I Feel Ripped Off
12-13-2006, 11:58 AM
#51
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RE: I Feel Ripped Off
Basil,
that is a brilliant little test rig!! Good job! We should all have one of these. My friend has the
test mount with the analoge gauge but I would prefer this one. Is that the Walmart digital gauge Jason made us aware of?
FYI, it is not often we can talk about the truth regarding jet motors here. I will now archive these pages as a web archive. Anyone needing copies if it get shut are welcome to pm or e-mail me for files.
Joe Kelley
that is a brilliant little test rig!! Good job! We should all have one of these. My friend has the
test mount with the analoge gauge but I would prefer this one. Is that the Walmart digital gauge Jason made us aware of?
FYI, it is not often we can talk about the truth regarding jet motors here. I will now archive these pages as a web archive. Anyone needing copies if it get shut are welcome to pm or e-mail me for files.
Joe Kelley
ORIGINAL: basimpsn
I don't think that testing the engine inside the aircraft is very effective. Here is a simple solution for testing your engine and power.
I don't think that testing the engine inside the aircraft is very effective. Here is a simple solution for testing your engine and power.
12-13-2006, 12:45 PM
#52
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RE: I Feel Ripped Off
ORIGINAL: HarryC
You make these things to individual sizes?!! I thought a machine would turn out a thousand tailcones the same and every engine gets exactly the same parts.
H.
ORIGINAL: WrenTurbines
One is to make the tailcone smaller.
One is to make the tailcone smaller.
H.
Harry,
the outlet on the tailcone is sized for each engine individually depending on temps etc and we are only talking of a fraction of a mm making the difference.
regards
Jason
12-13-2006, 12:55 PM
#53
RE: I Feel Ripped Off
Well, I had a P-120 turned up all the way (28#s) and replaced it with a Super Eagle that I turned down to 25# of thrust per the manual. The Super Eagle puts out substantially more thrust at the 25# setting then my 120 did cranked up to max.
This was/is in a Skymaster F-15 with a SM pipe so I feel the test conditions were fair to both. I also now have a lifetime warranty and I would say the finest service quality available.
Beave
This was/is in a Skymaster F-15 with a SM pipe so I feel the test conditions were fair to both. I also now have a lifetime warranty and I would say the finest service quality available.
Beave
12-13-2006, 01:08 PM
#54
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RE: I Feel Ripped Off
ORIGINAL: bevar
Well, I had a P-120 turned up all the way (28#s) and replaced it with a Super Eagle that I turned down to 25# of thrust per the manual. The Super Eagle puts out substantially more thrust at the 25# setting then my 120 did cranked up to max.
This was/is in a Skymaster F-15 with a SM pipe so I feel the test conditions were fair to both. I also now have a lifetime warranty and I would say the finest service quality available.
Beave
Well, I had a P-120 turned up all the way (28#s) and replaced it with a Super Eagle that I turned down to 25# of thrust per the manual. The Super Eagle puts out substantially more thrust at the 25# setting then my 120 did cranked up to max.
This was/is in a Skymaster F-15 with a SM pipe so I feel the test conditions were fair to both. I also now have a lifetime warranty and I would say the finest service quality available.
Beave
Original John Ligons
Static performance, thrust, fuel economy advertised are all good things to know and there are some good products out there including ours. The thing I think you should focus on is how does the engine perform in your aircraft and how the power is delivered. Are all engines that produce the same static thrust created equal? I think not. Do they deliver their power the same?
Static performance, thrust, fuel economy advertised are all good things to know and there are some good products out there including ours. The thing I think you should focus on is how does the engine perform in your aircraft and how the power is delivered. Are all engines that produce the same static thrust created equal? I think not. Do they deliver their power the same?
12-13-2006, 03:08 PM
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RE: I Feel Ripped Off
Harry,
Yes, we do have the tailcones turned out in hundreds by a machine! But as Jason explained, very small adjustments can make a difference and that is one of the many things which makes the SuperSport into an unusually powerful engine for its size. The tailcone fitted to the engine which was run at the GTBA would not be noticeably different from any other tailcone, to the untrained eye, but it was a tiny amount bigger than it should have been. That's why we aren't able to produce the SS as a kit - it needs the experienced hands and eyes to make all the critical adjustments.
