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02-24-2012, 09:41 AM
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Join Date: Nov 2008
Location: Santa Paula CA
Posts: 183
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Lightening holes in Cleveland brake discs?
Hi all-
Had an EAA tech inspector come over for a midway inspection recently. He is an old-timer, ex-racer, and has built a couple of RV4s. He had put together a list of RV4 lightening mods including drilling holes in the disc brakes as is typically seen on motorbikes, etc. Just curious if anyone has any experience or informed opinion on this.
Eric
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Eric Stewart
=VAF= dues paid 2016
facebook.com/TheSR1Project
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02-24-2012, 10:13 AM
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Join Date: Dec 2006
Location: Coventry. England
Posts: 614
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Done it
Hi
I have done this on my 4 but sorry have no info on how it affects brake wear etc as yet.
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Steve Arnold
England
In completion stage of Loehle P5151
Built and now Flying G.BVLR Vans RV4
Rebuilt G.BDBD Tailwind
Rebuilt G BVTN Kitfox
Built G CDCD RV9A with WAM120
Riveted wings on Glastar G.LEZZ Now (G. SKUA)
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02-24-2012, 02:26 PM
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Join Date: Jun 2007
Location: palm coast fl.
Posts: 945
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Holes
Check out the new Carbon Cub from Cub Crafters , it has holes in the disc . Maybe Randy L can give some input on this.
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02-24-2012, 02:28 PM
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Senior Curmudgeon
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Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 15,408
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Many of the high perf brakes you see are drilled, and or grooved for cooling, and gas dissipation, and not for weight reduction.
http://auto.howstuffworks.com/auto-p...ke-rotors1.htm
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Mike Starkey
VAF 909
Rv-10, N210LM.
Flying as of 12/4/2010 
Phase 1 done, 2/4/2011
Sold after 240+ wonderful hours of flight.
"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."
Last edited by Mike S : 02-24-2012 at 02:53 PM.
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02-24-2012, 02:52 PM
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Join Date: Dec 2006
Location: Portland, OR
Posts: 827
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I think I'd be concerned that if you wore the brake lining down to a rivet head and it caught one of the holes, it could break/rip/tear the pad and then... no brake at all. Food for thought.....
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Long-EZ built 1985 -> Sold 2007
RV-9A; N539RV First Flight: 7/2010
RV-8A N468DL 40 hr Flight Test Program
Building Log: www.mykitlog.com/n539rv
APRS Tracking: aprs.fi/n539rv
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02-24-2012, 02:59 PM
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Join Date: Jan 2005
Location: SC
Posts: 12,887
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I have seen hand drilled rotors come apart under heavy braking. ie: while racing.
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Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
www.repucci.com/bill/baf.html
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02-24-2012, 03:47 PM
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Join Date: Apr 2009
Location: USA
Posts: 1,499
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With pants on I would say that any gain in cooling would be minimal. Then you would need more pressure to be applied to get the same braking action. That would generate more heat. Heat that could not be carried away. If I had rotors in the free airflow then I would go for it.
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Good judgment comes from experience, and a lot of that comes from bad judgment.
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02-24-2012, 03:52 PM
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Join Date: Dec 2011
Location: Meridian ID, Aspen CO, Okemos MI
Posts: 2,641
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saving weight
I have drilled rotors on my car and I think they are pretty good and help in the mountains keeping the brakes cooler. On a plane looking to cut weight, I think I would just not drink a soda or eat a sandwich before the flight.
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02-24-2012, 07:48 PM
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Join Date: Nov 2008
Location: Santa Paula CA
Posts: 183
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Clarification
Hi all, thanks for your comments. To clarify, these holes are for lightening not braking performance. By my calculations (16 evenly spaced 7/16" holes) at 8gm/cm3 density steel weight, savings would be 2 ounces per wheel. Not bad...
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Eric Stewart
=VAF= dues paid 2016
facebook.com/TheSR1Project
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02-24-2012, 08:04 PM
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Join Date: Apr 2009
Location: USA
Posts: 1,499
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You would be removing approx 2.40 sq in of braking surface area X 2 rotors. Aircraft brakes are pushed to the limits. There have been many brake/wheelpant fires to prove it. My rotors gray paint turned brown 1-2" from contact area after 10 hrs and all of my flights to that point were at <50F, no pants and no hard braking. Imagine what it will look like this summer with pants on now.
I would consider cloth seats vs leather or painted interior vs leather/plastic for lightening. That is just me though. That is the nice thing about building your own experimental.
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Good judgment comes from experience, and a lot of that comes from bad judgment.
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