RPM?

[RodneyPierce]

 

[aaron alberico]

Rodney

I would say around the 31 -32000 range...

 

[dwilfong]

so it worked?

 

[Tom Foley]

NICE !!

 

[aaron alberico]

Rodney

You get any speeds on it?

 

[SayMikey]

Sounded like rpm but no mph

 

[Jeff Schindler]

Serious RPM in this video I found.

http://www.murnanmodified.com/newsdesk_info.php?newsdesk_id=137&osCsid=5c1545d9b169c05c4eb71fe4834e951d

 

[RodneyPierce]

Aaron, no speeds on it. Still saving for a good gun. I think its around 60 mph or so............

 

[RodneyPierce]

Jeff, thats INSANE rpm! haha.

 

[RodneyPierce]

Mikey, same prop and setup I had in Mendota. Prop is an H7 46.5mm diameter 3.74 cup. It needs cupped up more. RS carbon pipe at 7 inches. She is a turd, but slowly getting there. PROPS PROPS PROPS

 

[Greg Bonahoom]

Rodney,

Have you tried the 12 dollar 1450 mod prop from zippkits? I have tried numerous props on my jae .21 and most of them go about 61 mph. The zippkits prop straight out of the box does about 65. Worth a try if you haven't already. BTW, are you coming up to Minnesota for the race in early October? The b hydro class is getting pretty competitive up here.

 

[RodneyPierce]

Greg, I have not tried it.

And I do plan to come up in October. Should be a good time.

 

[hugh hargett]

Should be around 75 @ 30k ?

 

[hugh hargett]

Serious RPM in this video I found.

http://www.murnanmod...eb71fe4834e951d

looks like some 21 users could stand to have these mods nice "dyno" too - looks like they are popping up everywhere.

I think the boat in the video is running around 27,900 rpm based on some scope measurements

Rodney, if that guy below pulled over 50k then id think 27,900 is well you know 27,900. You should find a prop that allows the motor to run at the top of its rpm range which is likely higher than 27,900. if so adding more cup to your current prop may bog you down even more. A smaller diameter higher pitch may be the route to take.Based on some reputable literature out there theres a point that cupping decreases performance not saying your there yet.Just a reminder.

 

[anthony_marquart]

Mikey, same prop and setup I had in Mendota. Prop is an H7 46.5mm diameter 3.74 cup. It needs cupped up more. RS carbon pipe at 7 inches. She is a turd, but slowly getting there. PROPS PROPS PROPS

whatever,.. you know it's fast..

 

[RodneyPierce]

i just used the RPM app phil and hugh posted in another post, and it said a MAX RPM of 32076 with about 30500 average. I did it 5 times with nearly identical results. If those things work, thats awesome!!! I did the video of my 35 plus and it was consistent upper 33XXX RPM with a 1914. peaked at just over 34k. Ill have to mess with this a little more here this weekend!!!

 

[hugh hargett]

They should work fine coz all there doing is taking the period of the dominant frequency and mutilplying it by 60 or something along those lines. The smart phone have more than enough processing power to be as good as the small standalone devices you see out there. There are some schematics around for building an audio tach using a 555 timer. If you could are turning that h7 @ 34k she should be quite quick. I dont know the pitch of your 1914 shes likely still good and quick.

 

[anthony_marquart]

Now I need an Iphone!!! This could be a huge step forward in testing tools for the normal guy. Being able to do that between runs, adjusting the pipe between each one,.. then checking RPM,.. this would be a GREAT advantage in testing!

 

[Jeff Schindler]

Is the audio recording equipment of say a cell phone good enough to get the frequency +/- 5% ? What about Doppler effect which at 70 mph is about 8% each way? I think it would be better to get speed than RPM from the audio since that is relative to the change in freq vs the absolute measurement.

 

[RodneyPierce]

Jeff, how would you get speed from the audio? Please explain. Is there an app for that?