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Brake reservoir not on firewall?

dwranda

Well Known Member
I have searched for answers to my questions but didn't really come up with anything. What is the reason that the brake reservoir is on the firewall? Has anyone with a 6,7,or 9 tip up put the reservoir on the sub panel that is accessible when the canopy is up? I am trying to not have anything aluminum on the firewall and would like to know if there would be any negatives locating it where I said. I have seen those with 8's putting them somewhere other than the firewall, but haven't found any 6,7,or 9's. I am not really interested in the pedal mounted reservoirs since that would be more to buy and I already have the Vans reservoir.
 
Brake reservoir location and type is a personal preference just like underwear and headset.

I paid extra to put my RV-6 brake reservoir on the engine side of the firewall more than two decades ago. I have found 5606 or the synthetic replacement MIL-H-83282 to be messy and leaves a sticky mess when spilled or splash out of its container. I do not want to have to clean the mess out of the cockpit. It is much less messy to clean off the firewall.

The reservoir that I fitted to the engine side of the firewall cannot be completely filled else in turbulence, it splashes out and makes a mess. What ever reservoir one uses needs to allow room for expansion and splashing around. I have found that for my airplane any level between 1/2 and 2/3 will work. Typically I do not add any additional fluid unless it is below 1/2 and at any time it is above 2/3, I remove some fluid.
 
I'm not flying yet, but I did basically what you describe. Others have mentioned using reservoirs attached to the brake cylinders, an option available, IIRC, from the brake mfgrs.

Charlie
 
I was wondering the same, and planning on holding off mounting the reservoir until I know where it can fit under the cowl, so it is accessible with tip up open
 
Nothing real wrong with mounting the reservoir high on the engine side of the firewall. Obviously plumbing the reservoir outlet with a plastic fitting through the firewall is a risk, but that's easy enough to correct. Same for plastic fluid lines against the back side of the firewall.
 
I'd rather not have the flammable hydraulic fluid on the cabin side of the firewall. And like RV6_flyer said, it can be a real mess when some gets out of the container. Which it will, sometime or other.

Dave
 
Brake reservoir location and type is a personal preference just like underwear and headset.

I paid extra to put my RV-6 brake reservoir on the engine side of the firewall more than two decades ago. I have found 5606 or the synthetic replacement MIL-H-83282 to be messy and leaves a sticky mess when spilled or splash out of its container. I do not want to have to clean the mess out of the cockpit. It is much less messy to clean off the firewall.

The reservoir that I fitted to the engine side of the firewall cannot be completely filled else in turbulence, it splashes out and makes a mess. What ever reservoir one uses needs to allow room for expansion and splashing around. I have found that for my airplane any level between 1/2 and 2/3 will work. Typically I do not add any additional fluid unless it is below 1/2 and at any time it is above 2/3, I remove some fluid.

I chased a mystery brake fluid leak for a long time on my airplane for exactly this reason - finally figured out I was simply overfilling it and it was dumping a little in turbulence or air in a line somewhere was burping a little out as I climbed into the upper teens. The fluid was following the brake lines to the pedals and dripping on the floor - looking for all the world like a leaking master cylinder. Drove me crazy for about 50 flight hours before I figured it out.
 
I'd rather not have the flammable hydraulic fluid on the cabin side of the firewall. And like RV6_flyer said, it can be a real mess when some gets out of the container. Which it will, sometime or other.
Dave

Which is why I mentioned that plastic firewall fitting. If the reservoir gets hot enough, it's going to drain into the cockpit.
 
A lot of builders install individual reservoirs directly on each master cylinder. Inside the cockpit.
This has been accepted for years and I personally have never seen any issues with leaks any more than with the basic master cylinder leaks you may get.
So, why not just mount the reservoir supplied by VANs on the cockpit side where it is easy to get at.
That?s what I?m going to do on my 3.
Although, I will say I don?t really care for the nylon fittings VANs supplies so I?ll use something different for that.
 
