VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics


Go Back   VAF Forums > Main > RV General Discussion/News
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #51  
Old 12-02-2011, 01:37 PM
DanH's Avatar
DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
Posts: 9,500
Default

Quote:
Originally Posted by rocketbob View Post
Cool. Looks like all you would need is the meter, two resistors, and a 9V battery clip. It's only 200mV full scale straight out of the box, but the data sheet lists the two resistor values necessary to re-scale. I guess you would have to go to a 20V scale as 2V isn't enough for the expected temperatures @ 10mV/degreeF from the LM34.

Thanks Bob.

Speaking of the LM34....any necessary filtering, etc, or is it good to go with the very basic wiring?
__________________
Dan Horton
RV-8 SS
Barrett IO-390
Reply With Quote
  #52  
Old 12-02-2011, 03:42 PM
rocketbob's Avatar
rocketbob rocketbob is offline
 
Join Date: Jun 2006
Location: 8I3
Posts: 3,564
Default

Shouldn't really need anything else with the LM34 as long as you use twisted pair.

In the -6 I used the 2V range off the Electroair since it put out 10mV/degree advance, so the 2V range was sufficient. Just make sure you use precision 1% resistors. But in this case if your measuring 300 deg. the output is going to be 3V, obviously you'll need to set the divider resistors to 20V.
__________________

Please don't PM me! Email only!

Bob Japundza CFI A&PIA
N9187P PA-24-260B Comanche, flying
N678X F1 Rocket, under const.
N244BJ RV-6 "victim of SNF tornado" 1200+ hrs, rebuilding
N8155F C150 flying
N7925P PA-24-250 Comanche, restoring
Not a thing I own is stock.
Reply With Quote
  #53  
Old 12-02-2011, 03:47 PM
lostpilot28's Avatar
lostpilot28 lostpilot28 is offline
 
Join Date: Nov 2006
Location: Boise, ID
Posts: 1,095
Default

Quote:
Originally Posted by DanH View Post
So, Sonny, you started the thread. What exactly do you want to determine or accomplish?
The end result is that I want to increase my cooling capability in hot weather and (hopefully...potentially) decrease my cooling drag. I want to do it without cutting holes in my lower cowl for louvers.

Hopefully, measuring the upper and lower cowl pressure shows that there isn't enough differential pressure (whatever that may be). Right now I can think of 2 potential things to improve to assist in lowering the pressure in the bottom half of the cowl. 1 - I still have a gap behind my spinner that dumps air into the lower cowl, and 2 - my FAB carb heat flap may not be closing all the way. I've done everything else I can think of to improve the airflow, and thus the cooling of my oil temps. I've closed every other gap in my plenum and baffling, and I've increased my oil cooler to a 10-row cooler and increased size of the hole that feeds air to the cooler.

Crossing my fingers it'll be that easy...
__________________
Sonny W
Boise, Idaho
RV-7A Flying!
Reply With Quote
  #54  
Old 12-02-2011, 03:53 PM
LifeofReiley's Avatar
LifeofReiley LifeofReiley is offline
 
Join Date: Jan 2005
Location: Round Rock, TX
Posts: 3,778
Default

Quote:
Originally Posted by lostpilot28 View Post
and 2 - my FAB carb heat flap may not be closing all the way...
Hmmm more details here... the FAB should be sealed to the front of the cowl, lost on the flap not closing all the way, maybe I missed something somewhere. If you're talking about the top of the FAB to the stock Van's carb heat muff... I really don't this that's your issue.
__________________
Reiley
Retired N622DR - Serial #V7A1467
VAF# 671
Repeat Offender / Race 007
Friend of the RV-1

Last edited by LifeofReiley : 12-02-2011 at 04:08 PM.
Reply With Quote
  #55  
Old 12-02-2011, 04:01 PM
CMW CMW is offline
 
Join Date: Mar 2007
Location: Livermore, CA
Posts: 167
Default

Quote:
Originally Posted by DanH View Post
Speaking of the LM34....any necessary filtering, etc, or is it good to go with the very basic wiring?
Dan, I would at least put a .1uF bypass cap right at the sensor. Hook it between the sensors V+ input and GND. It will ensure a clean voltage powering the sensor.

-Chris
__________________
Chris
RV-8 Wings
Reply With Quote
  #56  
Old 12-02-2011, 04:35 PM
Tom Martin Tom Martin is offline
 
Join Date: Jan 2005
Location: Ontario, Canada
Posts: 1,544
Default

Quote:
1 - I still have a gap behind my spinner that dumps air into the lower cowl,
Actually, just the opposite is happening here. The upper cowling pressure is higher then the lower cowling pressure. The lower cowling pressure is higher then the outside air. If this was not the case then air would not flow through the cowling. Thus air from the lower cowling tries to get out where ever it can, the exit air area, around the cowling attach points, at the gear farings and around the spinner cut out.
The problem with air escaping from spinner is that aside from causing drag it upsets the airflow into the cowling inlets.
This has been discussed before and I am sure you will be able to find some different examples of how people have reduced and/or sealed this area.
__________________
Tom Martin RV1 pilot 4.6hours!
CPL & IFR rated
EVO F1 Rocket 1000 hours,
2010 SARL Rocket 100 race, average speed of 238.6 knots/274.6mph
RV4, RV7, RV10, two HRIIs and five F1 Rockets
RV14 Tail dragger

