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Cox Engine of The Month
July-2017
Mark Boesen's

Nice original Babe Bee from a Super Cub 105, late fifties.



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Putting my money where my mouth is.

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Putting my money where my mouth is.

Post  batjac on Fri Sep 25, 2015 7:05 am

Well, since I opened my big mouth and suggested it, here’s my unofficial tether car design.  It’s my day off, so I went ahead and started.  Digging in my plywood supplies yielded up a 1/8”x6”x12” piece of ply.  I printed off a picture sort of like what I want and cut it out.  Then I taped it onto the 1/8” ply that I had marked the wheel locations on.  That went over to the scroll saw and the profile got cut out.  My camera is pretty lousy at close up shots, so if anything looks crooked or bent, it’s the crappy lens.





Putting some wheels in place for some perspective.




Once I had the general shape, I drew a base for the car out of more of the 1/8” ply and marked the slots for alignment tabs.  Again back to the scroll saw.





Then a quick test fit of the plate to make sure everything was good.




Then I glued the pieces together with a triangle to ensure alignment.





Next I cut and glued in place an axle bearing tube.




With the axle cut to length and wheels mounted.




Finally for the day, I drilled mounting holes for the drive gear.  I decided first that I would use wheel drive instead of prop drive.  For ease, I went with direct drive.  A tanked Bee didn’t appeal to me, so I figured I’d use the product engine that I used for the Hobbico 1/2A fuel test.  I’ll make up an appropriate tank tomorrow.  To make things symmetrical, I used another product case for the other side.  Besides, if the performance isn’t good I might want to try making a twin engine tether car by putting a piston and cylinder into the idle case.







After assembling everything, I think the wheels I used are just too small.  I picked smaller wheels because I didn’t want to overload the engine when it first starts its run.  Maybe after the first runs I’ll try larger wheels.  Also, I think 12 inches is just a little too long.  I might chop off 1” from the front and another from the back, then squish it down tomorrow.  I think this model is going to be my most expensive 1/2A model to date.  I bought wheels, collars, 5/32" rod, tubing, and landing gear hold-downs today.

The Foot In Mouth Mark
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Re: Putting my money where my mouth is.

Post  crankbndr on Fri Sep 25, 2015 8:02 am

NICE!! I never thought of using a direct drive right off the engine, looks like it will haul butt.
I started on mine also, was thinking about one of these, maybe Art Arfons Green Monster.
I followed these guys in the 60s, couldn't wait for the Mechanics Illustrated to get delivered every month.




So far all I got is an aluminum tube,

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Re: Putting my money where my mouth is.

Post  OVERLORD on Fri Sep 25, 2015 8:07 am

What a coincidence, Since yesterday, I'm walking around with images of the Super Cyclops in my head. I found a 120mm plastic tube.

Crank, are we still concerned about any rules or we do as we like?

Nice start Mark!!
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Re: Putting my money where my mouth is.

Post  crankbndr on Fri Sep 25, 2015 8:21 am

Looks like a "run what ya brung" should be fun!! But this is going to take me months, not days like Mark.
I hope other folks make one too!!
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Re: Putting my money where my mouth is.

Post  Kim on Fri Sep 25, 2015 8:43 am

WAY COOOOOOOOOOOOOOOOOL!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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Re: Putting my money where my mouth is.

Post  1/2A Nut on Fri Sep 25, 2015 8:52 am


Looking real good nice profile idea that folks could adapt.
A spring loaded throttle sleeve could have some advantage during launch instead of releasing at full throttle. The idea as line tension increases the engine opens up all the way. Otherwise you have to toss the car very quickly each time to keep the engine running when the tire hits the pavement producing excessive load which could lead to breaking its con rod over time or wearing into a loose ball socket in short order. Small Cox Logo
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Re: Putting my money where my mouth is.

Post  pkrankow on Fri Sep 25, 2015 9:11 am

1/2A Nut wrote:
Looking real good nice profile idea that folks could adapt.
A spring loaded throttle sleeve could have some advantage during launch instead of releasing at full throttle. The idea as line tension increases the engine opens up all the way. Otherwise you have to toss the car very quickly each time to keep the engine running when the tire hits the pavement producing excessive load which could lead to breaking its con rod over time or wearing into a loose ball socket in short order. Small Cox Logo

Or throwing a tire.

Using a push stick to start is another choice, but you can't adjust anything...

https://www.youtube.com/watch?v=g_VUsp3SWCI

(since I have only seen others run tether cars I don't know much about them)
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Re: Putting my money where my mouth is.

