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Engine runs backwards

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Engine runs backwards

Post  Cox 049. on Fri Apr 27, 2012 7:08 pm

Hello, I recently got a cox 049. engine. But when I start it, it runs backwards, any tips on what is wrong? or how to fix it?
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Re: Engine runs backwards

Post  Admin on Fri Apr 27, 2012 7:36 pm

Cox engines can run either way. If it is a Tee Dee and it is starting backwards, then it must have a left hand crankshaft. If it is a reed valve bee engine, you can correct this by placing a spring starter on it.

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Re: Engine runs backwards

Post  mitchg95 on Fri Apr 27, 2012 8:16 pm

Admin wrote:Cox engines can run either way. If it is a Tee Dee and it is starting backwards, then it must have a left hand crankshaft. If it is a reed valve bee engine, you can correct this by placing a spring starter on it.

can my medallion .09 do this? im thinking of building a scaled up version of the "boomer" that ivanhoe mentioned a couple of days ago
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Re: Engine runs backwards

Post  microflitedude on Fri Apr 27, 2012 8:26 pm

mitchg95 wrote:
Admin wrote:Cox engines can run either way. If it is a Tee Dee and it is starting backwards, then it must have a left hand crankshaft. If it is a reed valve bee engine, you can correct this by placing a spring starter on it.

can my medallion .09 do this? im thinking of building a scaled up version of the "boomer" that ivanhoe mentioned a couple of days ago

No luck finding a left hand prop?
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Re: Engine runs backwards

Post  RknRusty on Fri Apr 27, 2012 8:43 pm

A Medallion won't run backwards.
For a reedie, the spring is the best. But if you are finger flipping, what happens is, you flip, the piston hits TDC and fires, kicking it off backwards like a bounce. Use the bounce method in the other direction, like you are trying to start it backwards, and it will hopefully bounce off in the correct direction. Hope that works for you. Or, using a chicken stick might help push it through the power stroke and kick it off the right way. You can give it a more powerful flip with the rubber stick.


Last edited by RknRusty on Fri Apr 27, 2012 8:46 pm; edited 1 time in total

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Re: Engine runs backwards

Post  Admin on Fri Apr 27, 2012 8:44 pm

Medallions and TDs are crank timed, they will not run backwards without a LH crank installed. I have had my TD .051 start and run rough for a few seconds backwards but that was because it was way too rich.

Heres a left hand TD .049/.051 crank on eBay: http://www.ebay.com/itm/New-Cox-049-051-Tee-Dee-Left-Hand-Crankshaft-/130582831405?pt=Radio_Control_Parts_Accessories&hash=item1e6757e12d

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Re: Engine runs backwards

Post  mitchg95 on Fri Apr 27, 2012 9:08 pm

microflitedude wrote:
mitchg95 wrote:
Admin wrote:Cox engines can run either way. If it is a Tee Dee and it is starting backwards, then it must have a left hand crankshaft. If it is a reed valve bee engine, you can correct this by placing a spring starter on it.

can my medallion .09 do this? im thinking of building a scaled up version of the "boomer" that ivanhoe mentioned a couple of days ago

No luck finding a left hand prop?

that was someone else looking for one
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Re: Engine runs backwards

Post  microflitedude on Sat Apr 28, 2012 7:01 am

Could you run one in normal rotation using a left hand prop to make a pusher?
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Re: Engine runs backwards

Post  Kim on Sat Apr 28, 2012 7:35 am

mitchg95 wrote:
microflitedude wrote:
mitchg95 wrote:
Admin wrote:Cox engines can run either way. If it is a Tee Dee and it is starting backwards, then it must have a left hand crankshaft. If it is a reed valve bee engine, you can correct this by placing a spring starter on it.

can my medallion .09 do this? im thinking of building a scaled up version of the "boomer" that ivanhoe mentioned a couple of days ago

No luck finding a left hand prop?

that was someone else looking for one

I'm pretty sure I've got some pusher 7-4 wooden props...slated for my Predator/.09. Can't remember where I got them, but can probably part with a couple if you can use them.
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Re: Engine runs backwards

Post  crankbndr on Sat Apr 28, 2012 8:02 am

When starting this old Golden Bee it kept starting backwards, in the video,
you see it didnt start and run forward until I flipped it backward, like Rusty said.

http://www.youtube.com/watch?v=sIEo6xxIVn4
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Re: Engine runs backwards

Post  WingingIt74 on Sat Apr 28, 2012 8:13 am

I've had a TD 051 run backwards, not well but it did run Smile

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Re: Engine runs backwards

Post  nitroairplane on Sat Apr 28, 2012 8:14 am

WingingIt74 wrote:I've had a TD 051 run backwards, not well but it did run Smile
Was it slobbering rich and or flooded on prime?
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Re: Engine runs backwards

Post  WingingIt74 on Sat Apr 28, 2012 8:19 am

something like that

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Re: Engine runs backwards

Post  mitchg95 on Sat Apr 28, 2012 9:57 am

Kim wrote:
mitchg95 wrote:
microflitedude wrote:
mitchg95 wrote:
Admin wrote:Cox engines can run either way. If it is a Tee Dee and it is starting backwards, then it must have a left hand crankshaft. If it is a reed valve bee engine, you can correct this by placing a spring starter on it.

can my medallion .09 do this? im thinking of building a scaled up version of the "boomer" that ivanhoe mentioned a couple of days ago

No luck finding a left hand prop?

that was someone else looking for one

I'm pretty sure I've got some pusher 7-4 wooden props...slated for my Predator/.09. Can't remember where I got them, but can probably part with a couple if you can use them.

pm sent thanks Kim Very Happy
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Re: Engine runs backwards

Post  Ivanhoe on Sat Apr 28, 2012 5:28 pm

microflitedude wrote:Could you run one in normal rotation using a left hand prop to make a pusher?