Sara Parish
Wren Turbines
Yes, we do have the tailcones turned out in hundreds by a machine! But as Jason explained, very small adjustments can make a difference and that is one of the many things which makes the SuperSport into an unusually powerful engine for its size. The tailcone fitted to the engine which was run at the GTBA would not be noticeably different from any other tailcone, to the untrained eye, but it was a tiny amount bigger than it should have been. That's why we aren't able to produce the SS as a kit - it needs the experienced hands and eyes to make all the critical adjustments.
Sara Parish
Wren Turbines
12-13-2006, 04:05 PM
#56
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RE: I Feel Ripped Off
Sure, "performance can be different in the air".....but damn difficult to tell...and if yer making an apples-to-apples comparison between engines, then you start w/ known and like conditions: A test stand. And those numbers (e.g., static thrust) will be a very good indicator of the airbourne performance....which is much, much tougher to quantify.....even in the same exact airbourne installation.
Re test conditions (ambient temperature and pressure), for every 1000' increase in altitude, figure on losing as much as 3-4% thrust...same for every 10-degrees F increase (many factors involved but 3-4% fine is for our purposes). The 'Standard' is sea level and 59F...the conditions at which manufacturers (should) correct their performance to. Same percentage other way...i.e. on a 50-degree day you should see 3-4% gain in thrust. So, if a manufacturer says 10-pounds thrust under standard conditions, you might expect a total of 10-12 percent degradation at 70F and 2000'ASl...and actually measure around 9-pounds thrust. You can see that flying in Denver on an 80F day seriously degrades turbine performance..perhaps as much as 25%!
I can tell you that Wren is VERY conservative...a 44-Gold I tested at sea level and 40F measured 11.8-pounds, which is still around 11-pounds corrected to a standard day. So, even on an 80F day, sea level, that 44 would still be exceeding the Wren-advertised 10-pounds!
Ray
Re test conditions (ambient temperature and pressure), for every 1000' increase in altitude, figure on losing as much as 3-4% thrust...same for every 10-degrees F increase (many factors involved but 3-4% fine is for our purposes). The 'Standard' is sea level and 59F...the conditions at which manufacturers (should) correct their performance to. Same percentage other way...i.e. on a 50-degree day you should see 3-4% gain in thrust. So, if a manufacturer says 10-pounds thrust under standard conditions, you might expect a total of 10-12 percent degradation at 70F and 2000'ASl...and actually measure around 9-pounds thrust. You can see that flying in Denver on an 80F day seriously degrades turbine performance..perhaps as much as 25%!
I can tell you that Wren is VERY conservative...a 44-Gold I tested at sea level and 40F measured 11.8-pounds, which is still around 11-pounds corrected to a standard day. So, even on an 80F day, sea level, that 44 would still be exceeding the Wren-advertised 10-pounds!
Ray
12-13-2006, 04:51 PM
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RE: I Feel Ripped Off
The proper way to spec any product is for the manufacturer to down grade the specs by around 15%. We used to do that in the computer industry. That way you have a "safety margin" to meet the advertized specs.
Seems that (concluding from the above comments and other threads on rcu) Wren has got this right. They probably get all of their engines to deliver, say 19-20 lbs for the SS, to guarantee that "most" customers will get the advertized thrust!!! This, IMHO, is the correct marketing strategy and the right customer service for the long run.
Seems that (concluding from the above comments and other threads on rcu) Wren has got this right. They probably get all of their engines to deliver, say 19-20 lbs for the SS, to guarantee that "most" customers will get the advertized thrust!!! This, IMHO, is the correct marketing strategy and the right customer service for the long run.
12-13-2006, 06:11 PM
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RE: I Feel Ripped Off
ORIGINAL: Miniflyer
Hi guys
turbine thrust itself is dependent on many factors. Mainly there is ambient temperature and air pressure (=elevation). With a turbine running on a low pressure, hot day at 6000ft ASL you can expect SEVERE thrust losses compared to the same turbine running at sea level on a cool day. Most manufacturers will specify their thrust ratings at ISO....
