Kress Jets

[Cyclops]

I just got off of the phone with John Kress. He did not know about this forum. He will be checking in soon. Very easy person to work with. Changing my order with him was no problem. Dealt with him 3 years ago and he took a lot of time with me. I am very slow sometimes.:o

[watt_the?!]

In the best interest of fellow EDFers, and showing no bias towards any entity or manufacture...calling it how i see it..here goes:


i found him quite the opposite..evasive,unable to answer questions, unable to understand concepts such as power, current, amps and despite offering help in correcting his power matching application on his site (it simply is wrong) he got defensive. They tore him a new one at the other site.

Bob was quite the opposite.
Intelligent, informative, open, willing to discuss and share, but at the time very much intending to ''hand over'' the business to his son..understandably.

the prices have skyrocketed since Bob left, the impellers are almost impossible to balance, and the fittings come loose easily, crack the lexan and distort the tube. Plus the whole assembly is heavy.

They were good in the early 80s as a ducted fan amongst limited choices for glow engines, but nothing has changed since then. In fact the design and concepts were, as i understand, sold to wemotec...who used them to manufacture electric specialist impellers.

Tim.

[Cyclops]

I did today what I should have done years ago when I bought 2 709E impellors from Kress. They are not even close to being right. One has the back of the fins machined off near the hub. The other has a front raised hub machined off. One is badly out of balance, the other is tuneable. Thanks for the wake up call. Rich.

[roccobro]

Tim, I have no personal experience with Kress stuff, but that is exactly what I keep hearing. Another user on the other forum had a fit trying to balance his new unit. When he thought he had it down, he made a hole on the side of his fan shroud on teh first run up. THe problems seems to be something about machining the rotor adapter hole after it is injection molded??

Too bad...

ustin

[Son of Paleface]

Like I said ...dont waist yaw time with this ju**, They'r just trying 2 move into the EDF market with rehashed nitro stuff ,that wasnt very good in the first place

[roccobro]

S O P- Yes, your info was correct and corroborated. The way you presented it to the new purchaser was kinda harsh and if I had spent that kind of money, (even if it is junk) I wouldn't want to hear about it like that.

I owe you a thanks, I know now I won't be trying one out any time soon.

Justin

[Son of Paleface]

Yeah well after a few "armchair experts" think they know it all , one tends 2 be a bit less tacktfull , sorry if I greated a few edges , but as they say....
excreetum happens
You dont have 2 thank me , Im only try 2 help ...........

[watt_the?!]

huh?...must be missing something here..

[John Kress]

Put our outrunner fans next to any other fans of the same diameter, they are the most powerful and lightest fan on the market.

For an unbiased professional opinion see:
http://members.aol.com/kmyersefo/ampapr05/ampapr05.htm (http://members.aol.com/kmyersefo/ampapr05/ampapr05.htm)

An outrunner motor’s high torque combined with our 7 bladed fan rotor/impeller is perfect for this application. Our outrunner fans are also the only ones with a wide enough polycarbonate center body that both can contain the wider motors (up to 1.5”) and support the motor from both ends.

See most recent specifications:
http://members.aol.com/kmyersefo/ampapr05/ampapr05.htm (http://members.aol.com/kmyersefo/ampapr05/ampapr05.htm)


Sorry Tim we picked someone to some nitro testing over a year ago – sorry it wasn’t you, it was my father’s choice…

[watt_the?!]

all i see is a write up on the history of kress jets and a copy of the published specs on your site.

hardly professional opinion.

here at WattFlyer we value factual information, and expect that the claimant can explain the information, and back it up, and stand behind their product. You dont need to do this of course, but it goes along way when you do.

[watt_the?!]

Sorry Tim we picked someone to some nitro testing over a year ago – sorry it wasn’t you, it was my father’s choice…

please dont try to imply any personal campaign here, it is so far from the truth that it is offensive.

We could, i guess, do a head to head comparison between your fans and the other market fans...any objection?

[roccobro]

That is what is needed. Those who are looking for a power system need to know what to expect so they can choose accordingly. If no info is out there, they will spend their dough elsewhere.

Justin

[watt_the?!]

ok 709E fan as posted at kress-jets....im just posting the facts, no opinion here.

kress 709E fan
3 inch diameter (77mm approx)
thrust 17.3 oz (484grams)
power input 15.3 x 11.8 = 180W
weight incl motor = 5.8 oz = 162g.
price without motor $78US

performance index ( thrust-weight)/power in = 484-162/180 = 1.79 (grams per watt)
value index = performance index/cost = 0.023 (grams per watt per dollar)



Alfa Model Gen 2 fan 60mm diameter
thrust 18.5 oz (520g)
power input = 10 x 19 = 190W
weight incl motor = 3.5 oz (100g)
price without motor = $40US.

performance index ( thrust-weight)/power in/cost = 520-100/190 = 2.2 grams per watt
value index = performance index/cost = 0.055 (grams per watt per dollar)

Wemotec 50mm diameter fan
thrust = 17oz
power input = 250W
weight incl motor = 3 oz (86g)
price without motor= $23US.


performance index ( thrust-weight)/power in/cost = 476-86/250= 1.56
value index = performance index/cost = 0.068 (grams per watt per dollar)


Wemotec minifan 70mm
thrust (for 184W) = 16oz
power - over 600W possible
weight incl motor = 4.4 oz (123oz)
price without motor = $53US.

performance index ( thrust-weight)/power in/cost = 454-123/184= 1.8
value index = performance index/cost = 0.034 (grams per watt per dollar)


edit: separated indexes into performance and value

[BadTroll413]

What surprises me is this.....with all the interest in EDF these days you dont see any articles or comparisons written up in the magazines.....it would be interesting to see a hobby store or merchant get the equipment and do the tests. Then let the planes crash where they may.

