How to post, how to add pics, how to add an attachment, and how to share a YouTube video...


Author Topic: Wood bar dyno  (Read 4820 times)

Offline flyover1974

  • Full Member
  • ***
  • Posts: 61
  • Total likes: 11
  • New Member
  • OS:
  • Windows NT 10.0 Windows NT 10.0
  • Browser:
  • Firefox 53.0 Firefox 53.0
Wood bar dyno
« on: June 19, 2017, 04:41:05 AM »
Hi,

i bought a very nice propeller design program that calculates as well a wood bar dyno.
See screenshot.
My question now is how interprete the numbers...i dont really understand what is what.
On the example in the picture please someone can help me ?
It means the lengt of the bar is 879mm but what the he... is x-section ?

Please help.
Thank You
Hermann

Offline wojtekseta

  • Full Member
  • ***
  • Posts: 41
  • Total likes: 0
  • Plans holder
  • OS:
  • Windows XP Windows XP
  • Browser:
  • Firefox 52.0 Firefox 52.0
Re: Wood bar dyno
« Reply #1 on: June 19, 2017, 05:48:13 AM »
Block of wood has a square cross-ection. X-section is a lenght of square sides. They are equal 1/15th of the lenght of the bar.
Wojtek.
Wojtek LE XL G-19

Offline Tom H

  • Beta testers
  • ***
  • Posts: 398
  • Total likes: 87
  • Built/flew LEU, built/flying DE
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Firefox 53.0 Firefox 53.0
  • Eagle Type: DE, LEU
Re: Wood bar dyno
« Reply #2 on: June 19, 2017, 06:06:50 AM »
flyover, therewsas a lot of discussion of the wood bar dyno on the site years ago.  I made one for our LEU Treehugger and there was once a set that was being loaned around for general use.
To use to get a traditional dyno graph, you have to make a series of bars to load the engine across a range.  Then, run each bar at full throttle and note the rpm.  Using the program you can derive the HP for that particular rpm.  Then change the bar to another and repeat.  You should then be able to plot the rpm/hp points on a graph and get a dyno curve.  The more different sized bars, the more data points.  Crude, but should give a reasonable idea of the engine capability.

We found our half VW had 29 hp at 3390 rpm (used only one size bar).  We never got to 3390 rpm when using the prop, so our engine was developing less than 29 hp during TO and flying, and was only barely adequate when the wind/weather was good.
Tom H
Stubby, a BDE
Treehugger, LEU

Offline flyover1974

  • Full Member
  • ***
  • Posts: 61
  • Total likes: 11
  • New Member
  • OS:
  • Linux Linux
  • Browser:
  • Chrome 55.0.2883.91 Chrome 55.0.2883.91
Re: Wood bar dyno
« Reply #3 on: June 19, 2017, 10:19:13 AM »
Thank You guys,

I want to go on with engine tests at my home on 6000 ft to understand how many horses of the 45 i loose there. Than i would test down on 2300 ft...thats the minimum i can without driving for hours to get deeper :)

Now i have a special request on people that work with Solidworks or Rhino3d:
The prop design program have .txt files output and there is written, its possible to read it with the programs above. I think it gives only five 2d cuts of the blade from root to tip and than the 3d program interpolate it to a 3 dimensional corpus?
Is that correct?
Here a screenshot of the output.

Hermann

Offline flyover1974

  • Full Member
  • ***
  • Posts: 61
  • Total likes: 11
  • New Member
  • OS:
  • Linux Linux
  • Browser:
  • Chrome 55.0.2883.91 Chrome 55.0.2883.91
Re: Wood bar dyno
« Reply #4 on: June 19, 2017, 11:50:19 PM »
Thank you for explanations. So i know what to do.

Hermann

Offline Armilite

  • Newbie
  • *
  • Posts: 3
  • Total likes: 3
  • New Member
  • OS:
  • Windows NT 10.0 Windows NT 10.0
  • Browser:
  • Chrome 72.0.3626.109 Chrome 72.0.3626.109
Re: Wood bar dyno
« Reply #5 on: February 15, 2019, 12:45:53 AM »
Hi,

i bought a very nice propeller design program that calculates as well a wood bar dyno.
See screenshot.
My question now is how interprete the numbers...i dont really understand what is what.
On the example in the picture please someone can help me ?
It means the lengt of the bar is 879mm but what the he... is x-section ?

Please help.
Thank You
Hermann
=====================================================================
Wood Bar Dynamometer
Test club is square cross section, Width = Length / 15
HP = 0.0532 x (dia/450)^5 x (rpm/1000)^3

The way I understand it.
Your Test Club 1030mm / 25.4 = 40.5511811023622" call it 40".

HP = =SUM(0.0532*(B5/450)^5*(E5/1000)^3)

 

EaglersNest Mission Statement:
To maintain the comprehensive searchable database resource for Builders and Fliers of Leonard Milholland ultralight airplane designs aka Legal Eagle Ultralights.

BetterHalfVW.com  becomes LegalEagleAirplane.com - stay in contact with Leonard and get plans for all the Milholland Designs at LegalEagleAirplane.com
SimplePortal 2.3.7 © 2008-2025, SimplePortal