audio-tach anyone?

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

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).

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

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.

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 ?

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