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Cox Engine of The Month
November-2017
MauricioB's

"Cox Tee Dee .010"



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Cox Engine Forum Speed Contest 2018!!!

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Re: Cox Engine Forum Speed Contest 2018!!!

Post  pkrankow on Sat Oct 28, 2017 9:01 pm

Ken Cook wrote:         Jim, one thing I find that happens when something like this is brought to the table is that your faced with many why can't we do this questions. I in no means am suggesting any alteration of the rules. I'm just throwing this out there because I already own several of these models which don't exactly fit the criteria of the rules in regards to the wheel limit. Most speed contests suggest the 2 wheel rule. However, only a limited event demands the 2 wheel rule. In most of the racing events I have participated in, the rules state that a single wheel gear must be a of a certain size. Seeing that the majority of my planes are one wheel, the only advantage to this is less drag and that's marginal at best. So I'm asking, is a one wheel gear acceptable? If not, completely understood. Ken

Just use a pin and put a wheel on the wingtip.
lol!
Phil
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Re: Cox Engine Forum Speed Contest 2018!!!

Post  JPvelo on Sun Oct 29, 2017 6:25 am

Ken Cook wrote:         Jim, one thing I find that happens when something like this is brought to the table is that your faced with many why can't we do this questions. I in no means am suggesting any alteration of the rules. I'm just throwing this out there because I already own several of these models which don't exactly fit the criteria of the rules in regards to the wheel limit. Most speed contests suggest the 2 wheel rule. However, only a limited event demands the 2 wheel rule. In most of the racing events I have participated in, the rules state that a single wheel gear must be a of a certain size. Seeing that the majority of my planes are one wheel, the only advantage to this is less drag and that's marginal at best. So I'm asking, is a one wheel gear acceptable? If not, completely understood. Ken

Ken,

I'm going to say no because I don't want to open the door to making changes to a very simple set of rules when there is over a year to build or modify a model.
I hope that didn't come across as snarky.

Jim
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Re: Cox Engine Forum Speed Contest 2018!!!

Post  Ken Cook on Sun Oct 29, 2017 6:40 am

Not at all. I have no interests in building more as space is at a minimum now. I have refined what I have currently and the only places I have to fly this style of plane is limited to twice a year. There's currently one with dual gear not setup for suction and I will see if it's possibly doable for a tank.
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Tee33 Dee

Post  roddie on Sun Oct 29, 2017 6:57 pm

Trying to figure out how I'm going to install a trike-gear on my T33. Huh... Huh... Huh... I'm pretty much set on .062" music-wire for the mains.

A 3-view that I've been working from..



I considered an inverted "V" for the mains.. because I ran the engine-mount beams well rearward.. and could tie-into the lower beam with steel L/G straps located midway to the wing-chord.  



I'm not sold on that arrangement though. My Rare Bear's "mains" consisted of two separate struts mounted under its' sheet-wing. That wing was built with a hardwood "strip-spar" for the gear-blocks to tie-into.





The T33's wing doesn't have that hardwood strip-spar.. because the model was originally designed to launch "gearless" from a dolly. I still like the idea of two separate wing-mounted struts though. Not too far apart.. maybe 8".

The nose-gear/strut will also be .062" music-wire which will tie-into the lower engine-mount beam.. and be raked-back a few degrees from vertical.. to hopefully provide some shock-absorbing when the model comes down when landing.. or otherwise..

The wheels are surplus-stock.. and are the same as the ones used on the Rare-Bear. Their hubs will be bushed to fit the .062" diameter music-wire axles.

I made these wheels on a CNC router.. and have a LOT of spares. With an O-ring "tire".. they measure 1.100" diameter and .180" in thickness. I'd be more than willing to share what I have, with fellow CEF members if they desire thin-streamlined wheels for their entry. PM me.
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Re: Cox Engine Forum Speed Contest 2018!!!

Post  JPvelo on Tue Oct 31, 2017 2:24 pm

Ken Cook wrote:         Not at all. I have no interests in building more as space is at a minimum now.

