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Post  roddie Sun May 19, 2024 9:58 pm

Sort of a break-in run.. but curious to know RPM's when leaning-out.. thanks  Smile




Here's a 2nd run that's purely for your entertainment pleasure.. Don't worry.. the engine is ok; contrary to my comments at the end of the vid.



Last edited by roddie on Mon May 20, 2024 6:19 pm; edited 1 time in total
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Post  F4D Phantom II Mon May 20, 2024 3:06 am

Hello roddie
                         I picked up 18080 rpm at one point on my audio tach on the first video.
                 
                                                                                 juan
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Post  roddie Mon May 20, 2024 3:41 am

F4D Phantom II wrote:Hello roddie
                         I picked up 18080 rpm at one point on my audio tach on the first video.
                 
                                                                                 juan

VERY COOL!!! Cool Cool Cool Thank You!!!
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Post  944_Jim Mon May 20, 2024 4:53 am

Hi Roddie,

I still have a couple of those 1/2/A Dubro clips...do you need one? They work well (put on/take off easier) if you assemble with a long 4-40 screw and nut. See how Juan did his in the Dubro clips thread (Best Norvel Starter Clip thread from 4 years ago, last update last month).


I have an Android phone. I use an audio-tach app on it. It runs pretty close to my other tach...one of those cheap hold it near the prop tachs.

Hmmm...maybe I'll load the tach app on my obsolete Moto G5. This way I don't have to work so hard to clean my latest phone.

I suspect there are similar programs for iThingies.

I may try running the audio tach against a PC playback of your videos. It would be cool to see if that works!

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Post  1/2A Nut Mon May 20, 2024 6:41 am

I get 26,889 rpm @ 52 sec in on the 1st. vid.
24,790 on the 2nd vid.

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Post  balogh Mon May 20, 2024 2:04 pm

audio-tach anyone? Screen55

Roddie, this was shat I audiotached just before the engine suddenly stopped. I suspect in this 2nd vid the crankpin may have been already bent, hence the lower speeds than in the 1st.

At such a speed especially  later, post heyday reedies with slit exhaust  i.e 90's cylinders may have their crankpin broken. This will most likely damage the backplate too like breaking the rim that holds the circlip...been there, seen that, done that...my exceptionally lasting old stock red postage stamp  backplate reedies survived even 28k+ speed on long runs in my Quickie100 ( see my video with such post title) but even some of those ended up with broken pins and damaged backplates..I suggest you use the KB crank, even if their fit in the case is very loose and the radial play is embarrassingly large...I wish Bernie and Matt changed the blueprint for the aftermarket KB cranks, that would help sustain reedie speeds 25+k and higher...I personally do not like the aftermarket KB cranks because of their very sloppy fit.

Contrary to the common belief that loose fit KB shafts help boost engine speed, the radially unsupported shaft will wobble even with the best balanced prop, due to the unbalanced radial forces of the piston rod acting through the pin..a few years back Matt replied to me saying once the aftermarket KB shafts he then had on stock all sold, he will reorder a new run with tighter fit. I am not sure if the currently sold KB shafts have tighter fit, anyway, a properly fit KB shaft could well serve reedie performance experiment with unloaded shafts (e.g. only a  flywheel) like yours, Roddie.
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Post  roddie Mon May 20, 2024 4:43 pm

944_Jim wrote:Hi Roddie,

I still have a couple of those 1/2/A Dubro clips...do you need one? They work well (put on/take off easier) if you assemble with a long 4-40 screw and nut. See how Juan did his in the Dubro clips thread (Best Norvel Starter Clip thread from 4 years ago, last update last month).


Jim! Where'd you get all them clips??? lol!     I actually have one N.I.P.... but THANKS for offering!

audio-tach anyone? Cef_9410

I see now how Juan did his. I have some 4-40 X 1"L. cap-screws and a 4-40 tap to do the same mod. Thanks for that info too!!!

audio-tach anyone? Cef_ju10

audio-tach anyone? Cef_ju11
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Post  roddie Mon May 20, 2024 4:49 pm

1/2A Nut wrote:I get 26,889 rpm @ 52 sec in on the 1st. vid.
24,790 on the 2nd vid.

