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Author Topic: New Retro Discovery engine..  (Read 4067 times)

Online Lauri Malila

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New Retro Discovery engine..
« on: July 01, 2010, 03:46:27 PM »
 Hi.

 Here are some pictures of the new RD .75. It fits in the same mounts as the older .60 and Yuriy has managed to keep the weight allmost identical with the .60 (about 300g without muffler). Muffler is after my lightening about 47g.
 I have spent all night fitting it inside my old Shark. Engine was no problem but it took quite a lot of milling to get the rest inside the nose. Tomorrow I will make the drive-cone to fit the spinner backplate and I can propably test the thing on Saturday. I will let you know what happens..

 Regards, Lauri
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Offline Brett Buck

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Re: New Retro Discovery engine..
« Reply #1 on: July 01, 2010, 06:07:51 PM »
Quote from: Lauri Malila on July 01, 2010, 03:46:27 PM
Here are some pictures of the new RD .75.

  How come it says 78?   Hope we don't get to have that argument again...

    Brett
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Offline Steve Helmick

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Re: New Retro Discovery engine..
« Reply #2 on: July 01, 2010, 06:32:58 PM »
"How come it says 78?   Hope we don't get to have that argument again...

    Brett"


How so, Brett? With the 10g pulltest, (even for AMA) there's no displacement 'fluence on the line sizes, only weight...er, mass. The max displacement allowed is 15cc's or a .91-ish. If Lauri's Yatsenko Shark weighs 64 oz, then it can use .015" cables or .012" solids (for AMA, which of course he doesn't deal with). The thing I don't understand about this (attached chart) is that 64 oz (for example) is listed as the max for .015's, but also the minimum for .018's. Something's wrong there? I don't know where the chart came from, but quite possibly Dave G.  H^^ Steve
« Last Edit: July 01, 2010, 09:19:57 PM by Steve Helmick »
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Re: New Retro Discovery engine..
« Reply #3 on: July 01, 2010, 06:40:12 PM »
Quote from: Brett Buck on July 01, 2010, 06:07:51 PM
 How come it says 78?   Hope we don't get to have that argument again...

 Brett

Brett,

Why does it matter? We are allowed up to a .90. Line size is irrelevant as is only 10 times weight for pull test.

Kim.
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Offline Brett Buck

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Re: New Retro Discovery engine..
« Reply #4 on: July 01, 2010, 10:58:54 PM »
Quote from: Kim Doherty on July 01, 2010, 06:40:12 PM
Brett,

Why does it matter? We are allowed up to a .90. Line size is irrelevant as is only 10 times weight for pull test.

  For the time being.

   Brett
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Offline john e. holliday

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Re: New Retro Discovery engine..
« Reply #5 on: July 02, 2010, 07:55:27 AM »
Maybe he wants to be safe.  I have a couple of engines that are bigger than what is on the case. 
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Offline rustler

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Re: New Retro Discovery engine..
« Reply #6 on: July 02, 2010, 01:49:49 PM »
Have American line size rules changed? I'm under the impression they go by engine size, (hence the anomaly that a 40VF can use a thinner line than e.g. an ST60) and that 76/77 is the break point betweent 18thou and 21thou line requirements? That's why our R&B is a 75. ???
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Offline Brett Buck

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Re: New Retro Discovery engine..
« Reply #7 on: July 02, 2010, 02:45:42 PM »
Quote from: rustler on July 02, 2010, 01:49:49 PM
Have American line size rules changed? I'm under the impression they go by engine size, (hence the anomaly that a 40VF can use a thinner line than e.g. an ST60) and that 76/77 is the break point betweent 18thou and 21thou line requirements? That's why our R&B is a 75. ???

  It's different  now - it goes by weight, not displacement. That started in 2009 and will continue through 2012.

  What I was referring to were the arguments over whether engine X was really a 75, or a 77. An argument easily solved with a bore gauge and a depth micrometer, and not too amenable to internet flamewars.

   People cared because of the line size deal, which is gone, for now at least.

