Cox Engines Forum
You are not logged in! Please login or register.

Logged in members see NO ADVERTISEMENTS!


Dynomometer build (for air-screws) - Page 2 Cox_ba12




Dynomometer build (for air-screws) - Page 2 Pixel

Log in

I forgot my password

Search
 
 

Display results as :
 


Rechercher Advanced Search

Latest topics
» Indexing COX cylinders
by balogh Today at 1:10 am

» 1/2a Skyray plans?
by 944_Jim Yesterday at 10:14 pm

» Postage stamp backplates
by JPvelo Yesterday at 8:52 pm

» my attempt at making an exhaust throttle for Cox .049
by roddie Yesterday at 8:20 pm

» Another of C.T. engines cleaned ---- Cox Tee Dee .09 --- Just today (3/26/2024) more Cox parts
by sosam117 Yesterday at 6:58 pm

» Cosmic Winds, - Big Guy, Little Guys, Silver Guy and Wounded Guy.
by rsv1cox Yesterday at 5:18 pm

» My friend Ramón, his Cox .09 & Cox .010
by MauricioB Yesterday at 12:31 pm

» Introducing our Cox .049 TD Engines
by Cox International Yesterday at 12:27 pm

» Parts Cox TD-4
by rsv1cox Yesterday at 8:40 am

» STUKA bomb dimentions needed
by latole Yesterday at 7:43 am

» On ebay a very special Cox engine
by davidll1984 Yesterday at 6:32 am

» Introducing the new - "QZ" RR-1
by Admin Yesterday at 12:51 am

Cox Engine of The Month
March-2024
balogh's

"COX Budapest" .049 engine



PAST WINNERS
CEF Traveling Engine

Win This Engine!
Gallery


Dynomometer build (for air-screws) - Page 2 Empty
Live on Patrol


Dynomometer build (for air-screws)

Page 2 of 3 Previous  1, 2, 3  Next

Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  roddie Thu Jan 16, 2014 8:01 am

Surfer_kris wrote:
roddie wrote: It was important for Aeromodeller Magazine to test the Tee Dee .049 in 1962.. and state it's output power (bph/watts) and maximum torque (ounce/in.) at given rpm's.. on specified fuel. How do you suppose they came up with their numbers?  

Roddie

I think they ran a calibrated flywheel (with known inertia) and measured the rpm as the engine accelerates. From that you can then calculate the power and torque vs rpm.

You're probably right Kris.. If you follow my threads, you'll notice that I tend to be a "tinkerer". I enjoy experimenting with my own designs/concepts. I'm not what you'd call "well read" by any means. Sometimes I make statements based on how I think something should work.. rather than proven theory. The fact is; I enjoy "tinkering".. and sharing my experience with others.

This Dyno-build.. I feel may be helpful to me on several levels; as I also experiment with throttles and a homemade muffler for the Cox .049. The "muffler" has a large degree of adjustable flow/back-pressure; through the use of varying orifice pipes that can be changed quickly. I think that recording "static thrust" measurements with different pipes will prove interesting as opposed to running an engine with open-face exhaust. The throttle that I'm experimenting with; is not an exhaust throttle... it's a venturi-needle/plunger pioneered by "Ralph Cooney" and was marketed by "Ace RC" under their p/n 630. It works with "Bee-style" back-plates and meters fuel and air.

Surely I could just mount an engine on a block of wood and run it; taking tach measurements.. but to "me", it's far more interesting to have more information. For those who dismiss this work as a waste of time... they have a choice to ignore my efforts altogether.. or view them for entertainment value. If my sharing of information through experimentation (whether successful or not..) helps another modeler... or improves the usability of a Cox engine... then it's time well spent in my opinion.

Roddie
roddie
roddie
Top Poster
Top Poster

Posts : 8155
Join date : 2013-07-17
Age : 64
Location : N. Smithfield, Rhode Island

http://www.stilburnin.com

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  Surfer_kris Thu Jan 16, 2014 8:51 am

It is a hobby so there is no wasted time, by definition. Smile
I was just curious regarding the purpose of this entrapment...

