[Stewie]

Hi all-
I am replacing the plastic brake line in my -4 with -3 braided hose from Bonaco. Original plans show the plastic as a single line from master cylinder all the way down to the caliper. In perusing the forums for info on hoses, all of the pics I have seen show a cockpit line terminating at a bulkhead fitting in the firewall/fuse, then another line continuing from there to the wheel. Just curious if there is a reason why a single line routed through a bushing/grommet is necessarily a bad idea.
Any thoughts would be appreciated.
Thanks,
Eric

 

[Vac]

Single lines work fine

Hi Eric,

We have single Bonaco lines on both sides of our -4. They run via grommets in the cowl cheeks. Less fittings to leak. Be sure to adequately support them along the run to prevent chaffing.

Cheers,

Vac

 

[TS Flightlines]

Eric, if for other reason, we crimp our hose ends on the hoses. Because of that, you'd need a 9/16 hole in the firewall to allow the hose end B nuts to clear. Thats a pretty good sized hole to seal up.
I have seen guys use braided teflon hose with reusable hose ends and run a small grommetted hole in the firewall. They then attached their hose end. I'm ok with the hose end part, but my crazy about the grommetted hole in the firewall.
(Those that I have done, we've changed to bulkhead fittings).
Tom

 

[Stewie]

Thanks

Mike and Tom-
Thanks for both your replies. Tom, the RV4 lines exit through the fuse side inside the cheek extensions so no firewall issue there - I did figure though that one reason people use bulkhead fittings is due to the rather large hole required to pass a b-nut through. Anyway, firewall point well taken for future builds. I will go with a single line, as Mike said less possibilities for leakage and probably a bit lighter. Will be sure to provide anti-chaffe and good support.
Thanks!
Eric

 

[Vac]

Strain Loop

Eric,

I forgot to mention it, but even though the new lines are flexible, don't forget about the strain loop at the wheel when you take your measurements. There is plenty of room for the loop, even with "old style" two-piece leg fairings and Van's original wheel pant design. The loop/tubing run is shown on the drawings.

There is quite a bit of movement (flex) in the Whitman style gear during taxi, takeoff and landing--even more so on unpaved surfaces.

Self-amalgamating silicone tape is a great way to attach the lines to the gear legs. Wrap the lines first or use nylon flex wrap to prevent the braid from chaffing.

If you're replacing old lines, it's a good time to consider switching to high temp hydraulic fluid and Viton o-rings in your calipers as well. Lots of good/recent discussion on this topic.

If you're already way ahead of me, ignore the unsolicited advice!

Cheers,

Vac