SMALL - espritmodel.com SMALL - Telemetry SMALL - Radio
Reply
Thread Tools
Old Feb 01, 2012, 10:31 PM
Who Dat!
GeetarJoe's Avatar
United States, LA, New Orleans
Joined Sep 2011
650 Posts
Quote:
Originally Posted by LesUyeda View Post
"-pleasant sound"

And I have found that to lead to a much more relaxed flying attitude (for me, anyway). Two strokes make me feel like I have a bee, or a chainsaw in my hands. Not so with a 4 stroke. Someone should be playing a waltz. I would never even consider going back.

Les
i feel the same. a 4 stroke is just mo-betta.
GeetarJoe is offline Find More Posts by GeetarJoe
Reply With Quote
Sign up now
to remove ads between posts
Old Feb 06, 2012, 12:07 PM
Zor
Suspended Account
Ontario,Canada
Joined Feb 2007
9,742 Posts
No response to my posting in five days ?

Zor
Zor is offline Find More Posts by Zor
Reply With Quote  (Disabled)
Old Feb 07, 2012, 09:42 AM
Registered User
United States, TX, Weatherford
Joined Dec 2006
1,689 Posts
I think you will find four strokes throttle better, that is they respond to the tranny a bit quicker. Many of the 3D guys swear by the OS 91. I have used the Magnum .91 and the Saito .91 and can not tell the difference in performance. I also use a YS 63 which is ever bit as powerful as the 91s. It is just that YS, OS and Saito cost a ton more than the Magnum (which was on sale the other day for $169). There are also Lasers from Great Britain and Chinese copies of the Magnum named ASP (virtually common).
Chip01 is offline Find More Posts by Chip01
Reply With Quote
Old Feb 07, 2012, 05:13 PM
Registered User
Toysrme's Avatar
Birmingham, Alabama
Joined Jun 2002
2,970 Posts
it does start due to being reversed into it's compression stroke.
(in the case of this big saito it'll fire first time, every time simply by plugging the muffler with your finger & turning the prop until fuel is dumping out of it)
it was not running backwards
it cut off when i grabbed the throttle trim tab and pulled it down.


there's nothing to put to rust. nor are there any questions about it. it's a very common method to starting large, high compression 4 stroke engines. people have done it longer than i've been flying (18 years).

if fact, i've still got an RCR article on the engine from it's original review were the reviewer did not like the "normal" procedure of grabbing a high torque starter. which the editor added an excerpt & addendum about them easily hand started by priming & bumping backwards into the compression stroke.




if you had ever done it, you would know the engine fires against your finger/stick. it's fairly easy to tell when a 16-18" propeller lights off against your fingers...
Quote:
Originally Posted by Zor View Post
Toysrme,

Your video is not very convincing.
In fact it seem to show that the engine does not start due to reverse compression.

Also it quickly quit perhaps due to reverse rotation that many fellows have reported in the past.

This is a subject I have considered in my mind for a long time. I just cannot see that reverse compression can give enough momentum to the prop to carry forward (proper direction of rotation) inertia to have the engine get sufficient compression in the proper rotation and reach the ignition point.

From what I see in your video using the chicken stick downward, I believe that you are passing the ignition point in reverse rotation compression and that reverse firing is what gives enough momentum to start the engine.

Nothing to do from reverse compression else than actually firing the engine. Not compression alone as many postings have led to believe.

Perhaps one day we may be able to put this matter to rest.

Zor
Toysrme is offline Find More Posts by Toysrme
Reply With Quote
Old Feb 08, 2012, 10:31 PM
Zor
Suspended Account
Ontario,Canada
Joined Feb 2007
9,742 Posts
Expression I do not understand

Quote:
Originally Posted by GeetarJoe View Post
i feel the same. a 4 stroke is just mo-betta.
GeetarJoe,

I have no idea what you mean by "mo-betta"

You or anyone care to explain ?