Post  JPvelo on Fri Sep 25, 2015 10:55 am

pkrankow wrote:
1/2A Nut wrote:
Looking real good nice profile idea that folks could adapt.
A spring loaded throttle sleeve could have some advantage during launch instead of releasing at full throttle. The idea as line tension increases the engine opens up all the way. Otherwise you have to toss the car very quickly each time to keep the engine running when the tire hits the pavement producing excessive load which could lead to breaking its con rod over time or wearing into a loose ball socket in short order. Small Cox Logo

Or throwing a tire.  

Using a push stick to start is another choice, but you can't adjust anything...

https://www.youtube.com/watch?v=g_VUsp3SWCI

(since I have only seen others run tether cars I don't know much about them)

Get a 1'x3' piece of sheet metal and apply a liberal amount of talcum powder, you'll get wheel spin that takes load of off the con rod and an awesome burnout effect! lol!
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Re: Putting my money where my mouth is.

Post  getback on Fri Sep 25, 2015 11:57 am

LOOKING GOOD !! Mark you don't waste no time when the erg hits your on it / it should get up and go for sure light weight and direct drive Devil
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Re: Putting my money where my mouth is.

Post  roddie on Fri Sep 25, 2015 1:21 pm

I love it Mark! A great candidate for a simple dyno idea.. I know what you're thinking Rolling Eyes but seriously Laughing all you'd need are 4 wooden spools wide enough for the tires, a couple of rods and a box frame to hold the whole car. It might help you synchronize the needles.
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Re: Putting my money where my mouth is.

Post  JPvelo on Fri Sep 25, 2015 2:24 pm

roddie wrote:I love it Mark! A great candidate for a simple dyno idea.. I know what you're thinking Rolling Eyes but seriously Laughing all you'd need are 4 wooden spools wide enough for the tires, a couple of rods and a box frame to hold the whole car. It might help you synchronize the needles.

That's a great idea. You could mark the spools and use a strobe light for synchronization.

Jim
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Re: Putting my money where my mouth is.

Post  pkrankow on Fri Sep 25, 2015 3:13 pm

You would think that close would be good enough as the two engines would be "connected" via the track, assuming no slip.

I am interested in seeing a twin run.

Phil
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Re: Putting my money where my mouth is.

Post  Marleysky on Fri Sep 25, 2015 4:41 pm

Kim wrote:WAY COOOOOOOOOOOOOOOOOL!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I second Kim's comment. That is just beyond too cool.....WaY Cool is much more descriptive. Just add a little wing for some lift and we'll have a four wheel positraction RTP flying monkey!   W a y. C o o l ...!!  Thanks Mark, I think I've found a place for a couple of engines from my bucket o' engines.   Laughing

BTW: I don't think I've EvEr broke a crank on launching a Cox   049,  car,  corvette, Buick or whatever we were running in circles back in the late 60's early 70's. We wore out tires or crashed the car before the engine broke.   You may not have enough weight to keep the car in contact with the ground anyway.......let's see some videos!

oops, err, the  049 cars were gear driven, the direct drive method WILL cause some undue stress on the engine/crank, upon take-0ff.   Anyway...shoot some video!  Laughing


Last edited by Marleysky on Fri Sep 25, 2015 8:50 pm; edited 1 time in total (Reason for editing : Engineering gearing)
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Re: Putting my money where my mouth is.

Post  batjac on Sun Sep 27, 2015 11:38 pm

Huh...

Well, the more I play with this, more convinced I am that I made it too big for a .049 engine.  I think 8” or 9” is about the right size.    So, I have three choices:  1) Start over from scratch.  2)  Take some off the front and back, leaving the wheels where they are.  3) Chopping off the front, moving the front wheels back, and re-cutting the outline.

I think option 3 is my best choice.  It’s also the most awkward choice.  I'll print out templates at 8", 9", and 10" and see how they look.

I've also just about figured out what I'm going to do for the pivot in the center of the circle.  Now I have to go dig out some old helicopter parts and start assembling that, too.

The Back To The Drawing Board Mark
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Re: Putting my money where my mouth is.

Post  1/2A Nut on Mon Sep 28, 2015 12:15 am

Its a profile wood car weight is just fine its not made out of metal like others. You should just paint it without details and run the sucker to see if the size is okay. If you have an adjustable throttle sleeve you can run at 40% during the initial test and go from there. Eyebrows
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Re: Putting my money where my mouth is.

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