REFLECTOR: RG System hydraulic oil

[Scott Baker]

Velocity recommends Mil Spec 5606 (red) aviation grade hydraulic fluid for 
RG systems.
SB

----- Original Message ----- 
From: "Tom & Mo Falls" <thefalls at athenet.net>
To: "'Velocity Aircraft Owners and Builders list'" <reflector at tvbf.org>
Sent: Thursday, August 17, 2006 6:06 PM
Subject: Re: REFLECTOR: RG System hydraulic oil


> Al,
>
> I am very interested in your procedure for changing the hydraulic fluid. I
> assume it works for a new un-filled system? I am nearing the point where I
> will fill the system and try it for the first time (oh boy!).
>
> Is ATF the factory recommendation?
>
> Thanks,
> Tom
>
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> Behalf Of Al Gietzen
> Sent: Thursday, August 17, 2006 9:06 AM
> To: 'Velocity Aircraft Owners and Builders list'
> Subject: Re: REFLECTOR: RG System hydraulic oil
>
> Jeff;
>
> When I first filled my gear hydraulics, I used ATF fluid because that is
> what the pump is designed for.  It worked very well.  The principal
> difference for our application between it and the mil spec (is it 5606?) 
> is
> the change of viscosity with temperature.  The mil spec stuff has lower
> viscosity and it stays low all the way to minus numbers like -50 F; which
> planes that fly very high encounter routinely.
>
> Later, after some discussion on this forum, I became concerned about the
> viscosity of ATF at very low temperatures - like -20F  (thinking that some
> day I may be flying in North Dakota in the winter time, silly me).  After
> checking out the data, I concluded that at very low temps the higher
> viscosity could prevent free-fall of the gear in the event of
> electric/hydraulic failure.  I then decided to change the fluid.
>
> I had at least one opinion that the fluids should definitely not be 
> mixed -
> that it would result in seal failure.  Not wanting to chance it, I worked
> out a procedure for changing the fluid (which I will share if any one is
> interested).  The first thing I noticed with the mil spec fluid is a MUCH
> noisier pump.  I suspect it is also more likely to leak as the seals age,
> although mine has now been in for about 8 years and is still working fine.
>
> I hind sight, if I were doing it over, I'd probably leave the ATF in 
> there.
> Definitely the pump likes it better, and I don't think I'm going to want 
> to
> fly this airplane at temps of -20F.
>
> FWIW,
>
> Al
>
> -----Original Message-----
> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
> Behalf Of Jeffrey Clough
> Sent: Wednesday, August 16, 2006 10:37 PM
> To: reflector at awpi.com
> Subject: REFLECTOR: RG System hydraulic oil
>
> I used a local hydraulic shop for some help rebuilding my main gear
> hydraulic cylinder after I dinged up one of the seals and caused it to
> leak. (Caused by a drop of epoxy on the shaft)  I asked them if I could
> purchase some add'l  hydraulic oil and if what they had matched my mil
> spec oil....they said,  'Just use ATF' (Automatic Transmission
> Fluid).......they even said they could be mixed with no
> consequences....has anybody heard of this ...or tried it?
> Jeff Clough   173RG Franklin IVO Clamshell
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