There is a tread on RCU (by combatpig) regarding different props and their static thrust;
1/2a thrust-o-meter

(I just realized that that thread is about ten years old, time goes fast...)
Surfer_kris
Surfer_kris
Diamond Member
Diamond Member

Posts : 1893
Join date : 2010-11-20
Location : Sweden

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  Exsanitary Thu Jan 16, 2014 10:04 am

I am following your build, experiments like this are a great part of the hobby. I'm sure your results will be usefull.
Exsanitary
Exsanitary
Moderate Poster
Moderate Poster

Posts : 28
Join date : 2012-02-06
Location : Palominas, Arizona

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  ian1954 Sun Jan 19, 2014 4:39 pm

ian1954 wrote:

I admire the efforts made by Roddie and am watching them closely. I will follow his progress, learn from his mistakes, copy his design, improve it and build a better one! Very Happy !!

I did warn you! I have turned the motion through 90 deg, replaced the wood with plastic and metal, solved the problem of the upside down reading and fitted bearings for the swingy bit.

Still work in progress but it is now known, in honour of the inspiration provided. as the "Roddiemometer".

Dynomometer build (for air-screws) - Page 2 Roddie10
ian1954
ian1954
Diamond Member
Diamond Member

Posts : 2688
Join date : 2011-11-16
Age : 69
Location : England

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  roddie Sun Jan 19, 2014 6:28 pm

ian1954 wrote:
ian1954 wrote:

I admire the efforts made by Roddie and am watching them closely. I will follow his progress, learn from his mistakes, copy his design, improve it and build a better one! Very Happy !!

I did warn you! I have turned the motion through 90 deg, replaced the wood with plastic and metal, solved the problem of the upside down reading and fitted bearings for the swingy bit.

Still work in progress but it is now known, in honour of the inspiration provided. as the "Roddiemometer".

Dynomometer build (for air-screws) - Page 2 Roddie10

Impressive sir!!! Are those threaded rods/fittings leftover from your printer-build?
roddie
roddie
Top Poster
Top Poster

Posts : 8155
Join date : 2013-07-17
Age : 64
Location : N. Smithfield, Rhode Island

http://www.stilburnin.com

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  pkrankow Sun Jan 19, 2014 6:47 pm

Roddie, That's a proven arrangement. Looking good!

Ian, that prop looks dangerous...

Phil
pkrankow
pkrankow
Top Poster
Top Poster

Posts : 3025
Join date : 2012-10-02
Location : Ohio

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  ian1954 Mon Jan 20, 2014 3:09 pm

The threaded rods, M8 thread, are remnants from the printer build. All the plastic stuff is newly "designed" and built. The bearings modified slightly from my balance gadget - a flat bottom added.

Trying to work on a "universal" motor mount for quick attach and detach and the associated series of prints. That will be trial and error.

As usual, with anything I do, there will be a lot of trial and error.

I use M6, M8 and M10 studding quite a lot. It is cheap and very useful for make clamps, hold downs, frames ..........easy to get in most hardware stores or builders merchants.

Metric taps an dies are quite cheap here as well.
ian1954
ian1954
Diamond Member
Diamond Member

Posts : 2688
Join date : 2011-11-16
Age : 69
Location : England

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  ian1954 Mon Jan 20, 2014 3:10 pm

pkrankow wrote:Roddie, That's a proven arrangement.  Looking good!

Ian, that prop looks dangerous...

Phil

When I have sorted the motor mount - I will show you a dangerous propeller!
ian1954
ian1954
Diamond Member
Diamond Member

Posts : 2688
Join date : 2011-11-16
Age : 69
Location : England

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  roddie Mon Jan 20, 2014 4:38 pm

pkrankow wrote:Roddie, That's a proven arrangement.  Looking good!

Ian, that prop looks dangerous...

Phil

C'mon Phil... what's so dangerous about a prop with a serrated edge?  Laughing "Can I help you?" ... "Why yes.. I'll take one of those 8 x 4 Ginsu's please"  tongue 

Roddie
roddie
roddie
Top Poster
Top Poster

Posts : 8155
Join date : 2013-07-17
Age : 64
Location : N. Smithfield, Rhode Island

http://www.stilburnin.com

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  Surfer_kris Tue Jan 21, 2014 8:47 am

The one from Ian can have a second use, just turn the engine by 90° and you can measure the engine torque too. Wink
Take an rpm reading and you have the BHP...

Here is some useful info regarding torque measurements and different props; http://modelenginenews.org/techniques/testing.html
Dynos; http://www.clcombat.info/dyno.html

Dynomometer build (for air-screws) - Page 2 Am940425
Surfer_kris
Surfer_kris
Diamond Member
Diamond Member

Posts : 1893
Join date : 2010-11-20
Location : Sweden

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  roddie Tue Apr 22, 2014 12:08 am

I'm not much further along with this.. but today the weather was nice.. and I needed to fuel-proof it. It was too much to do inside this past Winter. Plus.. I wanted to resurrect the thread, because Ian was working on his own design.. and I'm curious if he's made progress.