I'd rather not have the flammable hydraulic fluid on the cabin side of the firewall. And like RV6_flyer said, it can be a real mess when some gets out of the container. Which it will, sometime or other.

Dave

Is the amount of brake fluid in the lines in the cabin at any time way less than the amount that is in the reservoir? In your example having this fluid in plastic lines in the cabin must be a really bad idea. In an engine fire would the reservoir melt and cause the flammable liquid to ignite in the cabin lines? If the reservoir were in the cabin what could possibly cause it to ignite? If it's that hot in there to melt the reservoir I would think you are toast anyways.
Am I way off in my thinking? Trying to learn all I can here!
 
Brake reservoir Cap

Firewall for all the reasons in above posts. When servicing I don't think you'd want to clean up any spills in the cockpit. As previously stated, firewall is easier to wipe down. The reservoir cap as noted, https://www.vansaircraft.com/cgi-bin/store.cgi?ident=1521548597-414-492&browse=am&product=b-caps works well and a buddy of mine showed me a trick to keep the reservoir cap dry when inverted. Take a piece of clear tubing of a size that fits snugly over the cap when in place on top of the reservoir. Cut it long enough fit a piece of wadded up cotton ball inside which will absorb the brake fluid when you're inverted and keep any from leaking out, replace with new cotton ball periodically. Granted it would eventually get saturated enough to dribble out but you'd have to be inverted for quite a while for this to be an issue. Been doing this for years and do a fair amount of aerobatics, the cap never seeps.
 
A lot of builders install individual reservoirs directly on each master cylinder. Inside the cockpit.
This has been accepted for years and I personally have never seen any issues with leaks any more than with the basic master cylinder leaks you may get.

Just as an aside...when my buddy built his -8, he put the reservoirs directly on the master cylinders. He HATES it now...because checking and/or refilling the reservoirs means crawling down into the footwell each time (awkward to get to, poor lighting, etc.).

YMMV.
 
Just as an aside...when my buddy built his -8, he put the reservoirs directly on the master cylinders. He HATES it now...because checking and/or refilling the reservoirs means crawling down into the footwell each time (awkward to get to, poor lighting, etc.).

YMMV.

I'd agree. I wouldn't do that, even in my -7, because of the hassle in servicing the reservoirs. I only mentioned it in my post to show that having the reservoir in the cockpit is not a crazy idea.

To those who worry about spillage: If you have inverted systems on your a/c and fly actual sustained negative G maneuvers, you probably need to worry about spillage. (But not as much as choice of airframe... :) ) But for typical RV flying, even acro flying, spillage shouldn't be an issue. Over almost 25 years of RV-4 ownership, I've lost far more fluid from leaks in supply lines than I've ever lost out the cap that Van supplies with the reservoir. I spill more when filling through that tiny opening than I ever see outside the reservoir after acro.

FWIW...

Charlie
 
Just as an aside...when my buddy built his -8, he put the reservoirs directly on the master cylinders. He HATES it now...because checking and/or refilling the reservoirs means crawling down into the footwell each time (awkward to get to, poor lighting, etc.).

YMMV.

Yep!

My non-RV has those and it's a messy, painful job to check or service these. Ugh.

Dave
 
It's always interesting how the winds of change blow too and fro.....

30 years ago, a standard RV-4 or 6 kit included an individual reservoir to put on each master cyl. in the cockpit.

Changing to a firewall mounted one was probably one of the earliest 'factory options' available for an RV kit, and it was eventually incorporate as standard in the kits because everyone heard how much of a pain the individual ones were and ordered it.

:confused:
 
The fluid level in the reservoir (standard location) on my RV-9A doesn't change perceptibly between oil changes. Not too difficult to check the level through the oil filler door...a tie-wrap makes a good dipstick.

