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Matt Dralle
Site Admin
Joined: 08 Nov 2005
Posts: 25203
Location: Livermore CA USA
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 Posted: Tue Oct 28, 2008 5:48 pm Post subject: Question On Low-Pressure Brake Lines... |
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Dear Listers,
I spent a lot of time staring at those plastic brake lines for the low pressure side and just didn't like a thing about them. Just imagine if one were to break and what a mess all the brake fluid all over the cockpit would be like.
After some thought, I came up with the following system for the low pressure feed. I used standard AN 1/4" fittings and aluminum tubing to bring the fluid from the reservoir to a tee fitting and then to bulkhead fittings that connect to standard Aeroquip hoses to the master calendars. Yeah, it was a little more weight, but the peace of mind is worth it.
But here's my question. Notice that on the back side of the second bulkhead, I kind of looped the tubing up and around the hole for the vent. This also positioned tee fitting nicely to feed the left and right sides. The top of that loop is maybe 4 to 5" higher than the top of the reservoir, though. Is the flow from the reservoir to the master cylinders suppose to be basically "gravity fed" or is the "pump" action from the master cylinders all that is necessary to keep the tube and master cylinders full?
Matt Dralle
RV-8 #82880 N844RV (res)
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rice737(at)msn.com
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| Posted: Tue Oct 28, 2008 6:48 pm Post subject: Question On Low-Pressure Brake Lines... |
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Hey Matt C
Your work looks great. To the best of my knowledge C the reservoir should be above the master cylinders. I have been using the small resevoirs that attach to the top of the master cylinders with no problems. Have you given them any thought?
Paul Rice
RV8 110 hours
Flying Siren
| Quote: | Date: Tue C 28 Oct 2008 18:48:08 -0700
To: rv8-list(at)matronics.com; rv-list(at)matronics.com
From: dralle(at)matronics.com
Subject: Question On Low-Pressure Brake Lines...
Dear Listers C
I spent a lot of time staring at those plastic brake lines for the low pressure side and just didn't like a thing about them. Just imagine if one were to break and what a mess all the brake fluid all over the cockpit would be like.
After some thought C I came up with the following system for the low pressure feed. I used standard AN 1/4" fittings and aluminum tubing to bring the fluid from the reservoir to a tee fitting and then to bulkhead fittings that connect to standard Aeroquip hoses to the master calendars. Yeah C it was a little more weight C but the peace of mind is worth it.
But here's my question. Notice that on the back side of the second bulkhead C I kind of looped the tubing up and around the hole for the vent. This also positioned tee fitting nicely to feed the left and right sides. The top of that loop is maybe 4 to 5" higher than the top of the reservoir C though. Is the flow from the reservoir to the master cylinders suppose to be basically "gravity fed" or is the "pump" action from the master cylinders all that is necessary to keep the tube and master cylinders full?
Matt Dralle
RV-8 #82880 N844RV (res)
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[quote][b]
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rv8iator
Joined: 11 Apr 2006
Posts: 145
Location: Newberg, OR
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| Posted: Wed Oct 29, 2008 6:09 am Post subject: Question On Low-Pressure Brake Lines... |
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Matt...
RV's have been using the nylon brake supply tube for years with few problems. The issue that may give you a problems is when bleeding... Being able to see the bubbles in the supply lines make it possible to purge them. I admit that I have a sample size of one... but, we had a tough time getting all the bubbles out even when we could see them.
Chris Stone
RV-8
Newberg, Oregon
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flyinwithme99(at)yahoo.co
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| Posted: Wed Oct 29, 2008 6:56 am Post subject: Question On Low-Pressure Brake Lines... |
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The important thing is to have the reservoir higher than any of the feed lines. Having all the bubbles out of the feed lines is not necessary as long as you have enough head for a positive fluid flow to the master cylinders. You may have a problem with an air lock in some of the loops you created in the feed lines. Pressure bleeding the system from the bottom up should purge enough of the feed lines to have a sufficient solid reservoir of fluid for feeding the master cylinders when they need additional fluid.
Remember that the only time the master cylinders need any additional fluid is to compensate for brake wear.