I understand that, I am currently in the process of selling off everything non cox bigger than 1/2a size.
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Re: Cox Engine Forum Speed Contest 2018!!!

Post  JPvelo on Tue Oct 31, 2017 7:48 pm

Yep, that's a model airplane.
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Re: Cox Engine Forum Speed Contest 2018!!!

Post  roddie on Wed Nov 01, 2017 9:43 pm

JPvelo wrote:Yep, that's a model airplane.

Yep.. it sure is! You still plan on flying it CW rotation Jim? I'm Popcorn  anxious to see how you set up the controls.. landing-gear and the fuel-delivery! This should be fun! I hope that we gain more participants! We should; given the amount of time allotted to build a model.. along with flight-testing. Who hasn't wanted to build a "hot-rod" airplane for one of their little Cox engines?
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landing-gear retro-fit

Post  roddie on Fri Nov 03, 2017 6:55 pm

I spent a little time trying to fit landing gear to my T33 Shooting Star this afternoon. Tedious......... I'd NEVER built a "trike-gear".. This design will be stout; constructed completely of .062" piano-wire.. and 1.0" diameter wheels

The "mains".. mounted mid wing-chord.. an inverted "V" with a 6" track with struts raked slightly rearward.










The nose-gear...  I made a sheet-brass spreader-plate for tying the gear-wire into the lower-engine mount. It's strut is also raked slightly rearward..






the "stance"... less wheels..




This was a tricky thing for me. I hadn't made provisions for any landing-gear. This model was to be launched from a "dolly".. which had been previously built. It's a "trike" now........  Laughing and I hope that she rolls-out on track. I have a few degrees of starboard-castor bent into the nose-gear's axle.

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Re: Cox Engine Forum Speed Contest 2018!!!

Post  RknRusty on Fri Nov 03, 2017 7:52 pm

That looks like a nice job, Roddie. How do you know the fore-aft position? Is there a rule of thumb for model planes' trike gear as with conventional tail-dragger gear? I was just talking with a friend yesterday about his trike Pathfinder and he was frustrated having a hard time with rolling takeoffs.

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Re: Cox Engine Forum Speed Contest 2018!!!

Post  batjac on Fri Nov 03, 2017 11:19 pm

RknRusty wrote:That looks like a nice job, Roddie. How do you know the fore-aft position? Is there a rule of thumb for model planes' trike gear as with conventional tail-dragger gear? I was just talking with a friend yesterday about his trike Pathfinder and he was frustrated having a hard time with rolling takeoffs.

An old rule of thumb I learned lo 'bout 30 years ago is 15%.  For a conventional gear plane, the main wheels should be 15% of wing chord ahead of the C.G. point.  For a tricycle gear, the main wheels should be 15% of chord aft of the C.G.  This makes for easy rotation.  It's worked fine for me as a general rule.  But then, I never fly a plane long enough to want to fine tune the landing gear position.  I know some people put the mains closer to the cc.g. for a tricycle gear to make it rotate quicker, but I figure they drag their tail more, also.

The Conventional Mark
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Re: Cox Engine Forum Speed Contest 2018!!!

Post  batjac on Fri Nov 03, 2017 11:20 pm

Nice looking plane, Roddie. Can't wait to see it tricked out with paint and details. Are you gonna fly it with the Medallion for the contest?

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Re: Cox Engine Forum Speed Contest 2018!!!

Post  JPvelo on Sat Nov 04, 2017 1:42 pm

Nice work Roddie!
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Re: Cox Engine Forum Speed Contest 2018!!!

Post  roddie on Sat Nov 04, 2017 6:14 pm

RknRusty wrote:That looks like a nice job, Roddie. How do you know the fore-aft position? Is there a rule of thumb for model planes' trike gear as with conventional tail-dragger gear? I was just talking with a friend yesterday about his trike Pathfinder and he was frustrated having a hard time with rolling takeoffs.