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Thanks very much Brad!!! Between yours and Andras' readings; looks like the avg. was around 24K. Thumbs Up Babe Bee .049
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Post  getback Mon May 20, 2024 4:53 pm

roddie did you find the crank pin broken in the engine ? Here is the discussion about the KB > https://www.coxengineforum.com/t10733-killer-bee-crankshaft?highlight=killer+bee
Is that a car engine case and crank ?
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Post  roddie Mon May 20, 2024 5:38 pm

balogh wrote:

Roddie, this was what I audio-tached just before the engine suddenly stopped. I suspect in this 2nd vid the crankpin may have been already bent, hence the lower speeds than in the 1st.

At such a speed especially  later, post heyday reedies with slit exhaust  i.e 90's cylinders may have their crankpin broken. This will most likely damage the backplate too like breaking the rim that holds the circlip...been there, seen that, done that...my exceptionally lasting old stock red postage stamp  backplate reedies survived even 28k+ speed on long runs in my Quickie100 ( see my video with such post title) but even some of those ended up with broken pins and damaged backplates..I suggest you use the KB crank, even if their fit in the case is very loose and the radial play is embarrassingly large...I wish Bernie and Matt changed the blueprint for the aftermarket KB cranks, that would help sustain reedie speeds 25+k and higher...I personally do not like the aftermarket KB cranks because of their very sloppy fit.

Contrary to the common belief that loose fit KB shafts help boost engine speed, the radially unsupported shaft will wobble even with the best balanced prop, due to the unbalanced radial forces of the piston rod acting through the pin..a few years back Matt replied to me saying once the aftermarket KB shafts he then had on stock all sold, he will reorder a new run with tighter fit. I am not sure if the currently sold KB shafts have tighter fit, anyway, a properly fit KB shaft could well serve reedie performance experiment with unloaded shafts (e.g. only a  flywheel) like yours, Roddie.

Hi Andras, Thanks very much for your input. It was very strange when the engine suddenly stopped in the 2nd vid. It was screaming just prior.. then "sagged" from being leaned too much. It felt like it was seized.. but then loosened-up. I'd never experienced that. I was able to re-start it.. and ran it "rich" for a few seconds and then figured it was better to stop and give it a rest.

Nothing "broke".. but I suppose that there was some damage done. I'll disassemble the engine to inspect and report my findings. The backplate/carb. is of the type that has the "snap-on" plastic ring-type reed-holder. It will be interesting to see if it got damaged. I sourced an excess-stock of them when I sourced the backplate assemblies a few years ago.

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Post  roddie Mon May 20, 2024 6:14 pm

getback wrote:roddie did you find the crank pin broken in the engine ? Here is the discussion about the KB > https://www.coxengineforum.com/t10733-killer-bee-crankshaft?highlight=killer+bee
Is that a car engine case and crank ?

Hi Eric, Nothing's "broken".. because I re-started and ran the engine shortly after the incident. The engine was initially a 2nd-hand/late-model Babe Bee.. (slit-exhaust-port/dual-bypass cylinder/single-nipple backplate) See also my original post comments on the engine. HERE

audio-tach anyone? Dsc04316

audio-tach anyone? 20240561

I just swapped-out the 5cc tank-back-end for a choke-tube backplate for testing the velocity-stack/flywheel/heatsink combo.

audio-tach anyone? 20240563

I "do have" a car-engine that rsv1cox (Bob) gave me a while back.. which may be a better choice for running a high-rpm/flywheel application. These recent bench-runs are to help me configure/manage a marine engine conversion.

audio-tach anyone? Cox_0412
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Post  944_Jim Mon May 20, 2024 11:17 pm

As a marine engine it will need airflow or water cooling to keep from frying. May I suggest cutting down and drilling out a Pee Wee prop  and using a longer screen to hold it with the flywheel? Just some air flow will allow the engine to survive those test runs.


Last edited by 944_Jim on Tue May 21, 2024 2:38 am; edited 1 time in total (Reason for editing : Test runs)

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Post  F4D Phantom II Tue May 21, 2024 4:03 am

Hello roddie
                      I have been messing with the audio app on my phone and finally got a good reading on your second video of 24607 rpm at the end of the video before it quit. My audio tach is not working well. I need another for my i phone.
                                                                                     Juan
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Post  roddie Tue May 21, 2024 4:09 am

F4D Phantom II wrote:Hello roddie
                      I have been messing with the audio app on my phone and finally got a good reading on your second video of 24607 rpm at the end of the video before it quit. My audio tach is not working well. I need another for my i phone.
                                                                                     Juan

Thanks Juan!! Yea.. that # is closer to what Brad and Andras measured. BTW... check out my "tear-down" thread if you haven't already. Interesting what I found..
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