From: Matt Dralle <dralle(at)matronics.com>
To: rv8-list(at)matronics.com; rv-list(at)matronics.com
Sent: Tuesday, October 28, 2008 8:48:08 PM
Subject: Question On Low-Pressure Brake Lines...
Dear Listers,
I spent a lot of time staring at those plastic brake lines for the low pressure side and just didn't like a thing about them. Just imagine if one were to break and what a mess all the brake fluid all over the cockpit would be like.
After some thought, I came up with the following system for the low pressure feed. I used standard AN 1/4" fittings and aluminum tubing to bring the fluid from the reservoir to a tee fitting and then to bulkhead fittings that connect to standard Aeroquip hoses to the master calendars. Yeah, it was a little more weight, but the peace of mind is worth it.
But here's my question. Notice that on the back side of the second bulkhead, I kind of looped the tubing up and around the hole for the vent. This also positioned tee fitting nicely to feed the left and right sides. The top of that loop is maybe 4 to 5" higher than the top of the reservoir, though. Is the flow from the reservoir to the master cylinders suppose to be basically "gravity fed" or is the "pump" action from the master cylinders all that is necessary to keep the tube and master cylinders full?
Matt Dralle
RV-8 #82880 N844RV (res)
[quote][b]
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James Baldwin
Joined: 16 Jan 2006
Posts: 23
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| Posted: Wed Oct 29, 2008 9:03 am Post subject: Question On Low-Pressure Brake Lines... |
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Matt-
Surely you are using one of the "reverse flow", one man brake bleeding
external reservoirs? With it, the external source of brake fluid is forced
back through the calipers, up the pressurized supply lines, through the
master cylinders, up the un-pressurized feed lines and into the reservoir,
spilling out the top into a temporary catch can. There is no possible
bubble in any line. Works great, available at ACS. JBB
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mdw(at)ceoexpress.com
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| Posted: Wed Oct 29, 2008 12:46 pm Post subject: Question On Low-Pressure Brake Lines... |
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Could you please delete me from the RV list?
I am going in a different direction.
David Wilder
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willslau(at)comcast.net
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| Posted: Wed Oct 29, 2008 3:32 pm Post subject: Question On Low-Pressure Brake Lines... |
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David, you have to do that yourself. Look at the instructions at the bottom of the post.
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Matt Dralle
Site Admin
Joined: 08 Nov 2005
Posts: 25203
Location: Livermore CA USA
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| Posted: Sat Nov 01, 2008 5:03 pm Post subject: Question On Low-Pressure Brake Lines... |
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Dear Listers,
After some head scratching and a couple more tries, I think I came up with a new design for the low pressure side of the brake lines. With this design, there is a steady slope downward from the reservoir to the master calendars. Seems to be pretty substantial. My only concern is that right feed line going through that candy cane piece isn't really supported anywhere. Its pretty short and solid to the touch, but vibration might cause a issue. Since the bottom floor of the baggage area goes over the top, there's really nothing permanent I can attach it to short of making a bracket of some kind (yuck).
So what do you guys think?
Matt Dralle
RV-8 #82880 N844RV (res)
At 06:48 PM 10/28/2008 Tuesday, Matt Dralle wrote:
| Quote: | [snip]
But here's my question. Notice that on the back side of the second bulkhead, I kind of looped the tubing up and around the hole for the vent. This also positioned tee fitting nicely to feed the left and right sides. The top of that loop is maybe 4 to 5" higher than the top of the reservoir, though. Is the flow from the reservoir to the master cylinders suppose to be basically "gravity fed" or is the "pump" action from the master cylinders all that is necessary to keep the tube and master cylinders full?
Matt Dralle
RV-8 #82880 N844RV (res)
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| | - The Matronics RV8-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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johnee35(at)att.net
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| Posted: Sun Nov 02, 2008 7:08 am Post subject: Question On Low-Pressure Brake Lines... |
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It's an experimental aircraft, your idea will probably work fine, try it.
Or use the flex lines as plans call for, or use the reservoirs on the master
cylinders to assure no leaks.