To recap; this design uses a horizontal "beam" that pivots on a pin in the center, with engine/motor mounted on the left side facing forward.. and a digital hanging scale on the right side for measuring the amount of "pull" on the beam in ounces/grams.

Remaining steps for functionality are; fabricating an adjustable mount for a fuel tank, mounts for the scale and a tach.. and mounting a power panel. Calibration will be done using a second identical scale. Scales will be mounted for calibration on opposing sides/ends of the beam.

So far I have two interchangeable mounts for running Cox .049 reed-valve engines. One is for the horseshoe back-plate and the other is for the Bee-style tank-back-plate.

Dynomometer build (for air-screws) - Page 2 4-21-110
Dynomometer build (for air-screws) - Page 2 4-21-111
roddie
roddie
Top Poster
Top Poster

Posts : 8155
Join date : 2013-07-17
Age : 64
Location : N. Smithfield, Rhode Island

http://www.stilburnin.com

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Ian's thrust/stress meter

Post  VUgearhead Tue Apr 22, 2014 1:39 am

Another very useful function of Ian's design - when thoroughly fed up, simply rotate the engine arm out of the way. Then bang your head against the measuring thrust plate and VIOLA! An empirical reading of your frustration level!

To be scientifically precise, stress levels should be measured in beers.

VUgearhead
VUgearhead
Gold Member
Gold Member

Posts : 155
Join date : 2013-07-02
Age : 56
Location : Boynton Beach, FL

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  roddie Tue Apr 22, 2014 8:45 am

VUgearhead wrote:Another very useful function of Ian's design - when thoroughly fed up, simply rotate the engine arm out of the way. Then bang your head against the measuring thrust plate and VIOLA! An empirical reading of your frustration level!

To be scientifically precise, stress levels should be measured in beers.


That Ian..... he thinks of everything... always trying to "one-up" me...  Head Bang Head Bang Head Bang  Laughing 
roddie
roddie
Top Poster
Top Poster

Posts : 8155
Join date : 2013-07-17
Age : 64
Location : N. Smithfield, Rhode Island

http://www.stilburnin.com

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  SuperDave Tue Apr 22, 2014 8:58 am

Roddie:

Being trumped in the humor department is so sin.  lol! 

SD
SuperDave
SuperDave
Rest In Peace
Rest In Peace

Posts : 3552
Join date : 2011-08-13
Location : Washington (state)

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  roddie Sat May 10, 2014 11:15 am

OK.. some more progress. The "beam" design has had calibration posts installed, that hold two identical scales in suspension; one being solid-mounted and the other tensioned by a spring or rubber band. This yielded a .2oz. variation from one side of the beam to the other. That's pretty close considering the variables that I cannot control. The left hand scale and post are temporary for this purpose only.

Dynomometer build (for air-screws) - Page 2 5-10-110


I mentioned how I felt that a "floating" fixture should be the most accurate for pulling on a scale-hook.. so I made one. The tub is just a small rectangular plastic bin with a block of 1.5" thick foam-board cut to fit with only slight side-clearance and a couple inches of linear travel in the direction of thrust/scale-hook pull. Approximately 2 liters of water floats the fixture to a height where the two scale-hook mounts are level. I made a mount for an external fuel tank, swappable to either dyno.. which is height adjustable and also swivels. My homemade muffler is shown on a .049 prod. engine here, with an exhaust extension (bendy straw) routed down through a hole in the foam float. All the other parts to both dynos are standard hdwe. items and wood pieces.. and it's just a matter of size/alignment to build either of them. All parts have been fuel-proofed and ready for testing.

Dynomometer build (for air-screws) - Page 2 5-10-111
Dynomometer build (for air-screws) - Page 2 5-10-112
roddie
roddie
Top Poster
Top Poster

Posts : 8155
Join date : 2013-07-17
Age : 64
Location : N. Smithfield, Rhode Island

http://www.stilburnin.com

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  roddie Thu May 29, 2014 2:21 pm

Try not to laugh please... this was my 1st attempt.



"3rd time's a charm"... notice how it took me a bit to realize the engine had started backwards...  Embarassed 

Here's a 2nd try... average pull was 5 ounces @12-13K avg. rpm's with a 3-blade 5 x 3 prop on Sig Champion 25.