Fairlea Field
St.Thomas, Ontario Canada, CYQS
fairleafield@gmail.com
Reply With Quote
  #57  
Old 12-02-2011, 04:50 PM
lostpilot28's Avatar
lostpilot28 lostpilot28 is offline
 
Join Date: Nov 2006
Location: Boise, ID
Posts: 1,095
Default

Quote:
Originally Posted by LifeofReiley View Post
Hmmm more details here... the FAB should be sealed to the front of the cowl, lost on the flap not closing all the way, maybe I missed something somewhere. If you're talking about the top of the FAB to the stock Van's carb heat muff... I really don't this that's your issue.
Yep, talking about the flap that opens to the carb-heat muff. When it's in the "no-carb-heat" position, it doesn't sit completely flush. I doubt it's the problem, too...just not 100% sure.

Quote:
Originally Posted by Tom Martin View Post
Actually, just the opposite is happening here. The upper cowling pressure is higher then the lower cowling pressure. The lower cowling pressure is higher then the outside air. If this was not the case then air would not flow through the cowling. Thus air from the lower cowling tries to get out where ever it can, the exit air area, around the cowling attach points, at the gear farings and around the spinner cut out.
The problem with air escaping from spinner is that aside from causing drag it upsets the airflow into the cowling inlets.
This has been discussed before and I am sure you will be able to find some different examples of how people have reduced and/or sealed this area.
Hi Tom, yes I've seen the other posts on this...and you could be right. Although, I have the Sam James cowl and plenum, and I"m not sure how air flow could get disrupted flowing into those. Maybe it can...I just can't visualize it. Either way, after initial pressure testing, I plan on sealing that gap the same way Dan did...looks like an easy way to skin that cat, and I have a ton of pop-rivets left over!

The only other thing I can think of is that my exit air flow is restricted. I have the Vetterman 4-into-2 exhaust setup, but I also have a nosewheel gear leg and supporting mounts in the way.
__________________
Sonny W
Boise, Idaho
RV-7A Flying!
Reply With Quote
  #58  
Old 12-02-2011, 05:22 PM
DanH's Avatar
DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
Posts: 9,500
Default

Quote:
Originally Posted by Tom Martin View Post
The problem with air escaping from spinner...
Tom, consider the idea of flow both in and out. The CFD porn suggests a high pressure area below the spinner and a low pressure above it. I suspect air is entering the spinner gap at the bottom in all cases. What it does from there is dictated by lower plenum pressure and/or seal placement.

For cowls with extra large exits I suspect below-the-spinner pressure easily exceeds lower plenum pressure and a fair quantity of air enters the lower cowl.

Cowls with more conventional exits probably see some rather confused flow and a good bit of air exiting the spinner gap at the top.

Cowls with tight exits probably flow up from the bottom of the spinner and from inside the lower cowl.

And folks with sealed propshafts like you and Ken and I probably have no flow in or out of the cowl, but still have some useless flow behind the spinner....at least for now

Here's the thing....at this point in time we're talking about measuring, not guessing, and that's got to be all good.



Quote:
Originally Posted by lostpilot28 View Post
I have the Sam James cowl and plenum...
Sonny, it's going to be hugely interesting to get a set of pressure measurements on an SJ cowl.
__________________
Dan Horton
RV-8 SS
Barrett IO-390

Last edited by DanH : 12-02-2011 at 05:34 PM.
Reply With Quote
  #59  
Old 12-02-2011, 07:17 PM
lostpilot28's Avatar
lostpilot28 lostpilot28 is offline
 
Join Date: Nov 2006
Location: Boise, ID
Posts: 1,095
Default

Quote:
Originally Posted by DanH View Post
Sonny, it's going to be hugely interesting to get a set of pressure measurements on an SJ cowl.
Oh no! Now the pressure's on! I'm very interested, too...and despite looking like I don't know what I'm doing, I'll post it anyway. The friendly Chinese company said shipping will take around 15 business days! Doh! Stay tuned...I'll be routing hoses in the meantime...
__________________
Sonny W
Boise, Idaho
RV-7A Flying!
Reply With Quote
  #60  
Old 12-03-2011, 06:16 AM
DanH's Avatar
DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
Posts: 9,500
Default

Quote:
Originally Posted by lostpilot28 View Post
Stay tuned...I'll be routing hoses in the meantime...
You can run them through the cabin heat box or rig cheap bulkhead fittings.

I grabbed some 3/16" (10-32) all-thread rod from the scrap bin, cut short lengths, chucked them in the lathe, cut off the threads on each end to form a hose barb, and center-drilled them. Add two nuts and two washers and you have a miniature steel bulkhead fitting.

The yellow tygon tubing is available at the auto parts store as "small engine fuel line". It has good heat resistance. I don't know if clear vinyl tube will hold up but somebody might want to try it...it's cheap.

__________________
Dan Horton
RV-8 SS
Barrett IO-390
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
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

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 02:16 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.