[watt_the?!]

what comparisons do you want? ive got a database of plenty of info, and so has roccobro. the bottom line is that most commercial fans are efficient these days. It comes down to diameter and pitch basically. This is important as it defines what power at what rpm is required for efficient motor matching.

it is far easier to match an electric motor to a fan, as the fan indirectly demands the power needed. Whereas in an IC application, the engine has a finite power that can be supplied at any rpm- which is a function of the fuel, pipe and cylinder specs.

Tim.

[BadTroll413]

Good question. I do many things.....and when I research i usually find a great depth of information that relates to all aspects of what I need to accomplish.......I guess if I were to format it, I would do under the EDF for dummies format.....what are the basics? What is the measurable baseline constants? Wattage per oz of thrust and so on. What application is this best suited for? Power to weight ratios that work. What sizes of EDF relate to the size of plane? I ahve had many peple ask me how i figured mine out....and basically....I guessed at it from the info i had been reading. Im sure i got lucky.....but I have interviewed many shop owners, flyers, and supposed people in the know.....and to be honest....none of them seem to really know anything about the subject. And after quite a bit of research I ahve yet to find an article that would help someone build or design or modify a plane for this from scratch. I find this strange because in the magazines...you see many talking about the lack of builders as opposed to those gravitating toward ready to fly or ARF models.

Anyway I hope this was clear..if not let me know....I will be happy to respond as there is always more to learn in this hobby.

[watt_the?!]

a simple graph of thrust v power v rpm is all that is needed....you could probably put in efflux velocity on an axis there also, but it is a derivative of that raw data.

all the other aspects hold true as they do with non edf apps.

Tim.

[roccobro]

BT- It is kinda hard to make just one chart or comparison for an "intro to dummies" benefit. There are many ways to figure out what could work, and what will work. I always ask "what do you have already?" as like Tim says, there are so many possibilities. Motor doesn't make enough rpm? More volts. Too heavy a setup? Lighter/less powerful sometimes make a plane fly better. For an example, look at the GWS A-10. While the EDF-55's make good power (on BL of course) the plane was not designed to fly at 25 oz's (or 33 with 1:1 like Fiasco and others!). An EDF-50 equipped A-10 with some good 12mm BL motors will get you 16-20 oz's of thrust at less than 15 oz of AUW! (and would cost about $120 for everything to upgrade to)

Most of the time one is stuck with a plane requiring a certain size fan. There are now four 90mm fans (or more) that are common in use. "How much $$ do you have, and how much weight can it take?" would answer that question.

So, what plane do you have, what equipment do you own, and how much power do you want? :D

Wattage Power fan (65mm id 68mm od)
Thrust- 12.8oz (360g) (factory specs)
Power input- 12x11=132w
Weight- 4.13oz's (117g)
Price WITH motor- $25 (Viking on sale for $29 w/2 units=$15/ea and free plane)

performance index ( thrust-weight)/power in/cost = 360-117/132= 1.84
value index = performance index/cost = 0.073 (grams per watt per dollar)

REAL LIFE #'s NOW
Thrust- 360g
Power input- 189w
Weight- 117g
Price- $15 (or free!)

performance index ( thrust-weight)/power in/cost = 360-117/189= 1.28
value index = performance index/cost = .085 (or 1.28 if free:D) (grams per watt per dollar)

Justin

[roccobro]

Oh, and if I had spent big bucks on a Lehner, you bet I'd want to get another fan for the next plane that would be able to use it with a different combo of batteries.

Justin

[watt_the?!]

so the WPF is very good value then by the looks of things?

im going to have to get me one arent i?

[BadTroll413]

True...one chart wont do it....like you said...many things to consider, either way....its all fun. when I build the next plane.....I will hit you all up for info to build a fan system.

And yes.....too many projects and way to little time.

[easytiger]

In the best interest of fellow EDFers, and showing no bias towards any entity or manufacture...calling it how i see it..here goes:


i found him quite the opposite..evasive,unable to answer questions, unable to understand concepts such as power, current, amps and despite offering help in correcting his power matching application on his site (it simply is wrong) he got defensive. They tore him a new one at the other site.

Bob was quite the opposite.
Intelligent, informative, open, willing to discuss and share, but at the time very much intending to ''hand over'' the business to his son..understandably.

the prices have skyrocketed since Bob left, the impellers are almost impossible to balance, and the fittings come loose easily, crack the lexan and distort the tube. Plus the whole assembly is heavy.

They were good in the early 80s as a ducted fan amongst limited choices for glow engines, but nothing has changed since then. In fact the design and concepts were, as i understand, sold to wemotec...who used them to manufacture electric specialist impellers.

Tim.

All the stuff about off center holes, absurd and unuseable lexan shrouds, etc...
That was all true when Bob ran the company, too. Don't blame John.
I have had a fair amount of experience with Kress stuff, and I would not go near it again.