That uni-flow tank is one of the ones I made for my speed contest model. Capacity is 7.7cc. I think the cylinder/piston is pretty worn out by those tach #'s.. earlier tests with my muffler yielded an avg. 3 ounce pull while using x1 wide-open header-pipe with an exhaust extension running down through the floor of the float. It would barely needle into a 2-stroke. It was quiet though!
roddie
roddie
Top Poster
Top Poster

Posts : 8155
Join date : 2013-07-17
Age : 64
Location : N. Smithfield, Rhode Island

http://www.stilburnin.com

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  batjac Thu May 29, 2014 3:12 pm

Roddie, The tub's a great idea! It may not give absolute values, but it's a great way to do comparative testing for different prop/plug/shim/fuel combinations.  I may have to "borrow" the idea to test some combinations in the future.  At least for the next Reed Speed contest.  I just ordered a couple of those scales off of Amazon to test Cox stuff. Also, I can use them later in the year to weigh my luggage for a flight we're taking.


The Borrower Mark
batjac
batjac
Diamond Member
Diamond Member

2022 Supporter

2023 Supporter

Posts : 2332
Join date : 2013-05-22
Age : 60
Location : Broken Arrow, OK, USA

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  Cribbs74 Thu May 29, 2014 7:55 pm

Cool Roddie, very useful!
Cribbs74
Cribbs74
Moderator

2022 Supporter

2023 Supporter

2024 Supporter

Posts : 11892
Join date : 2011-10-24
Age : 50
Location : Tuttle, OK

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  roddie Thu May 29, 2014 8:54 pm

batjac wrote:Roddie, The tub's a great idea! It may not give absolute values, but it's a great way to do comparative testing for different prop/plug/shim/fuel combinations.  I may have to "borrow" the idea to test some combinations in the future.  At least for the next Reed Speed contest.  I just ordered a couple of those scales off of Amazon to test Cox stuff.  Also, I can use them later in the year to weigh my luggage for a flight we're taking.


The Borrower Mark

Thanks for watching/commenting Mark and Ron. The "tub" with a floating fixture offers very little resistance for a scale reading. Notice that the scale sits on a plate mounted to the tub.. and I pull the fixture back before powering-up the scale, to allow it to "zero" itself before releasing the fixture to apply tension. The small zip-seal bag over the scale keeps it clean from oil in the prop-wash.

The next step is to mount that same engine/prop/tank combo on the beam-style dyno, and run it on the same fuel, to see if I get similar avg. readings on it's scale. Technically; if the engine rpm's are the same.. I should get similar scale-readings if the beam is calibrated correctly. The beam-style dyno will have a power-panel mounted to it, a "hands-free" cradle for the tach and has a "beam-lock" so that the scale can be "zeroed" prior to applying tension. I also need to mount a variable "weight-vessel" to the scale-side of the beam, to compensate for the engine-side's weight; which might be augmented by accessories such as a throttle servo/linkage at some point and calibrated by dual opposing scales.. which mounts have already been built and tested to give very close readings without a weight-vessel. The idea is to be able to dial-in accuracy.
roddie
roddie
Top Poster
Top Poster

Posts : 8155
Join date : 2013-07-17
Age : 64
Location : N. Smithfield, Rhode Island

http://www.stilburnin.com

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  RknRusty Thu May 29, 2014 9:37 pm

Dude, that's a great idea. What was the scale reading at it's max?

_________________
Don't Panic!
...and never Ever think about how good you are at something...
while you're doing it!


My Hot Rock & Blues Playlist
RknRusty
RknRusty
Rest In Peace
Rest In Peace

Posts : 10869
Join date : 2011-08-10
Age : 68
Location : South Carolina, USA

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  roddie Fri May 30, 2014 8:08 am

RknRusty wrote:Dude, that's a great idea. What was the scale reading at it's max?