Apart from that: most manufacturers have a "spread" which is pretty wide. Some will produce high thrust ratings while other (identical) turbines produce less. This is due to the tollerances in parts....you might get a good one, or you might have bad luck and grab a bad one. You can always send it back and request improvement, as well as a test protocol under what conditions the thrust was measured.
Aother thing is static and dynamic thrust. Adding a pipe will cause losses of some sort. The static thust can be increased, though, by allowing more venturi air into the pipe. You can gain up to about 10% by this. However, this slows your exhaust drastically....high end performance is decreased a whole lot (effective thrust is dependent on the difference in velocity of exhaust air and
aircraft velocity....the higher the exhaust velocity, the more thrust will remain at higher airframe speeds). If you are looking for better high end performance then scoot the pipe closer to the turbine. Temps will rise a bit, and static thrust will drop, but on the top end you will be scooting along a lot better. A bypass will also help this effect a bit.
Best regards
Hank
Hi guys
turbine thrust itself is dependent on many factors. Mainly there is ambient temperature and air pressure (=elevation). With a turbine running on a low pressure, hot day at 6000ft ASL you can expect SEVERE thrust losses compared to the same turbine running at sea level on a cool day. Most manufacturers will specify their thrust ratings at ISO....
Apart from that: most manufacturers have a "spread" which is pretty wide. Some will produce high thrust ratings while other (identical) turbines produce less. This is due to the tollerances in parts....you might get a good one, or you might have bad luck and grab a bad one. You can always send it back and request improvement, as well as a test protocol under what conditions the thrust was measured.
Aother thing is static and dynamic thrust. Adding a pipe will cause losses of some sort. The static thust can be increased, though, by allowing more venturi air into the pipe. You can gain up to about 10% by this. However, this slows your exhaust drastically....high end performance is decreased a whole lot (effective thrust is dependent on the difference in velocity of exhaust air and
aircraft velocity....the higher the exhaust velocity, the more thrust will remain at higher airframe speeds). If you are looking for better high end performance then scoot the pipe closer to the turbine. Temps will rise a bit, and static thrust will drop, but on the top end you will be scooting along a lot better. A bypass will also help this effect a bit.
Best regards
Hank
At the end of the day, who really gives a .................... whatever
Does your model fly ok with the said engine?.........I guess it does
There are too many variables, at the end of the day, it is a model aeroplane. Relax.............
If it fly(s) ok; Just fly and enjoy the thing - don't worry about it!
:-)
12-13-2006, 06:56 PM
#59
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RE: I Feel Ripped Off
I think it is very relevant!! Most jet heads make their turbine purchase decision based on advertised specs. We do that for many things including this hobby (servos, batteries, radios, engines..etc). As a result, if you think you are paying fo,r say 50 lbs of thrust and you get 45 lbs (purely for an example), then I think most modelers will be disappointed they are not getting their money's worth. On the other hand, they may buy a product, be happy with it, never question its specs accuracy and they will be loyal to that product...nothing wrong with that as long as they are happy...I know for myself I would like to get +/-10% of advertised spec for anything I buy.... To each his own!!!
12-13-2006, 07:33 PM
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RE: I Feel Ripped Off
ORIGINAL: Ehab
Most jet heads make their turbine purchase decision based on advertised specs.
Most jet heads make their turbine purchase decision based on advertised specs.
12-13-2006, 07:51 PM
#61
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RE: I Feel Ripped Off
I think it is very relevant!! Most jet heads make their turbine purchase decision based on advertised specs.
The proper way to spec any product is for the manufacturer to down grade the specs by around 15%. We used to do that in the computer industry. That way you have a "safety margin" to meet the advertized specs.
Based on what I have read and heard from people who have had their engines checked it seems that Brand A and Brand W turbines typically meet or exceed their advertised thrust numbers. Brand J turbines typically fall short.
Joe
12-13-2006, 09:16 PM
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RE: I Feel Ripped Off
I should have expalined that what I was talking about was internal engieering specs versus advertised customer specs. There was normally about 15% of margin to assure relaibility and accuracy. This 15% of margin was "designed into the requirements" of the product engineering specs and relaibility/quality specs....This also left some room for future product improvement. I doubt that alot of this is used in the hobby industry, but some of it should be!!