    Brett
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Offline RandySmith

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Re: New Retro Discovery engine..
« Reply #8 on: July 02, 2010, 03:04:28 PM »
""What I was referring to were the arguments over whether engine X was really a 75, or a 77. An argument easily solved with a bore gauge and a depth micrometer, and not too amenable to internet flamewars. ""


There was one motor that if you used the "top of the bore" or the "bottom of the bore" when measurng the tapered sleeve, It would change the line size class...we have no worry of that...for the time being...but who knows what  rule will change  ;D

Randy
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Offline rustler

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Re: New Retro Discovery engine..
« Reply #9 on: July 03, 2010, 03:43:04 PM »
Quote from: RandySmith on July 02, 2010, 03:04:28 PM
There was one motor that if you used the "top of the bore" or the "bottom of the bore" when measurng the tapered sleeve, It would change the line size class...Randy

Another nonsense by the powers that be, and Randy's example proves it! I've never understood why the F.A.I. decided we would measure engine capacity by checking the bore. The capacity of an engine is its swept volume. It is the piston that does the sweeping, and that remains constant whichever part of the bore it is in!  ???
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Offline Brett Buck

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Re: New Retro Discovery engine..
« Reply #10 on: July 03, 2010, 04:30:32 PM »
Quote from: rustler on July 03, 2010, 03:43:04 PM
Another nonsense by the powers that be, and Randy's example proves it! I've never understood why the F.A.I. decided we would measure engine capacity by checking the bore. The capacity of an engine is its swept volume. It is the piston that does the sweeping, and that remains constant whichever part of the bore it is in!  ???

      That was my solution as well, but, when someone wants to make a point - or points - the technical aspects tend to go out the window. Also, to do it you have to disassemble the engine and get the piston out rather than just remove the head.

     Brett
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Offline Norvaldo

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Re: New Retro Discovery engine..
« Reply #11 on: July 03, 2010, 05:09:02 PM »
Hi Lauri.
I was out flying with Clamer today. I heard that the .78 engine ran well.
What is the fuel consumption compared to the .61? And what prop are you using?

Just too bad that a good post with interesting pictures on a new engine is totally derailed into discussion on AMA pull tests and how to measure engine diplacement.
ROJETT and Stalker both have .76 engines. PA have .75 so maybe  mr. Yuriy Yatchenko just decided to beat them with .01 .

Maybe the following quote from Richard Oliver on the ROJETT .76 can put that part of the discussion into perspective:

'After calculating the stroke and bore it came out to .759 ci. At this time I liked the number 77 and labled it such, Dub voted for 76 but I over ruled him for the double 7. New rules came out for line sizes with .76259(?) being the limit for .018 stranded. Looks like Dub Jett got his way after all as I had to change 77 to 76, darnit! '

Norvald





 
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Offline proparc

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Re: New Retro Discovery engine..
« Reply #12 on: July 03, 2010, 08:48:20 PM »
Quote from: Lauri Malila on July 03, 2010, 05:29:36 PM

 
 For next test I will make 21m lines and add 10g weight in tail.

68.8975 feet CL to CL. ::)








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Milton "Proparc" Graham

Offline rustler

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Re: New Retro Discovery engine..
« Reply #13 on: July 04, 2010, 02:56:44 PM »
Quote from: Brett Buck on July 03, 2010, 04:30:32 PM
That was my solution as well, but, when someone wants to make a point - or points - the technical aspects tend to go out the window. Also, to do it you have to disassemble the engine and get the piston out rather than just remove the head. Brett

Fair comment Brett. I guess some speed and T/R folks would not welcome indiscriminate disassembly of their engines.
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Ian Russell.
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Offline john e. holliday

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Re: New Retro Discovery engine..
« Reply #14 on: July 06, 2010, 06:56:12 AM »
To me the Kevlar thread and CA is worse than the epoxy.  When I used to wrap my lines I would leave enough copper wire so that when I got back to the starting point with the second wrap, I could twist the ends together near the eyelet.  They are still flexible.  Wish I could show how I do it as I do a figure eight thru the opening where the eyelet is.  I now do swagging on lines and leadouts.  The little bell at the end of the tubing helps a little.  I have also discovered that handling, connecting and disconnecting is what does the most damage.   H^^

PS:If it wasn't so boring I could spent some time typing how I used to wrap lines and leadouts.  jeh
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