REFLECTOR: Main Gear Brake Heat Shield
Scott Derrick
scott at tnstaafl.net
Wed Sep 23 17:45:53 CDT 2009
You know, its so much easier on everybody if you reply at the top of the
post. Remove detritus as you go along if it doesn't support your reply.
Don Johnston wrote:
> Jon,
>
> It's sandwiched between the axle and the gear leg.
>
> http://www.velocity-xl.com/pictures/2009/IMG_8828.JPG
> http://www.velocity-xl.com/pictures/2009/IMG_8848.JPG
>
> -Don
>
>
> Date: Wed, 23 Sep 2009 09:44:29 -0500
> From: "Bachman, Jonathan" <Jonathan.Bachman at mtsi-va.com>
> Subject: Re: REFLECTOR: Main Gear Brake Heat Shield
> To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
> Message-ID:Content-Type: text/plain; charset="us-ascii"
>
> Don,
>
>
>
> How did you install the shield? Did you make axle bolt holes and
> sandwich it between the axle and the leg? Last time I looked at the
> leg, I noticed that the leg hangs down below the axle and is exposed to
> radiated heat from the disk too. Does the shield need to protect that?
>
>
>
> Jon
>
>
>
> ________________________________
>
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> Behalf Of Don Johnston
> Sent: Tuesday, September 22, 2009 3:42 PM
> To: reflector at tvbf.org
> Subject: REFLECTOR: Main Gear Brake Heat Shield
>
>
>
> Jon,
>
>
>
> I used a high-temp phelolic from McMaster-Carr (P/N 8641K122). The
> minimum size is 12"x12" but you only need half that.
>
>
>
> I still have the leftover from my sheet if you're interested.
>
>
>
> -Don
>
>
>
>
>
>
>
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
>
> Behalf Of Bachman, Jonathan
>
> Sent: Tuesday, September 22, 2009 11:05 AM
>
> To: Velocity Aircraft Owners and Builders list
>
> Subject: REFLECTOR: Main Gear Brake Heat Sheild
>
>
>
> What is the best way to add some protection to the main gear legs to
>
> prevent overheating from the brake disks after heavy usage? My plane
>
> has nothing, no shield, no wrap, and no AL tape. I've read about the
>
> problems that overheating the gear leg can cause and I don't want to
>
> have to go there.
>
>
>
> Thanks
>
>
>
> Jon Bachman
>
>
>
> N956DR
>
>
>
> Std RG
>
>
>
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> ------------------------------
>
> Message: 5
> Date: Wed, 23 Sep 2009 09:06:02 -0800
> From: "Al Gietzen" <ALVentures at cox.net>
> Subject: Re: REFLECTOR: Brake heating question
> To: "'Velocity Aircraft Owners and Builders list'"
> <reflector at tvbf.org>
> Message-ID: <D37D285DD013411882819C411BBBF171 at BigAl>
> Content-Type: text/plain; charset="us-ascii"
>
> Drawing on my past experience in heat transfer analysis; I concluded that
> the dominant heat transfer mode, for the RG, with the Matco brakes, is
> radiant heat from the rotor to the leg. I'm sure there is also transfer
> through the axle; however, that conductive transfer path from the rotor,
> through the rim, and through the bearings to the axle is rather torturous,
> so we'd expect that the temp drop from rotor to leg would likely be large.
> Probably more likely to damage the tire at the bead before damaging the gear
> leg.
>
>
>
> Because of the air freely moving between the rotor and the leg on the RG,
> conduction through the air to the leg is likely small. The best way to stop
> radiant transfer is with a reflective baffle, with air space behind. A
> reflective wrap on the leg is good, but the material is a conductive path
> from the reflective surface, which will get hot.
>
>
>
> With wheel pants the story is somewhat different because of the trapped air;
> but I'd say a reflective baffle is still important, as are air vents in the
> pants.
>
>
>
> We have no experimental data on the heat flow paths, so my analysis could be
> wrong.
>
>
>
> OTOH; I've done 285 landings with my plane (SE RG), on various runway
> lengths, and with the associated taxi maneuvering, without a problem. My SS
> baffle (I think it is .016") attaches between the axle and leg, with no
> other insulating material between.
>
>
>
> FWIW,
>
>
>
> Al
>
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> Behalf Of Scott Derrick
> Sent: Wednesday, September 23, 2009 6:28 AM
> To: Velocity Aircraft Owners and Builders list
> Subject: Re: REFLECTOR: Brake heating question
>
>
>
> My question would be, what kind of heating are people talking about?
>
>
>
> 1.) Heat build up inside wheel pants?
>
>
>
> 2.) Radiant heat from the disk transferring through the air onto the
>
> exposed gear leg?
>
>
>
> 3.) Heat transfered from the disk, to the axle and then through the axle
>
> into the gear leg?
>
>
>
> 1 & 2 seem to be the most likely and require different solutions.
>
>
>
> I'm having a hard time seeing how #3 really happens. Seems like that
>
> amount of heat would really fry the bearings also.
>
>
>
> Scott
>
>
>
> David Ullman wrote:
>
>
>> I frequently read on this site about brake heating problems. Is this just
>>
>
>
>> with the larger craft? I have an SE. Should I be installing a heat shield
>>
>
>
>> while I am building it?
>>
>
>
>
>
>> David G. Ullman
>>
>
>
>> Robust Decisions
>>
>
>
>> ullman at robustdecisions.com
>>
>
>
>> 541-754-3609
>>
>
>
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