12-14-2006, 07:38 AM
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RE: I Feel Ripped Off
I would agree with Gordon that most people make their purchase decision on customer service, reliability and what the other guys fly locally, rather than just advertised specs. However, customers deserve accurate specifications that they can also take into account with all the other information.
I've said before that this is a difficult thing for us to talk about, as manufacturers. We believe in competition - it's good for the consumer and for the marketplace - but it must be FAIR COMPETITION. Misleading statistics - whether exaggerated thrust figures or the use of an arbitary "average" fuel consumption figure rather than an accurate full-throttle one - make comparisons impossible and are unfair on the companies who are honest with the public. If manufacturers have nothing to hide, then they can surely publish the correct figures. If manufacturers believe the true figures would not be acceptable to the public, the answer is to do more development work on the engine until it acheives the desired power and efficiency - NOT change the figures to make it look better!
Sara Parish
Wren Turbines
I've said before that this is a difficult thing for us to talk about, as manufacturers. We believe in competition - it's good for the consumer and for the marketplace - but it must be FAIR COMPETITION. Misleading statistics - whether exaggerated thrust figures or the use of an arbitary "average" fuel consumption figure rather than an accurate full-throttle one - make comparisons impossible and are unfair on the companies who are honest with the public. If manufacturers have nothing to hide, then they can surely publish the correct figures. If manufacturers believe the true figures would not be acceptable to the public, the answer is to do more development work on the engine until it acheives the desired power and efficiency - NOT change the figures to make it look better!
Sara Parish
Wren Turbines
12-14-2006, 08:26 AM
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RE: I Feel Ripped Off
ORIGINAL: WrenTurbines
However, customers deserve accurate specifications that they can also take into account with all the other information.
Sara Parish
Wren Turbines
However, customers deserve accurate specifications that they can also take into account with all the other information.
Sara Parish
Wren Turbines
Sara,
so why does my Supersport do 19lb rather than the 18lb quoted?
Jason
12-14-2006, 09:02 AM
#68
RE: I Feel Ripped Off
ORIGINAL: Gordon Mc
Man ... that's just not right !
I think you need to send it back, so that they can detune it for you !
ORIGINAL: jason
Sara,
so why does my Supersport do 19lb rather than the 18lb quoted?
Jason
Sara,
so why does my Supersport do 19lb rather than the 18lb quoted?
Jason
Man ... that's just not right !
I think you need to send it back, so that they can detune it for you !
12-14-2006, 09:39 AM
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RE: I Feel Ripped Off
I think I've got the essentials for buying a turbine, whats being said is that most manufacturers tell small lies or embellishments (but not all Sara!) So if you want the thrust of a 120 its best to buy a 160 because thats the only way to guarantee what you need thrust wise.
Don't buy any jet that has a fixed tank or fuel load because if you expect to fly 9 minutes with reserve and ends up 6 minutes thats your lookout for reading the adverts. Its not the figures that matter but the way the jet flys, except no manufacturer gives out turbines to customers to try out prior to buying. Do they?
None of this tosh matters, you've spent your $2000+ and that it doesn't perform as per spec is really your lookout. Strange, no one suggested this turbine should just go back to get sorted out.
Paul
Don't buy any jet that has a fixed tank or fuel load because if you expect to fly 9 minutes with reserve and ends up 6 minutes thats your lookout for reading the adverts. Its not the figures that matter but the way the jet flys, except no manufacturer gives out turbines to customers to try out prior to buying. Do they?
None of this tosh matters, you've spent your $2000+ and that it doesn't perform as per spec is really your lookout. Strange, no one suggested this turbine should just go back to get sorted out.
Paul
12-14-2006, 09:55 AM
#70
RE: I Feel Ripped Off
ORIGINAL: rcdriver22
Strange, no one suggested this turbine should just go back to get sorted out.
Strange, no one suggested this turbine should just go back to get sorted out.
I have privately doe this twice now, and I will do it here as well. I would suggest anyone who is not having success or is any way not happy with their product to please contact the manufacturer.
12-14-2006, 10:45 AM
#71
RE: I Feel Ripped Off
If I got a engine that delivered several lbs. less thrust than advertised, I would feel ripped off and the engine would be shipped back ASAP. If it still didn't delivered very close to the advertised thrust @ the advertised rpm (and temps), I would demand my money back!
