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Post  Cribbs74 Sat May 24, 2014 2:56 pm

I was pondering how to build a fairing/ nacelle around a bee tank or a horse shoe backplate. I realized that a Space Hopper is basically a TD case. So I modded out a Hopper to compete in the fall speed event. It sports a KB crank, #4 P/C, Nelson head and a KK NVA. I also did a little massaging of my own.  Shh 

I bagged all the original parts to re-install upon retirement.

Hot Hopper (finished!) CSxKHX6


Last edited by Cribbs74 on Tue May 27, 2014 9:40 pm; edited 2 times in total
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Post  crankbndr Sat May 24, 2014 3:28 pm

Cool! Have you run it yet? It would be interesting to see what it tachs on 25% and 5/3 prop. Beer Cheers 
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Post  Cribbs74 Sat May 24, 2014 3:33 pm

I'll let you know. I am messing with it now. I'll also try and do video.
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Post  RknRusty Sat May 24, 2014 9:22 pm

Cribbs74 wrote:Hot Hopper (finished!) CSxKHX6

Uh oh!

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Post  Cribbs74 Sat May 24, 2014 9:25 pm

Here is a preliminary video. I wasn't happy with it. This is the 4th KB crank I have messed with and yet again it vibrated like crazy. I am about to give up on those things permanently. Does anyone else have a problem with them?

Here is a video of the run, I have since switched to a Bee crank and the vibes are gone....go figure. That's also why I don't use them in my tach race engines. It sounded too slow to even bother with a tach. I'll take a video of the Bee cranked version for comparison.

Take note of the explosive finish. I didn't want to bother building a new bladder.  Very Happy 

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Post  JPvelo Sat May 24, 2014 9:56 pm

Ron,
I've had five KB cranks. The first two were garbage, vibrated the case oblong in short order. The last three purchased in the last 18 months or so have been great. I have one in my flight time contest engine, over three hours at 21k+ and running smooth. That's the engine that was in my winning speed plane. The corsair also has a kb crank.
For some reason I get better rpms with #1 cylinders on my reedies. It may just be the fit of my particular cylinders.

Jim
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Post  1/2A Nut Sun May 25, 2014 1:46 am

Audio tach had you steady at 17,198 rpm
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Post  RknRusty Sun May 25, 2014 2:14 am

1/2A Nut wrote:Audio tach had you steady at 17,198 rpm
Hey Nut, what are you using for an audio tach, is it freeware?
Rusty

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Post  Cribbs74 Sun May 25, 2014 8:14 am

1/2A Nut wrote:Audio tach had you steady at 17,198 rpm

Neat. Thanks Nut, yeah like I said It sounded slooooow! Audio tach agrees  Very Happy 
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Post  1/2A Nut Sun May 25, 2014 1:48 pm

Yes smart phone app called (RPM Gauge) has an add free version for a few bucks.
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Post  Cribbs74 Sun May 25, 2014 2:30 pm

Must be an Android thing as I can't find an Iphone version.

I was interested even though I have a regular tach. I do all my testing in the shop and I can't use my normal tach inside due to fluorescent lighting. So that means I have to turn off the lights and rig another light source. It's kind of a pain.

Ron
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Post  JPvelo Sun May 25, 2014 5:02 pm

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Post  Cribbs74 Sun May 25, 2014 10:00 pm

Very nice Jim!

I like it. Although I would probably TD that bad boy.

Here is a video from this afternoon. I am getting there, but still not happy yet.

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Post  JPvelo Sun May 25, 2014 10:08 pm

Cribbs74 wrote:Very nice Jim!

I like it. Although I would probably TD that bad boy.
I have a 1/2a speed pan I need to do something with. How about the pitch in that prop!

Jim
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Post  Cribbs74 Sun May 25, 2014 10:14 pm

Yeah, looks like a 7 or 8 pitch. RPM must have suffered under that load. Buy it Jim!
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Post  JPvelo Sun May 25, 2014 10:23 pm

Cribbs74 wrote:Yeah, looks like a 7 or 8 pitch. RPM must have suffered under that load. Buy it Jim!
Nah, I have the pan and plans to make my own.
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Post  Cribbs74 Sun May 25, 2014 10:27 pm

Yeah.... But it has a space hopper in it.

I am beginning to wonder if the intake diameter is limiting me. I am not going to drill it and find out.
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Post  JPvelo Sun May 25, 2014 10:38 pm

Cribbs74 wrote:Yeah.... But it has a space hopper in it.

I am beginning to wonder if the intake diameter is limiting me. I am not going to drill it and find out.
Did you remove  the screen?
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Post  Cribbs74 Sun May 25, 2014 10:43 pm

No I did not. I am not wanting to do anything irreversible. I'll take a peek and see if it can be done.

Another option would be to close up the intake on a TD and see how it does with the SH backplate.



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Post  JPvelo Mon May 26, 2014 9:18 am

Cribbs74 wrote:
Another option would be to close up the intake on a TD and see how it does with the SH backplate.

Ron,
To eligible for Reed Speed it needs to be reed valve case, no modded TDs'.

Jim
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Post  Cribbs74 Mon May 26, 2014 10:04 am

Thanks...... Devil 


Guess I will keep trying.
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Post  1/2A Nut Mon May 26, 2014 1:37 pm

 Small Cox Logo Best was 17.684 rpm.
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Post  Cribbs74 Mon May 26, 2014 2:57 pm

Well, it's an improvement in the right direction anyway...... lol! 

Thanks Nut.
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Post  Cribbs74 Mon May 26, 2014 8:33 pm

Ok,

I am satisfied with it now. I got it to turn over 19K on a Cox 5x3.

With the APC 4.75x4 I should be in the 20K range and competitive. I didn't have one on hand to try.

Here is a video of the results. I apologize for the bad camera work I kept setting the phone down to work the needle. I also had to keep moving the tach around to catch the light for the tach to read right...

All I did is use a nut without the screen and remove a head shim.






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Post  JPvelo Mon May 26, 2014 9:08 pm

Nice! What % nitro?
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