can push more pressure through it than the pump is capable of producing on its own. The diaphragm does seem to start moving at roughly 5 psi, but I'm going to have to give this some more thought before it's of any value.

Attachments:

Options: ReplyQuote
Re: Mechanical Fuel Pump Observations...
Posted by: impadjoe ()
Date: March 25, 2018 11:08AM

What were the different height measurements of the 3 springs when not compressed?

Options: ReplyQuote
Re: Mechanical Fuel Pump Observations...
Posted by: impadjoe ()
Date: March 25, 2018 11:14AM

Are you cutting the coil from the bottom or top? Thanks.

Options: ReplyQuote
Re: Mechanical Fuel Pump Observations...
Posted by: kenzen ()
Date: March 25, 2018 12:28PM

Richard,
I've been meaning to reply to your post above WRT the "test while installed" question. Your observations on the diaphragm behavior again asks the question - if the material has reinforcement threads woven in, how much "stretch" can we expect - none in my mind. So if standard assembly doesn't provide some slack by pushing in the rod and THEN tightening the body screws, we asking for the material woven into the diaphragm to break, creating concentrated strains in the material, which would lead to premature failure. This would explain reports of pump failure in the first few days or weeks. Jim Brandberg raised this concern back on page 2 of this thread, where he also asked about calculating or measuring the preload - I believe you have the right rig set up to measure this.

Impadjoe - which springs are you referencing for cutting?

All - I'm waiting for some garage time this week to begin to profile my springs with my recently purchased postal scale, using the "drill press rig". I'm going to plot the tension on graphs so we can see the behavior.

Ken

kenzen
66 Monza Coupe 110/PG
Bel Air, MD

Options: ReplyQuote
Re: Mechanical Fuel Pump Observations...
Posted by: JimBrandberg ()
Date: March 25, 2018 02:12PM

I listed the free lengths of my 4 springs tested earlier.

Jim Brandberg
Isanti, MN
CorvairRepair.com

Options: ReplyQuote
Re: Mechanical Fuel Pump Observations...
Posted by: JimBrandberg ()
Date: April 12, 2018 05:24AM

My interest and contribution to this thread was to hopefully find an in-stock spring somewhere to reduce pressure. It seems that we've run out of steam searching for that. Cutting and reforming springs seems crude to me but I guess that's what we've got. I found tapered springs a lot harder to search for than regular springs on spring company websites.

Does someone have pictures of before and after springs? I've generally been cutting a full coil off the big end and trying to reform flat. It seems to make the spring A LOT shorter. I suppose I have several springs I could practice up on and measure spring weights now that I have a suitable scale. I wish I had more time.

Some folks are of the opinion that Rochesters usually don't have trouble with the higher pressure. At least the turbo cars have a little more room to install a pressure regulator.

Jim Brandberg
Isanti, MN
CorvairRepair.com

Options: ReplyQuote
Re: Mechanical Fuel Pump Observations...
Posted by: Brizo ()
Date: April 12, 2018 10:54AM

I just had the opportunity to test and inspect a new Carter(NAPA) pump. Out of the box it would pump AND HOLD 9 in. of vacuum. The ability of your pump to hold vacuum "between strokes" is vitally important to its ability to overcome any tendency to vapor lock. Output was 7.5 psi which is about 3 psi less than most new pumps I've tested the last couple years. So this pump would work OK if it were installed as is. But an internal inspection revealed that although both valves were staked in the bores, they were not pressed down against their gaskets which allowed some leakage around the valve OD. The base casting had a machined gasket surface but the valve body did not. I always cut one coil from the top of the springs then reshape the last half coil so that it sets against the cover squarely. If available, I transfer new pumps to an original stiff aluminum A/C base because the zinc alloy bases warp easily causing internal leakage and pump failure. It now pumps 4.5 psi. and produces 11 in. of vacuum.

