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Geoff

Is anyone using flexible brake lines (stainless steel braided teflon hose) all the way from the fittings on the bottom of the fuselage down the gear legs to the brake calipers?

I've never liked the aluminum tubing setup, and now that I have it removed again (to torque the landing gear bolts -- ugh!), I'm considering replacing it with some hose from Bonaco. However, I'm concerned about chafing on the landing gear U-brackets. The alumimun tubing can be bent so it makes the transition from fuselage bottom to gear leg without touching anything, but it sure seems to me like a flexible line here would rub on that U-bracket.

Pictures would be helpful if anyone has an easy solution. I'm sure there's something that I'm missing..
 
You can get the stainless braided lines with a clear cover over them, then just use a few wraps of electrical tape to hold the lines to the gear leg.

Or tie wraps or whatever.

You might check with these guys. http://www.bonacoinc.com/
 
Hydraulics shoppe

They sell the same stuff at much cheaper and you don't have to wait for it if you have one local.

Frank
 
vulnerability when wheel pants are off

I've been thinking about this too.
I'm happy with the aluminum tube running down along the gear leg, but when it bends around in a big loop to connect to the caliper, that big loop is very vulnerable when the wheel pants are off, and probably vulnerable in a really muddy field when mud+grass gets wrapped up inside the wheel pants, flailing around in there.
Has this been a problem? What do people do when they fly with the wheel pants off?

So, I've been thinking about a braided line just for the loop, transitioning to an aluminum elbow fitting on the gear leg or wheel pant mounting plate.
What are others' thoughts about this?
 
scsmith said:
that big loop is very vulnerable when the wheel pants are off, and probably vulnerable in a really muddy field when mud+grass gets wrapped up inside the wheel pants, flailing around in there.
Has this been a problem? What do people do when they fly with the wheel pants off?
Click to expand...

I flew with the pants off for about 50 hours, and I only ran into the big loop once or twice while doing maintenance. Other people ran into it though, even after being cautioned not to. My paint shop did a number on both sides while they were masking, leading me to replace the fittings on the lower ends.

The big loop works fine, and it'll certainly be fine to get the plane flying. I say try it the plans way and then spend the money later if you don't like it.

So, I've been thinking about a braided line just for the loop, transitioning to an aluminum elbow fitting on the gear leg or wheel pant mounting plate.
What are others' thoughts about this?
Click to expand...

Lots of people have done that with success, but to me that just seems like another potential leak point. Also, a -4 fitting at the junction is likely too bulky to fit inside the gear leg fairing. I've seen at least one picture with this problem.

If you're going to go to the trouble to use some flexible hose, my recommendation would be to use all flexible -3 hose. It isn't that much more expensive to run it all the way up the gear leg, and that would eliminate a potential leak point at the junction.
 
Mike S said:
You can get the stainless braided lines with a clear cover over them, then just use a few wraps of electrical tape to hold the lines to the gear leg.

Or tie wraps or whatever.

You might check with these guys. http://www.bonacoinc.com/
Click to expand...

Yeah, I called Brett at Bonaco. His computer was down so he couldn't answer my questions at the time, but he's supposed to call me back.

I was planning on the chafe cover, but that still doesn't prevent the line from touching the landing gear attach bracket. You can see in these pics how the aluminum tubing is bent so it won't rub on anything.

It seems like with this geometry that a flexible line would ride against the landing gear attach bracket on or near the bolt head. Even with a chafe cover, I don't think I'd want that happening for an extended period of time. Eventually something would wear through.

brakeline1-w.jpg


brakeline2-w.jpg
 
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My exact questions this morning

Its funny I just posted this question on the general forum. So does anyone have a picture of a stub flex line to hard line installation?
I know we are using really really soft line but wont this in time, flexing with the gear leg work harden and crack somewhere? I liken it to running a hard line to your engine. And we all know you dont do that. So...i guess it only has to not crack one year at a time though right? since youll have a condition inspection to get through.
 
Geoff thanks

I was actually thinking a flex line of only the loop to the gear leg, not running up like the picture shows. basicly you could take the flex line off without taking the gear leg fairing off.
What would the gotchas be there? is there not room at the wheel pant to gear leg fairing fairing intersection to hide the union?

Geoff your up early this sat morn as well I see, thanks
 
N282RV said:
I was actually thinking a flex line of only the loop to the gear leg, not running up like the picture shows. basicly you could take the flex line off without taking the gear leg fairing off.
What would the gotchas be there? is there not room at the wheel pant to gear leg fairing fairing intersection to hide the union?
Click to expand...

Well, if you're using a flex line down there, you wouldn't need the loop at all. The point of the loop (I think) is strain relief for the semi-rigid aluminum tubing. As long as the caliper has room to move a little, you should be okay. Personally, I think adding another joint in there is adding another potential leak point, but lots of people have done it with success. There is plenty of room in that area to do so.

One thing to think about is that you can't retorque the landing gear bolts (supposed to do it at 10 and 50 hours, and annually thereafter) without disconnecting the brake line at the fuselage bottom because the line goes right over the top of the landing gear bolt. Consequently, when/if you retorque the bolts, you're going to have to remove the fairings and brake lines anyway and then re-bleed the brakes after putting it all back together.

Although at some point I would like flexible lines here, I think for now I'm just going to stick with the factory method. After all, it has worked for hundreds of RVs for thousands of hours. And it's cheap. The only downside is inadvertently kicking the loop when the wheel pants are off.

Speaking of the loop -- I initially made mine way too big. Once you start fitting the wheel pants, you'll see that the loop can't extend very far behind the aft edge of the tire and actually needs to be bent outboard (towards the tire) a little to prevent it from hitting the wheel pant. Once you get the loop down to a reasonable size, the chances of kicking it diminish.
 
It could cause problems...

I know of at least one instance where a builder used flexible lines for the run down his gear legs (6A) and had a bad break resonance problem. It was finally solved by replacing the hoses with solid lines.
Any hose has a small amount of expansion under pressure. If you have a lot of hose, that amount of expansion is multiplied. Even on gear installations that require the use of hose (retractables) they use short links of hose where needed, interconnecting by lengths of solid line.
There is probably differences in types of lines...some may work ok, but considering the cost, it would be best to use a specific line that someone has already used successfully.

I have been building / working on RV's for 20 years...I have found the solid lines to be very reliable if installed properly, and they are lighter and only a fraction of the cost of any hose that you could use.
 
Tubing alloys - what is common...

rvbuilder2002 said:
I know of at least one instance where a builder used flexible lines for the run down his gear legs (6A) and had a bad break resonance problem. It was finally solved by replacing the hoses with solid lines.
Any hose has a small amount of expansion under pressure. If you have a lot of hose, that amount of expansion is multiplied. Even on gear installations that require the use of hose (retractables) they use short links of hose where needed, interconnecting by lengths of solid line.
There is probably differences in types of lines...some may work ok, but considering the cost, it would be best to use a specific line that someone has already used successfully.

I have been building / working on RV's for 20 years...I have found the solid lines to be very reliable if installed properly, and they are lighter and only a fraction of the cost of any hose that you could use.
Click to expand...

Scott,

Vans uses the softer 3003 alum. tubing for brake systems (after he dumped the plastic s&*^...:)...)

Most certified planes seem to use the much stiffer and stronger 5052 tubing, including the new brake lines I just got for my Tiger.

Is there any down side to the much softer tubing, or is it just easier to form and flare?

Do you have any insight into the material selection?
 
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