The amount of fluid needed to keep calipers working properly won't amount to
1 ounce per side as lining wears.
I used the flex lines per plans, two years, 200 hours, no problem.
J.Ellis a/p 1726833
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Matt Dralle
Site Admin
Joined: 08 Nov 2005
Posts: 25203
Location: Livermore CA USA
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| Posted: Sun Nov 02, 2008 9:20 am Post subject: Question On Low-Pressure Brake Lines... |
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Thank you for the feedback John. To run it parallel with the high pressure line above it, I would have had to go up a couple of inches as it relates to the reservoir since I have to go under the baggage floor. I was trying to make sure that all of the run was at least slightly downward to keep gravity pulling the fluid toward the master cylinder. Am I mis-understanding your comment?
Matt
At 08:54 AM 11/2/2008 Sunday, you wrote:
[quote]Your workmanship is exceptional and a thing of beauty to behold.
However, when I am performing Tech Inspections, I would caution builders
on the use of a long continuous run as in your picture (2). I would
have created the same sweep as the line above and run the straight line
more parallel to the upper line.
John Cox
A&P, IA
EAA Tech #5242
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Matt Dralle
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Matt Dralle
Site Admin
Joined: 08 Nov 2005
Posts: 25203
Location: Livermore CA USA
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| Posted: Sun Nov 02, 2008 9:28 am Post subject: Question On Low-Pressure Brake Lines... |
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Ah! I understand. But those are the low pressure side so there really isn't any "pressure" to speak of, is there? I do see your point from a best-practices stand point and it was something that I didn't know.
Thanks!
Matt
At 09:23 AM 11/2/2008 Sunday, you wrote:
[quote]No, however any line containing pressurized fluid contracts in length
and expands in diameter, hence the need for flex by routing other than
the "shortest distance between two connection points. It is spelled out
in the AC43.13.
John
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Matt Dralle
Site Admin
Joined: 08 Nov 2005
Posts: 25203
Location: Livermore CA USA
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| Posted: Sun Nov 02, 2008 9:53 am Post subject: Question On Low-Pressure Brake Lines... |
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Thanks for the tip, Mike. I actually did try these babies out. The problem on the RV-8, though, is that with the adjustable rudder pedals at full "tall-person", the mini-reservoir doesn't clear the firewall when the brakes are applied. Here's a picture with one on the right master cylinder and full right rudder applied, but no brake action. Notice that there is only about 1/16" of clearance to the firewall. I wish that Grove had used a different fitting design instead of just slapping a NPT M-M on the side. Its way too long. Anybody know of a similar fitting that is about half as long?
Matt
At 06:46 PM 11/1/2008 Saturday, you wrote:
| Quote: |
Hi Matt,
You've created a plumbing masterpiece but it's a ton of complication and cost. Have you thought about just mounting the brake reservoir right on the brake master cylinders?
This is similar to the set up that I've used. $22/ea.
Good luck.
http://www.aircraftspruce.com/catalog/lgpages/remoteFluidReservoirs.php
>Dear Listers,
>
>After some head scratching and a couple more tries, I think I came up with a new design for the low pressure side of the brake lines. With this design, there is a steady slope downward from the reservoir to the master calendars. Seems to be pretty substantial. My only concern is that right feed line going through that candy cane piece isn't really supported anywhere. Its pretty short and solid to the touch, but vibration might cause a issue. Since the bottom floor of the baggage area goes over the top, there's really nothing permanent I can attach it to short of making a bracket of some kind (yuck).
>
>So what do you guys think?
>
>Matt Dralle
>RV-8 #82880 N844RV (res)
>
Matt G Dralle | Matronics | PO Box 347 | Livermore | CA | 94551
925-606-1001 V | 925-606-6281 F | dralle(at)matronics.com Email
http://www.matronics.com/ WWW | Featuring Products For Aircraft
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speed3guy(at)comcast.net
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| Posted: Sun Nov 02, 2008 12:05 pm Post subject: Question On Low-Pressure Brake Lines... |
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Matt,
I used the individual reservoirs, but mounted them with a street elbow
instead of a straight nipple. That gives a bit more clearance to the
firewall.
Guy
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