I see no-one answered you! The answer is yes, you can use any engine as a pusher if you fit a L/H (pusher) prop
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Re: Engine runs backwards

Post  microflitedude on Sat Apr 28, 2012 5:54 pm

Thanks Wilf.

The newer snap starters make it impossible for the engine to run backwards.
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Re: Engine runs backwards

Post  RknRusty on Sat Apr 28, 2012 7:44 pm

I hope the OP got enough info. The thread kind of ran off its topic.

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Re: Engine runs backwards

Post  Ivanhoe on Sun Apr 29, 2012 3:52 am

RknRusty wrote:I hope the OP got enough info. The thread kind of ran off its topic.

Don't they always!
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Re: Engine runs backwards

Post  RknRusty on Sun Apr 29, 2012 10:05 am

Ivanhoe wrote:
RknRusty wrote:I hope the OP got enough info. The thread kind of ran off its topic.

Don't they always!
Yeah, they do, but it's usually with the approval of the OP, who continues to participate. In our tiny community, we're all so familiar with each other, we just bust out into chit-chat at the slightest prompt. But when a new face shows up looking for specific answers, I think it's better to keep on topic.

If a guest or new member pops in and asks a question about cranking his reedie, I think we should refrain from adding a question about our Medallion and continuing on into left hand props. You could always start a thread about your medallion and get the info you want, additionally making it easier for others to search out later on. Usually if I go off topic, it's because I see an opportunity to get a quick semi-related answer to a pressing problem, or to add a humorous quip, then I apologize for doing so and back out. I frequently post a "[/hijack]" to let everyone know not to pursue whatever I injected. Or if one of our topics has been fully hashed and all the info has been covered, it's not a problem either. If you go to a large forum it's certainly bad etiquette to derail a topic.

Just my thoughts. I'll shut up now and finish waking up.
[/hijack]

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Funny story about backwards running engine

Post  Wolf62 on Tue May 29, 2012 4:17 pm

Years ago, in the 1970s I had a Small Cox Logo Babe Bee .049 mounted on a Little Wizzard control line. My engine starter, a friend a few years younger than me, did not realize the engine was running backwards and released the plane. So the plane started backing up and crossing the control line. Out of frustration I jerked the control handle and the prop picked up the line. "Oh Great!" I thought, "Now I've made a mess!" To my suprize Shocked the line hooked the spring starter, stopped the motor and got it running farwards. The line untangled and the plane took off and flew normally Very Happy !
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Re: Engine runs backwards

Post  microflitedude on Tue May 29, 2012 6:07 pm

Now that's something!

Me and Rusty can relate to the reverse launch issue.... Very Happy
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Re: Engine runs backwards

Post  RknRusty on Tue May 29, 2012 8:27 pm

Wolf62 wrote:Years ago, in the 1970s I had a Small Cox Logo Babe Bee .049 mounted on a Little Wizzard control line. My engine starter, a friend a few years younger than me, did not realize the engine was running backwards and released the plane. So the plane started backing up and crossing the control line. Out of frustration I jerked the control handle and the prop picked up the line. "Oh Great!" I thought, "Now I've made a mess!" To my suprize Shocked the line hooked the spring starter, stopped the motor and got it running farwards. The line untangled and the plane took off and flew normally Very Happy !
microflitedude wrote:Now that's something!

Me and Rusty can relate to the reverse launch issue.... Very Happy
Yes we can, I've done it a couple of times. I can not beat the story of hooking the spring, reversing the engine, then taking flight. That is too good to not be on YouTube! Laughing

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Spring NOT a solution to running backwards

Post  brucerli on Tue Apr 09, 2013 6:57 pm

Contrary to what's posted, I've a Cox .049 with a spring starter that will only start forward when it's room temperature. After one flight, it starts backwards, using the spring or flipping (in either direction) every single time. I've given up after 30 attempts. Let it cool off for a few hours, and it starts forward when room temp. Any clues how to work around this issue?
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Re: Engine runs backwards

Post  RknRusty on Tue Apr 09, 2013 7:51 pm

Sounds like you've got an odd one there, Bruce. Try using less of a prime before starting. Sometimes over priming can cause it to kick off backwards. How many head gaskets are in it? try adding one. The rule of thumb with standard Cox heads is one gasket for every 10% of nitromethane starting with 20%; two for 20%, three for 30%, etc. But I sometimes use Three gaskets for 25% too.

Or you could try one of the left hand starter springs. ExModelengines or Cox International probably has one. If you don't see it in their catalog, e-mail and ask. That might be sort of a silly way to solve a problem.

Or even better, buy a snap starter with the cam and spring. It just plain cannot run backwards with that.

http://www.exmodelengines.com/cox-.049-snap-starter-kit.html
http://coxengines.ca/cox-.049-snap-starter-spring-cam-hex-rh.html
You have to have the hexagonal drive plate to use this type.

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Re: Engine runs backwards

Post  WingingIt74 on Tue Apr 09, 2013 8:50 pm

brucerli wrote:Contrary to what's posted, I've a Cox .049 with a spring starter that will only start forward when it's room temperature. After one flight, it starts backwards, using the spring or flipping (in either direction) every single time. I've given up after 30 attempts. Let it cool off for a few hours, and it starts forward when room temp. Any clues how to work around this issue?

A lot of reed type engines will do this. If started with a spring starter, they should only fire one way due to the inertia of the prop in motion. If you hand flip a prop, it can start either way as you do not have the spring inertia behind the prop. What can happen is that once it gets close to TDC it fires... which in turn sends the crank the opposite direction.

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