Zor
Zor is offline Find More Posts by Zor
Reply With Quote  (Disabled)
Old Feb 08, 2012, 10:37 PM
Zor
Suspended Account
Ontario,Canada
Joined Feb 2007
9,742 Posts
Quote:
Originally Posted by Toysrme View Post
it does start due to being reversed into it's compression stroke.
(in the case of this big saito it'll fire first time, every time simply by plugging the muffler with your finger & turning the prop until fuel is dumping out of it)
it was not running backwards
it cut off when i grabbed the throttle trim tab and pulled it down.


there's nothing to put to rust. nor are there any questions about it. it's a very common method to starting large, high compression 4 stroke engines. people have done it longer than i've been flying (18 years).

if fact, i've still got an RCR article on the engine from it's original review were the reviewer did not like the "normal" procedure of grabbing a high torque starter. which the editor added an excerpt & addendum about them easily hand started by priming & bumping backwards into the compression stroke.

if you had ever done it, you would know the engine fires against your finger/stick. it's fairly easy to tell when a 16-18" propeller lights off against your fingers...
Toysrme,

You have not written anything that explains what happens that can make the engine start in its proper direction of rotation by kicking it bacward, kicking it in the opposite direction of rotation.

What has "rust" to do in this subject ?

Zor
Zor is offline Find More Posts by Zor
Reply With Quote  (Disabled)
Old Feb 09, 2012, 01:01 AM
Registered User
Toysrme's Avatar
Birmingham, Alabama
Joined Jun 2002
2,970 Posts
what do you think happens when a combustion chamber full of fuel is raised up into a glowplug at many hundreds of *F without enough force applied by the user to push it past top dead center of the compression stroke?
  • some form of combustion occurs
  • pushes the piston back down and provided it did so with enough energy to complete the next 3 combustion cycles (EIC).
  • at which point the engine should be self running
it's really not complicated. im not sure why we're having trouble understanding the concept.
Toysrme is offline Find More Posts by Toysrme
Reply With Quote
Old Feb 09, 2012, 01:06 AM
Registered User
Toysrme's Avatar
Birmingham, Alabama
Joined Jun 2002
2,970 Posts
Quote:
Originally Posted by Chip01 View Post
I think you will find four strokes throttle better, that is they respond to the tranny a bit quicker. Many of the 3D guys swear by the OS 91. I have used the Magnum .91 and the Saito .91 and can not tell the difference in performance. I also use a YS 63 which is ever bit as powerful as the 91s. It is just that YS, OS and Saito cost a ton more than the Magnum (which was on sale the other day for $169). There are also Lasers from Great Britain and Chinese copies of the Magnum named ASP (virtually common).
yes the os 91's are very good engines. typically found with a pump. tho slightly more complex & some versions can be cantankerous. the pumped ones were *the* default pattern engine in much of the 90's.

4-strokes tend to have far better throttle response if you're comparing to 2-stroke engines of the same power, on props that are over-loading the 2-strokes.
Toysrme is offline Find More Posts by Toysrme
Reply With Quote
Old Feb 09, 2012, 12:46 PM
Registered User
Joined Jul 2011
72 Posts
Quote:
Originally Posted by Chip01 View Post
I think you will find four strokes throttle better, that is they respond to the tranny a bit quicker. Many of the 3D guys swear by the OS 91. I have used the Magnum .91 and the Saito .91 and can not tell the difference in performance. I also use a YS 63 which is ever bit as powerful as the 91s. It is just that YS, OS and Saito cost a ton more than the Magnum (which was on sale the other day for $169). There are also Lasers from Great Britain and Chinese copies of the Magnum named ASP (virtually common).
Magnum, ASP, SC, Evolution (and some other brand names) are all made by Sanye Machinery in China now days.
I think that Magnum was made by ThunderTiger in the past, but I could be wrong about that.
Sorry if I got of topic.
NitroVein is offline Find More Posts by NitroVein
Reply With Quote
Old Feb 09, 2012, 07:07 PM
Zor
Suspended Account
Ontario,Canada
Joined Feb 2007
9,742 Posts
Finally the truth come out

Red text inserted by Zor.

Quote:
Originally Posted by Toysrme View Post
what do you think happens when a combustion chamber full of fuel is raised up into a glowplug at many hundreds of *F without enough force applied by the user to push it past top dead center of the compression stroke?

I think that an ignition takes place and the piston comes down under the force of the burning fuel .
  • some form of combustion occurs
You finally admit that.
  • pushes the piston back down and provided it did so with enough energy to complete the next 3 combustion cycles (EIC).
Exactly what I have written before. Compression alone cannot make the piston reach the ignition pressure and temperature on the next compression which is the proper direction of rotation.
  • at which point the engine should be self running
Right on but an ignition was (is) needed in the reverse direction to have enough inertia to reach ignition in the proper direction.

it's really not complicated. im not sure why we're having trouble understanding the concept.