As for topping it off, I'd rather remove the easily removable top cowling than do the "panel dive" to replenish MC-mounted reservoirs, and avoid risking spills of brake fluid on the carpet.
 
On my RV4 I put the reservoir on the firewall in the centre and to make removal and installation of the upper cowl easier I have an access opening at the rear of the top cowl, so that I can put the wires into the piano hinges easily. It also allows easy checking of the brake reservoir.
 
Just as an aside...when my buddy built his -8, he put the reservoirs directly on the master cylinders. He HATES it now...because checking and/or refilling the reservoirs means crawling down into the footwell each time (awkward to get to, poor lighting, etc.).

YMMV.

I know that the OP already rejected the individual reservoirs, and that?s a fair decision for anyone to make. However, for future readers of this thread, I would like to point out that I have four airplanes with individual reservoirs, they work great, don?t leak (with the vented cap) and I never crawl under the panel to service them. We pump up he brake systems from the bottom in a fill/bleed pertain, know how much fluid it is going to take, and never overfill or make a mess.

Guess that I am just doing it wrong, according to all those who think they are a pain or won?t work.....;)

Paul
 
Another Data Point

The Glasair Glastar and Sportsman both have the Matco clear reservoir mounted high on the cool side of the firewall. Granted, the Sportsman is not designed to fly upside down, but that part could be resolved in a similar manner to what was mentioned in post # 15 above. Tape a cotton ball over the vent opening which will allow air to move in and out but will catch any fluid sneaking out the hole. Plus, the reservoir does not have to be full. The picture below is from my Sportsman and I flew at that level for a long time. No fluid went anywhere.

Also granted access is much (MUCH) easier in the Sportsman, but in the -8 you could do something similar and run the reservoir above the front baggage floor and mount it to the inside of the firewall where it can be accessed through the baggage door. No diving required.

IMG_0787.small-M.jpg
 
The Glasair Glastar and Sportsman both have the Matco clear reservoir mounted high on the cool side of the firewall. Granted, the Sportsman is not designed to fly upside down, but that part could be resolved in a similar manner to what was mentioned in post # 15 above. Tape a cotton ball over the vent opening which will allow air to move in and out but will catch any fluid sneaking out the hole. Plus, the reservoir does not have to be full. The picture below is from my Sportsman and I flew at that level for a long time. No fluid went anywhere.

Also granted access is much (MUCH) easier in the Sportsman, but in the -8 you could do something similar and run the reservoir above the front baggage floor and mount it to the inside of the firewall where it can be accessed through the baggage door. No diving required.

IMG_0787.small-M.jpg

This is pretty much what I was asking about except instead of mounting on the firewall mounting it to an area accessible when the tip up is up. There are many mentions of it in the archives being done on 8's but have yet to see a pic under the tip up of a 6,7, or 9. Is that area just too clogged with electronics to find space to mount a reservoir?
 
This is pretty much what I was asking about except instead of mounting on the firewall mounting it to an area accessible when the tip up is up. There are many mentions of it in the archives being done on 8's but have yet to see a pic under the tip up of a 6,7, or 9. Is that area just too clogged with electronics to find space to mount a reservoir?

I've had an 8 with a reservoir inside the airplane for 750 hours, in this case tucked into a corner of the baggage compartment where it interferes with nothing. It is accessible while standing next to the airplane. I would think something similar could be done with a tip up.

There are no plastic lines near the firewall. A red hot firewall will turn a plastic line full of flammable fluid into a fire transfer device, bringing an engine compartment fire into the cockpit. It's also true of steel-braided line, which is just a plastic line with a braid cover.

That's not to say steel-braided lines are bad. They're not, in particular since they terminate with AN flare fittings, not compression fittings squeezing on plastic. Opinions vary, but considering we go 80 miles an hour on a dead-end street, with gas in tanks that would make a '76 Pinto proud, well...maybe the best hardware is just good enough. Personally I reserve plastic line and compression fittings for the slow and very light.