I don't know Rusty..... lol! I'm fairly certain that the model would have been excessively nose-heavy prior to the gear installation.. so this gear retro-fit is probably in my favor. Some added functional-weight via the mains-position at mid-chord; I thought was a safe bet. The few degrees of "rearward-cant" on all three struts I figured might provide for a less "bouncy" roll-out.. as well as some shock-absorbing when the model falls out of the sky when the engine quits.. Laughing

I made the struts long initially. so I could trim them shorter. I trimmed 1" off the nose-gear.. and 1/2" off each main-strut..



Here's how she sits now; "less" her 1" dia. wheels..



2.5" above the deck.. plus 1/2" with wheels. I hope that the 1/2" increase in height doesn't make it look fugly.. but we'll need ground-clearance for a 5" max-dia. propeller. The nose gear's wheel I've decided to consist of a stronger material than the lightweight main-wheels.

I also bit the bullet today.. and bought a Dodge Viper RT/10..



Laughing It's probably the closest I'll ever get to one.. $.94 at my local Walmart.. Smile
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Re: Cox Engine Forum Speed Contest 2018!!!

Post  roddie on Sat Nov 04, 2017 6:37 pm

batjac wrote:Nice looking plane, Roddie.  Can't wait to see it tricked out with paint and details.  Are you gonna fly it with the Medallion for the contest?

The Inquisitive Mark

Thank you Mark!! That engine is a Tee Dee .051 that I fitted for the photos. You can see it more clearly in my last post. A Tee Dee .049 will be the engine of choice.. and is packed-away in a zip-seal bag because I borrowed its glow-head for a reed-valve engine that I entered into this year's CEF tach-race unlimited-class.

For the 2015 Speed-Contest, I bought some "Krylon" Cover-Maxx paint; aerosol "true blue" base-color and a pint-can of "sun yellow" for the trim. I'm hoping to accurately represent a "Blue Angels" color-scheme.



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Re: Cox Engine Forum Speed Contest 2018!!!

Post  roddie on Sat Nov 04, 2017 7:08 pm

JPvelo wrote:Nice work Roddie!

Thanks so much Jim! "You've " been the catalyst since this whole thing started four years ago. It gave me a focus back then.. when a lot of my life was out of focus. I'm thankful for that Jim. The very "nature" of this contest is creativity. That's what I love the most about it! One-off models that there are no kits for. Each one; a unique creation.. unlike anyone else's. We all hope that we can control them when they're unleashed.. biting into the air with fury!
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Re: Cox Engine Forum Speed Contest 2018!!!

Post  roddie on Sat Nov 04, 2017 7:57 pm

batjac wrote:
RknRusty wrote:That looks like a nice job, Roddie. How do you know the fore-aft position? Is there a rule of thumb for model planes' trike gear as with conventional tail-dragger gear? I was just talking with a friend yesterday about his trike Pathfinder and he was frustrated having a hard time with rolling takeoffs.

An old rule of thumb I learned lo 'bout 30 years ago is 15%.  For a conventional gear plane, the main wheels should be 15% of wing chord ahead of the C.G. point.  For a tricycle gear, the main wheels should be 15% of chord aft of the C.G.  This makes for easy rotation.  It's worked fine for me as a general rule.  But then, I never fly a plane long enough to want to fine tune the landing gear position.  I know some people put the mains closer to the cc.g. for a tricycle gear to make it rotate quicker, but I figure they drag their tail more, also.

The Conventional Mark

I don't really know what to expect from this trike-gear. Huh... It's my first model-airplane so equipped. I basically "winged-it" (pardon the pun..) with the orientation/placement. This model-subject being a "jet" is way outside the box for a front-engine propeller-driven variant. Its "sheet-wing" is small and offers zero-lift.. Laughing Its proportions are eye-ball scale.. so as to "look" the part. Whether it will fly and be controllable is anyone's guess. The wingspan is 15.0" with a 4" root-chord and 2" tip-chord.. for a total of 45 square-inches.

The model sits with a slightly positive angle of attack. It has very small (scale) tail-feathers. The stab./elevator span is 5" and the elev. area is only 2.5". Control-throws will be tight.. maybe 10-15 degrees. I don't dare provide more deflection than that. What "will suck".. is if I need to have "more" control to avert a crash.
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Re: Cox Engine Forum Speed Contest 2018!!!

