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Remi Guerner
Joined: 14 Dec 2010
Posts: 284
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 Posted: Sat Sep 20, 2014 3:30 am Post subject: Chrome plated brake disk |
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Hi all,
A few years ago, Nigel Graham posted a picture on this forum, which showed a very nicely lightened and chrome plated disc for the Monowheel. See attached.
Nigel, did you have the opportunity to test this disc in actual operation? What about friction ? Wear rate of the pads? Does anyone have operational experience about chrome plated steel discs?
Regards
Remi Guerner
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nigel_graham(at)m-tecque.
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| Posted: Sat Sep 20, 2014 6:27 am Post subject: Chrome plated brake disk |
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Hi Remi,
The short answer is "no". Having done all that work to lighten the wheel
and disc, I moved on to developing my conventional gear, so this ended
up as an "objet d'art".
My original intent was to make the rough-cast agricultural wheel look
more "aviation quality", remove some weight and try to protect against
the horrendous corrosion that the mono wheel gear components tended to
suffer if left un-treated.
My inspiration came from my miss-spent youth customising motorcycles. I
used to drill and chrome those discs and they performed perfectly well
once bedded in (well, a lot better than the cable operated
single-leading-shoe Triumph brakes they replaced).
Over time the chome plate will wear through, but if the wheel and disc
is regularly cleaned and maintained (as I had intended to do) then this
will not affect braking efficiency. Absolute braking efficiency will be
marginally less that a good cast iron disk (the Europa mono is made of
steel), but this is really academic if braking a single wheel on grass.
Accelerated brake pad wear is (or used to be) an issue with the mono's.
People complained of high pad wear which is unusual for a brake with
such a small duty cycle. In extreme cases, the brake fluid could boil
after a long taxi. In rarer cases, the brakes would lock on until they
had cooled. I have a theory as to why this might happen.
There are two possible causes, both related to the calliper. The Europa
Mono calliper was a direct copy of the Cleveland unit, though not as
well made. Neither the alloy of the body or the piston was anodised, so
the piston could corrode and sieze in the bore. Aircraft that were
stored outside or operated off "regularly fertilised" farm strips were
particularly vulnerable.
The other cause is a design fault relating to the piston "O" ring.
Automotive brake calliper "O" rings are square section and are designed
to grip the piston and deform as the brake is applied and the piston
moves. When brake pedal pressure is released, these rings return to
their original shape, dragging the piston back off the disc by a tiny
amount.
The Europa pattern calliper used a round section "O" ring, which does
not grab the piston but simply allow it to slide past. When brake pedal
pressue is released, the piston remains in contact with the disc.
During long taxis, this creates an immense amount of friction, heat and
pad wear. Because the pad is in contact with the hot disc, this heat
sinks back into the calliper. If there is the smallest amount of air in
the calliper, this will expand and increase the brake pressure, locking
it on.
Your next question will be "Where did you source square section "O"
rings", and this is where I have to admit that by then I had moved on to
designing my Conventional gear - so didn't do the research.
Nigel
On 20/09/2014 12:30, Remi Guerner wrote:
| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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Remi Guerner
Joined: 14 Dec 2010
Posts: 284
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| Posted: Sat Sep 20, 2014 8:44 am Post subject: Re: Chrome plated brake disk |
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Thank you Nigel for your answer. I would love to try your special disc. How much do you want for it?
Remi
| | - The Matronics Europa-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
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