10x62s6.jpg
 
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Thanks Dan! That's a great example of what it may look like under the tip up. I am going to be doing the fiberfrax and foil treatment to the engine side of the firewall as well. I have learned a lot from your testing of various products and posting the results. Much appreciated!!
 
Brake Lines

You might want to rethink your brake line installation if your plans show a tee on firewall side and a line running all the way across the bottom of firewall on engine side just as easy to have a bulkhead fitting on each side of firewall and separate lines running down each leg if your building a tailwheel model.
Bob
 
Thanks Dan! That's a great example of what it may look like under the tip up. I am going to be doing the fiberfrax and foil treatment to the engine side of the firewall as well. I have learned a lot from your testing of various products and posting the results. Much appreciated!!

dwranda,

I mounted mine (tipup -7) to the right side panel support rib, just aft of the subpanel. If you want pics, pm me your email address.

Charlie
 
We pump up he brake systems from the bottom in a fill/bleed pertain, know how much fluid it is going to take, and never overfill or make a mess.

Paul,
Does this video adequately describe your method? https://www.youtube.com/watch?v=bZlq87VXybU

I'm leaning toward the pedal mount reservoirs myself. I'm assuming I only two pedal mounted reservoirs for an RV-7 dual brake system (one per side) and not four (one per pedal). Correct?

Thanks,
 
I am trying to not have anything aluminum on the firewall

You'll need to re-think your engine choice if planning a Lycoming engine. You do know that much of the engine, including the entire crankcase, is aluminum right?

Larry
 
You'll need to re-think your engine choice if planning a Lycoming engine. You do know that much of the engine, including the entire crankcase, is aluminum right?

Larry

I get that, but the point is to not have anything thin that can easily burn through quickly and emit gasses or flames to the cabin. I imagine you know that though and your statement was a little tongue in cheek!! :D
 
Dave,

I tend to agree with dwranda; that's why I mounted mine slightly aft of the sub-panel, on the panel brace rib (tipup -7). Firewall mounting creates a hole in the stainless, that's plugged with an aluminum fitting connected to a plastic line. Even with no fire in the equation, still an extra penetration that could leak gasses. The location I chose can be accessed with the canopy up, so no need to remove the cowl or dive under the panel.

My -4 has it on the hot side of the firewall, and it's a pain to fill because it's tight against the firewall, and up near the top flange. I now use disposable syringes to transfer fluid from its container to the reservoir (after removing the top cowl).

Charlie
 
If you are worried about in-flight spills, you could change to an automotive-style reservoir. I made the change because I swapped my system to DOT4 fluid, but the reservoir would work either way. This reservoir has a diaphragm under the cap, so no spills. Plus the opening is larger/easier to fill.

FP14042012A0004T.jpg
 
Reservor on the brake cylinder 👍

Paul Dye advised me on my 3B build that he had good results with the cylinder mounted reservoir . I use TS flightlines stainless hose and firewall bulkhead fittings. Fill from the bottom like Paul suggests. No leaks, no burps. Check fluid at condition inspection with the boot cowl off anyway.
 
FWIW, I used the master cylinder-mounted reservoirs on my -8 (completed 5/02) and never had an issue. I plan to use them on the new -14A, too.
 
That's what the firewall is there to prevent.

I'd rather have it be there than in the cabin.

Perhaps...if the firewall penetration is gas tight and melt-proof (i.e. a steel bulkhead fitting), and if the line from the firewall penetration to the master cylinders will withstand a red hot firewall in close proximity.

Plastic lines full of flammable liquid, placed against the cabin side of a firewall, have the potential to be a fire transfer device.

If you are worried about in-flight spills, you could change to an automotive-style reservoir....This reservoir has a diaphragm under the cap, so no spills.
FP14042012A0004T.jpg

Nice pick! Would be great aft of the firewall. Easy fill, no spill.
 
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