Hand Proping

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Jim Hardin
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Hand Proping

Postby Jim Hardin » Wed Feb 14, 2018 6:41 am

I have asked and webbed it but I always get mixed answers... But I know I can always get good info here 8)

Can you hand prop a Rotex 912 to start it?

Warmi
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Re: Hand Proping

Postby Warmi » Wed Feb 14, 2018 6:44 am

Looks like you can - https://youtu.be/-JUBrHYsh4E
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FastEddieB
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Re: Hand Proping

Postby FastEddieB » Wed Feb 14, 2018 7:34 am

I had always thought it was impossible. That hand propping would not allow the CDI magnets to move past the coils fast enough to generate a spark.

Glad to be shown it’s at least theoretically possible.
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3Dreaming
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Re: Hand Proping

Postby 3Dreaming » Wed Feb 14, 2018 10:32 am

When I went to my first Rotax class this came up. They said that knew of cases of the engine being hand propped. The people who had done it said they would not do it again, except in a life or death situation. Even then they still might not try it again.

A couple things to point out about the video. He states that it is a 912UL, which is the 80 horse version. The 80 HP engine has lower compression and a different gear reduction. Both of these make it a little easier to turn the engine by the propeller compared to the 100 HP version. Another thing is that it looks like he has a Warp Drive propeller, which has more mass than a lot of the other composite propellers in use. The extra mass makes it easier to prop as well.

I have been propping airplanes of all sizes since I was a kid, and I don't think I would try propping a 100 HP Rotax.

3Dreaming
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Re: Hand Proping

Postby 3Dreaming » Wed Feb 14, 2018 2:16 pm

I have one more comment on hand propping a Rotax engine. Other aircraft engine tend to chug to life, taking a little bit of time to spool up. A Rotax will come to RPM much more quickly, just check out the video Warmi posted.
If the throttle happens to be set to a higher RPM the engine will jump to that RMP almost instantly. I know some of you with the soft start function might not realize that they will accelerate that quickly. If you were to hand prop the soft start functions would not come into play.

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WDD
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Re: Hand Proping

Postby WDD » Thu Feb 15, 2018 5:43 pm

FWIW -
Last week I viewed a "everything you wanted to know about a Rotex" youtube video. The presenter was fairly adamant about not hand propping, as the prop speed needs to be higher to start, and it will kick up to an idle that is faster than the larger bore Continentals, etc.

Another comment was that as the electrical system was 12 volt, even a small 12 volt battery in a car or even motorcycle would suffice to jump start it.

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Jim Hardin
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Re: Hand Proping

Postby Jim Hardin » Sat Feb 17, 2018 7:09 am

Thanks for the replies!

I should mention that I have NO intention of hand proping anything anymore :D

I was hoping for a 'why yes I have done that' story or a 1st person, 'I ask Rotax and they said...' but you don't always get what you want.

Did I ever tell you my proping story where I had my student drive me to the ER?

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drseti
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Re: Hand Proping

Postby drseti » Sat Feb 17, 2018 10:10 pm

Did it end with your student high-fouring you?
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FastEddieB
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Re: Hand Proping

Postby FastEddieB » Sun Feb 18, 2018 8:16 am

drseti wrote:Did it end with your student high-fouring you?


Cute.

But actually, it’s how he got the nickname “Lefty”! :shock:
Fast Eddie B.
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rgstubbsjr
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Re: Hand Proping

Postby rgstubbsjr » Sun Feb 18, 2018 10:53 am

I have personally done it. A 100hp with a 3 bladed prop, Maybe 4(?) times.
It's easier to hand prop a 77 year old Cub, and probably safer.

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Jim Hardin
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Re: Hand Proping

Postby Jim Hardin » Sun Feb 18, 2018 11:19 am

FastEddieB wrote:
drseti wrote:Did it end with your student high-fouring you?


Cute.

But actually, it’s how he got the nickname “Lefty”! :shock:


No, just a strain to the rotator cuff. He had a Student Drivers license, so I considered charging him dual. Never driven a clutch before which kept my pain level up. At the ER, older couple backed into us... Quite a day.

Couple of weeks in a sling and I was back to propping that darn O-225 gain :)

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Jim Hardin
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Re: Hand Proping

Postby Jim Hardin » Sun Feb 18, 2018 11:19 am

rgstubbsjr wrote:I have personally done it. A 100hp with a 3 bladed prop, Maybe 4(?) times.
It's easier to hand prop a 77 year old Cub, and probably safer.


Thanks!

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FastEddieB
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Re: Hand Proping

Postby FastEddieB » Sun Feb 18, 2018 12:21 pm

Jim Hardin wrote:
No, just a strain to the rotator cuff.


I see.

1) Was it your right rotator cuff?

2) Can we still call you Lefty?
Fast Eddie B.
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rgstubbsjr
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Re: Hand Proping

Postby rgstubbsjr » Sun Feb 18, 2018 3:11 pm

Where is the like button\smiley face when you need them?


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