Ya _ _ _ I had the concept for a long time but you kept talking about compression when ignition was the needed occurrence.

End of discussion.
Glad you now realized what is really happening.

Enjoy

Zor
Zor is offline Find More Posts by Zor
Reply With Quote  (Disabled)
Old Feb 09, 2012, 08:34 PM
Registered User
MaverickP-51D's Avatar
United States, TX, Palestine
Joined Dec 2007
165 Posts
something odd about that fella....i flip my saito backwards to crank it too.
so dont tell me it wont fire and run foward if flipped backwards against its own compression.
MaverickP-51D is offline Find More Posts by MaverickP-51D
Reply With Quote
Old Feb 10, 2012, 07:13 AM
ARFs Are Me
TomCrump's Avatar
Traverse City, Michigan
Joined Dec 2005
11,888 Posts
"Back Flipping" is a common method to start glow engines. It's something that most experienced modelers have at least witnessed, if not tried themselves.
TomCrump is offline Find More Posts by TomCrump
Reply With Quote
Old Feb 11, 2012, 12:43 AM
Zor
Suspended Account
Ontario,Canada
Joined Feb 2007
9,742 Posts
Quote:
Originally Posted by MaverickP-51D View Post
something odd about that fella....i flip my saito backwards to crank it too.
so dont tell me it wont fire and run foward if flipped backwards against its own compression.
I did not see anyone here saying "it wont fire and run forward" _ _ _ Where did you see that ?

It appears to me that we have finally established that compression alone in the reverse rotation direction will not start the engine.

The reverse rotation compression has to reach ignition and fire to have enough momentum to kick the engine back to its first firing in the normal rotation direction.

It seems easy to see what is happening.

Zor
Zor is offline Find More Posts by Zor
Reply With Quote  (Disabled)
Old Feb 11, 2012, 01:19 AM
Registered User
Toysrme's Avatar
Birmingham, Alabama
Joined Jun 2002
2,970 Posts
if compression alone would "spring" the engine the other way it'd have perpetual motion. when you back it up against compression it must combust to make it cycle through and self sustain.
ill give you a high speed video at a later date. that particular cap in question is currently in back the shop awaiting a new fuel tank & throttle servo mount. (double sided sticky tape only lasted... almost 12 years). i replaced the tank last year, but the new tank was a crappy one i had laying around from a giant scale ARF & i had to pull it out due to it leaking profusely. (and don't really have a LHS i like buying from, so im in no hurry to buy another.)

mainly tho... it's far too cold now, i hate being cold & don't feel like playing with a bunch of 4-strokes out in the cold until i get good slow motion video.




make yourself a note & bring it back up to me in like a month or two when it's warm & i get caught up.
Toysrme is offline Find More Posts by Toysrme
Reply With Quote
Old Feb 13, 2012, 08:23 PM
Registered User
United States, CA, Barstow
Joined May 2004
183 Posts
Quote:
Originally Posted by 94'325is View Post
I'm sure this has been talked about to death already but I had a few questions:

I have a lot of experience with 2-Stroke Nitro engines as well as 2-Stroke gas engines. I am planning my next plane and I was thinking of a Decathlon in the .75-.90 size. All of my current planes are 3D from parkflyers to giant scale and I want to do a somewhat scale aerobatic plane. I was thinking of going simple route and doing a 2-Stroke nitro or potentially a smaller gas engine but 4-strokes have always interested me. I'd like to have a more scale sound and grunt.

Are 4-strokes any more reliable than 2-strokes? Also how do they compare for tuning purposes. I'm looking into the .90 size for 4-strokes.
Bottom line is cost of fuel and cost of engine.
flycatch is offline Find More Posts by flycatch
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Question 2 Stroke vs 4 Stroke engines greenshirtrwg Fuel Plane Talk 30 Aug 18, 2014 08:01 PM
Discussion 2 vs 4 stroke south.tx.dead.I Engines 103 Oct 20, 2011 08:08 AM
Discussion Glow: 2-Stroke vs. 4-Stroke alexkmmll Engines 80 Jul 01, 2011 10:19 PM
2-stroke vs. 4-stroke for speed deserttoad Fuel Plane Talk 4 Oct 16, 2002 07:39 PM
2-stroke vs. 4-stroke deserttoad Fuel Plane Talk 0 Jun 29, 2002 10:13 AM