Dan Brizendine,
'64 8door Greenbrier 140 PG. "In beautiful Wanamaker Indiana...with one stop light and 5 pizza shops"

Options: ReplyQuote
Re: Mechanical Fuel Pump Observations...
Posted by: kenzen ()
Date: April 12, 2018 06:08PM

Brizo Wrote:
-------------------------------------------------------
> I just had the opportunity to test and inspect a
> new Carter(NAPA) pump. Out of the box it would
> pump AND HOLD 9 in. of vacuum. The ability of your
> pump to hold vacuum "between strokes" is vitally
> important to its ability to overcome any tendency
> to vapor lock. Output was 7.5 psi which is about 3
> psi less than most new pumps I've tested the last
> couple years. So this pump would work OK if it
> were installed as is. But an internal inspection
> revealed that although both valves were staked in
> the bores, they were not pressed down against
> their gaskets which allowed some leakage around
> the valve OD. The base casting had a machined
> gasket surface but the valve body did not. I
> always cut one coil from the top of the springs
> then reshape the last half coil so that it sets
> against the cover squarely. If available, I
> transfer new pumps to an original stiff aluminum
> A/C base because the zinc alloy bases warp easily
> causing internal leakage and pump failure. It now
> pumps 4.5 psi. and produces 11 in. of vacuum.

Sounds like you have this to a science! The machining of the gasket surfaces (or the lack there of) is a big deal, especially combined with screws that back out. I've been really busy with family challenges (sucks when parents get old), but I'm queued up in the garage to spec out some springs, and I have a second older pump from evilbay to compare springs to as well.
Ken

kenzen
66 Monza Coupe 110/PG
Bel Air, MD

Options: ReplyQuote
Re: Mechanical Fuel Pump Observations...
Posted by: JimBrandberg ()
Date: April 13, 2018 05:02AM

I'll try cutting the top of the spring instead of the bottom.

How do you test the vacuum? I've never considered that.

It's good to know that Carter is still making pumps too. Is it easy to tell that it's a Carter and not an Airtex?

Jim Brandberg
Isanti, MN
CorvairRepair.com

Options: ReplyQuote
Re: Mechanical Fuel Pump Observations...
Posted by: Brizo ()
Date: April 14, 2018 08:11AM

Jim, I have a brass fitting with a 5/32 hose nipple on it that I screw in the pump and attach a vacuum gage. I don't know where it came from but I think I've seen plastic fittings like it made for bleeding master cylinders.

Dan Brizendine,
'64 8door Greenbrier 140 PG. "In beautiful Wanamaker Indiana...with one stop light and 5 pizza shops"

Options: ReplyQuote
Re: Mechanical Fuel Pump Observations...
Posted by: Brizo ()
Date: April 14, 2018 01:07PM

Forgot this earlier Jim--
I think the Carter and Airtex are the same pump. It had the hex screws, "made USA" on top, and 4886 tag. They looked identical to me.

Dan Brizendine,
'64 8door Greenbrier 140 PG. "In beautiful Wanamaker Indiana...with one stop light and 5 pizza shops"



Edited 2 time(s). Last edit at 04/14/2018 01:51PM by MattNall.

Options: ReplyQuote
Re: Mechanical Fuel Pump Observations...
Posted by: JimBrandberg ()
Date: April 15, 2018 06:52AM

I hope it's not a dumb question but when checking vacuum are you turning it over with the starter or just pushing down on the bench, like when doing the wocka-wocka test?

Jim Brandberg
Isanti, MN
CorvairRepair.com

Options: ReplyQuote
Re: Mechanical Fuel Pump Observations...
Posted by: Brizo ()
Date: April 15, 2018 12:54PM

Jim, You can do it either way but its quicker by hand. How much vacuum it produces is good to know but what's more important is, will it hold between strokes. Remember, it only has to pump gas about 2 feet, it has to suck it about 10 feet and up hill!

Dan Brizendine,
'64 8door Greenbrier 140 PG. "In beautiful Wanamaker Indiana...with one stop light and 5 pizza shops"

Options: ReplyQuote
Current Page: 4 of 6


Sorry, only registered users may post in this forum.
This forum powered by Phorum.