Post  Oldenginerod on Sun Nov 05, 2017 1:56 am

I might have missed something here as I haven't been following the thread so closely, but with Roddie building a "trike" I do recall that the orignal rules stated "2 wheels". Is a third wheel allowed, like on Roddie's model? I remember some discussion about single gear models not being allowed. What's the latest?
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Re: Cox Engine Forum Speed Contest 2018!!!

Post  JPvelo on Sun Nov 05, 2017 5:27 am

Oldenginerod wrote:I might have missed something here as I haven't been following the thread so closely, but with Roddie building a "trike" I do recall that the orignal rules stated "2 wheels".  Is a third wheel allowed, like on Roddie's model?  I remember some discussion about single gear models not being allowed.  What's the latest?

I just modified the rules to read "landing gear with a minimum of 2 wheels". That was always the original intent, I should have been more clear from the beginning.
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T33 wheels

Post  roddie on Mon Nov 06, 2017 1:42 pm

WOW!.. this thread has 4K+ views in less than 30 days.. Damn!

I've been trying different wheels on this jet. These are Perfect-brand 1.375" dia. streamlined mains.. and one of my homemade wheels for the nose-gear. I may swap-out wheel "types" later for balance.. but the 1.375" diameter seems to look better than anything smaller or larger.






With these wheels; the airplane currently balances at the extreme-front of the wing-tip pods, without a tank or fuel payload. A premature estimation; having no paint or control-linkage.. but I prefer to check balance a few times throughout the build.. in an effort to avoid having to add non-functional weight when the model is finished. A piano-wire vs. carbon-fiber pushrod can be all it takes to trim the CG of a model this tiny.. as long as it's in the ballpark at finish-time.

The model sits much higher than scale for propeller-clearance.. and a "Kress-Midwest" ducted-fan unit would be trick.. Cool but let's be real... Laughing

I'm considering adding a "KFm" (Kline-Fogelman) stepped-airfoil leading-edge for my 1/8" sheet-wing, to hopefully gain some stability. Something in the order of the KFm-10 shown in the image below. A symmetrical foil.. having a L/E made from 1/4" stock with trailing graduated-strips of 1/16", 1/32" and 1/64" wood.



A .015" dia. piano-wire "tail-skid" with an "eye" on its end will serve as a stooge-pin launch-point.

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Prowler

Post  roddie on Thu Nov 09, 2017 9:17 am

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Re: Cox Engine Forum Speed Contest 2018!!!

Post  JPvelo on Thu Nov 09, 2017 9:47 am

This things getting close.



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Re: Cox Engine Forum Speed Contest 2018!!!

Post  roddie on Thu Nov 09, 2017 10:10 am

That is WICKED Jim!!!!!!!!! Thumbs Up Popcorn
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Re: Cox Engine Forum Speed Contest 2018!!!

Post  GWILLIEFOX on Fri Nov 10, 2017 7:31 am

Are the final rules listed all together in one place?
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Re: Cox Engine Forum Speed Contest 2018!!!

Post  JPvelo on Fri Nov 10, 2017 8:49 am

GWILLIEFOX wrote:Are the final rules listed all together in one place?

The rules posted at the beginning of this thread are the final complete rules.

Jim
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Flying blind...

Post  roddie on Fri Nov 10, 2017 3:14 pm

I figured that there's enough time to design an "additional" model for this contest. The post-title has meaning.



That's a wooden window-blind. I found a stack of them (10) in an old abandoned garage a few years ago.. and being "me".. thought about an aero-modeling application for them.. and gathered them up.

They measure .130" thick x 2.375" wide x 24" long. What's unique about these.. is that you don't commonly find hardwood cut as thin as this. The pieces are perfectly straight and warp-free.



The blinds "are" wood.. possibly basswood.. but I'm not sure.



My "challenge".. is to use one piece of this blind, to build "most" parts of a Speed model for this contest. It will be a "profile" model to keep it simple. I have 57 sq. in. to work with..
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Re: Cox Engine Forum Speed Contest 2018!!!

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