I'm sure several turbine manufacturers is glad they customers don't do that...
We did a simple installed thrust test one day at the field earlier this year, and the test was very revealing.
The test was done hooking the planes up to a digital fish scale with a rope, and done on a flat and smooth tarmac surface.
Temperature was about 12-14c. Altitude around 150 meters.
I don't claim that the figures are 100% accurate, but they clearly show some big differences between engines in the same (claimed) thrust range.
Originally posted in [link=http://www.rcuniverse.com/forum/fb.asp?m=5065243]this thread[/link]:
18,9 kg / 41.58 lbs - AMT NL Olympus HP, C-ARF Lightning, stock pipe (probably starved for air by the small intakes)
16,5 kg / 36.30 lbs - Merlin MKII, Eurosport, stock single pipe
16,1 kg / 35.42 lbs - Merlin MKII, Eurosport, Tam's bi-pipe
13,8 kg / 30.36 lbs - SimJet Nexus, AW Cougar, stock single pipe
11,5 kg / 25.30 lbs - SimJet 3000, SM F-15, stock bi-pipe
11,2 kg / 24.64 lbs - Behotec JB 130, Yellow F-15, homemade single pipe
I'm sure several turbine manufacturers is glad they customers don't do that...
We did a simple installed thrust test one day at the field earlier this year, and the test was very revealing.
The test was done hooking the planes up to a digital fish scale with a rope, and done on a flat and smooth tarmac surface.
Temperature was about 12-14c. Altitude around 150 meters.
I don't claim that the figures are 100% accurate, but they clearly show some big differences between engines in the same (claimed) thrust range.
Originally posted in [link=http://www.rcuniverse.com/forum/fb.asp?m=5065243]this thread[/link]:
18,9 kg / 41.58 lbs - AMT NL Olympus HP, C-ARF Lightning, stock pipe (probably starved for air by the small intakes)
16,5 kg / 36.30 lbs - Merlin MKII, Eurosport, stock single pipe
16,1 kg / 35.42 lbs - Merlin MKII, Eurosport, Tam's bi-pipe
13,8 kg / 30.36 lbs - SimJet Nexus, AW Cougar, stock single pipe
11,5 kg / 25.30 lbs - SimJet 3000, SM F-15, stock bi-pipe
11,2 kg / 24.64 lbs - Behotec JB 130, Yellow F-15, homemade single pipe
12-14-2006, 11:33 AM
#72
RE: I Feel Ripped Off
I don't claim that the figures are 100% accurate, but they clearly show some big differences between engines in the same (claimed) thrust range.
12-14-2006, 11:35 AM
#73
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RE: I Feel Ripped Off
I have found that unless you have a well designed jet pipe set up you will loose thrust. I have a P70 and although I don't think for one minute that is doing what it should, it would certainly be doing more in a open install than the 14lb it's doing installed in a Bandit.
Jason
Jason
12-14-2006, 11:35 AM
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RE: I Feel Ripped Off
ORIGINAL: slick121985
Due to the overwhelming number of PM's i've gotten, i figured i'd post it here. The turbine in question is a new (June 06) P-120. Greg
Due to the overwhelming number of PM's i've gotten, i figured i'd post it here. The turbine in question is a new (June 06) P-120. Greg
Please check your PM and reply ASAP.
Best Regards
Ben
12-14-2006, 11:40 AM
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RE: I Feel Ripped Off
[/quote]
Original Mr Matt
I have privately doe this twice now, and I will do it here as well. I would suggest anyone who is not having success or is any way not happy with their product to please contact the manufacturer.
[/quote]
Mr Matt,
I think you are very brave,based on the results of a poll running at the moment and your suggestion for the customers to contact the manufacturer I would respectfully suggest your service department may be getting very busy, very soon.
jason
Original Mr Matt
I have privately doe this twice now, and I will do it here as well. I would suggest anyone who is not having success or is any way not happy with their product to please contact the manufacturer.
[/quote]
Mr Matt,
I think you are very brave,based on the results of a poll running at the moment and your suggestion for the customers to contact the manufacturer I would respectfully suggest your service department may be getting very busy, very soon.
jason