Hey Rusty, Thanks! With that engine; I was seeing readings of 5.1 ounces @ 13K rpm's. Let's just say that if you were able to build an airplane; weighing less than (without it's engine).. what it's planned engine is capable of pulling.. then that airplane should (in theory) have "unlimited" vertical performance. This is just one of the useful aspects of building a test fixture such as this. Sure; there are a lot of factors that influence real-world performance.. but if you know your engine will pull a certain amount of weight "static" on the test fixture where the prop is loaded to the max... it should be some indication of how the model will perform when put into an abrupt climbing maneuver.. like the start of a square loop for instance.
roddie
roddie
Top Poster
Top Poster

Posts : 8155
Join date : 2013-07-17
Age : 64
Location : N. Smithfield, Rhode Island

http://www.stilburnin.com

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  Davenz13 Wed Dec 03, 2014 1:10 pm

Just saw this unit on another site and remembered this thread. It seems to me it might be easily converted for use with nitro engines maybe

http://hobbyking.com/hobbyking/store/__66623__Turnigy_Thrust_Stand.html?utm_campaign=141203.USE&utm_content=135957858&utm_medium=email&utm_source=EDM

Demo

https://www.youtube.com/watch?v=aizFyrzhbdY

Apparently price is about US$50 plus shipping. Seems a pretty cool item
Davenz13
Davenz13
Platinum Member
Platinum Member

Posts : 591
Join date : 2013-11-28
Age : 68
Location : Palmerston North, New Zealand

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  1/2A Nut Wed Dec 03, 2014 8:47 pm

Simple DIY thrust stand using a scale...

Dynomometer build (for air-screws) - Page 2 P1010010
1/2A Nut
1/2A Nut
Top Poster
Top Poster

Posts : 3402
Join date : 2013-10-20
Age : 60
Location : Brad in Texas

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  roddie Wed Dec 03, 2014 9:13 pm

Davenz13 wrote:Just saw this unit on another site and remembered this thread. It seems to me it might be easily converted for use with nitro engines maybe

http://hobbyking.com/hobbyking/store/__66623__Turnigy_Thrust_Stand.html?utm_campaign=141203.USE&utm_content=135957858&utm_medium=email&utm_source=EDM

Demo

https://www.youtube.com/watch?v=aizFyrzhbdY

Apparently price is about US$50 plus shipping. Seems a pretty cool item

Thanks for posting Dave. That's a pretty cool product! I think there were questions as to the "usefulness" of a thrust meter, when I started this thread.. but it really makes sense to me. Watching the vid, I can see where it's very useful for electrics.. and utilizing a watt-meter to get the most efficiency out of your system with a given prop.

A Winter project is in the works to build a test-tub (not tube.. tongue ) for testing marine-drives.. primarily for my Cox .049 reed-valve engines. The function is not for measuring thrust though. I want to be able to test various drive set-ups for strength, angle, height, surface-props vs. submerged etc. before they're mounted in a hull. Ideally.. the tub or tank (I don't want it to be too big) will be oval-shaped with an island sized to form a circular "trough" wide and deep enough to accommodate the drive-fixture and adequate water supply for the prop. This will set up a whirlpool to help relieve prop-cavitation. I may be able to simulate a chine's action/angle by mounting the entire drive on a mock-up of the hull's stern/chine-angle with height-adjustable pins at the front, to be lowered down to water level and actually plane-out the drive. It would also be a better test to see how a throttled engine might perform.

Probably just another one of my crazy notions.. Actually, plastic lawn-edging might work well for the walls. Huh... and if I can form the outer wall with the "finned" side in.. it may decrease turbulence.

Hey 1/2A nut.. Thanks for chiming-in. Do you have any experience using .062" flex-cable running in a 3/32" brass stuffing-tube? I have the materials.. and was wondering if it's possibly strong enough for a small Cox reed-valve .049 powered rigger that I'm building?
roddie
roddie
Top Poster
Top Poster

Posts : 8155
Join date : 2013-07-17
Age : 64
Location : N. Smithfield, Rhode Island

http://www.stilburnin.com

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  1/2A Nut Wed Dec 03, 2014 9:31 pm

Dumas uses 1/8in solid steel drive lines, 1in prop with 1in pitch so at .062in you are pushing it. When the flex cable winds up under load you have to make sure the raps are going the right direction to tighten as the prop loads up the line. A cut down Octura 27mm x 1.4in pitch to 24mm dia may keep the cable from breaking. 2mm wire drives can handle 70 to 100w tops you're at 1.6mm If you use a reed engine you maybe ok should be about 65w given a TD can do up to 80w.
1/2A Nut
1/2A Nut
Top Poster
Top Poster

Posts : 3402
Join date : 2013-10-20
Age : 60
Location : Brad in Texas

Back to top Go down

Dynomometer build (for air-screws) - Page 2 Empty Re: Dynomometer build (for air-screws)

Post  Sponsored content


Sponsored content


Back to top Go down

Page 2 of 3 Previous  1, 2, 3  Next

Back to top

- Similar topics

 
Permissions in this forum:
You cannot reply to topics in this forum