Kress Ducted Fan

[cbruder]

I`m looking for info on the Kress 740 Ducted Fan, rotor-assembly, installation, anything you could provide me with.

Thank you in advance,

cbruder

[pulsar110]

Take a look at Wemotec, they bought Kress and have the line now. You will find them there and they are in your neck of the woods.

[rahlberg13]

I've heard lot of rumors that people have bought Kress (including Electric Jet Factory). But I’ve talked to them recently and they are still trucking along. You’ve recently got a new (but very limited) website up. Check out www.kressjets.com.

[pulsar110]

Sorry my bad. I do know that Wemotec has the fans you are looking for. I saw them on their website last week.

[dingofarmer]

I purchase two several months ago, for os .15's serious fit problems and mods are needed. I have a kress a-10, nice kitt, but I'm having trouble with the fan units. Need help

[easytiger]

What diameter fans are you using in the A-10? Maybe the 95mm toki fans will fit instead?

Can I suggest you roll your own shrouds for the Kress? If you have the clear lexan shrouds, you are doomed to failure. They are not round, will never BE round, and will not stay round, and they will crack around every screw hole.
I have been around the block a bit with Kress fans, they are a pain.
The most succesful installations have been to just use the kress rotor and nothing else.

[easytiger]

If your A-10 was for the RK049 unit, then try two Kamdax 061 units instead...

[dingofarmer]

Thanks for the reply I belive they are the rk 49, I'll have to check when I get off of work. I have tried to dry fit everything and it seems like a mass amount of mod is needed. So just use the rotor and build a custom mount to the pylons, so clear plastic outer shell??? Its the primary thing that is causeing problems as well as routing to fuel lines from the fuse to each engine I'm worried that they will not have enough suction. Do I need a small pump?

[easytiger]

Yup. If you got the clear lexan shroud, it is useless. Once they routed out the hole for the cylinder head, it changed the stresses within the plastic, and it will not stay round.

You are running 15's? You will want pipe pressure, for sure.

I don't remember the Kress a-10 that well. What is it supposed to weigh, and what fans, when you get the chance?

If it is for the RK049, the Kamdax units will be dyamite. They are everything the kress is not. They assemble in half an hour, are dead reliable, self-contained, easy to mount, easy to start...just a dream.

I have dorked around with the RK049, as a matter of fact, I have the original one that Walt Musciano used on his F84 published in MAN, and it is a finicky thing, and makes a heck of a lot of noise and not a heck of a lot of power.

If your plane is for the RK709 or RK720, maybe the Toki units will fit. They are 95mmm..

Before you start in with the mass mods, make sure you have the right engine/fan combination first...

I seem to remember a review of this plane from back in the eighties, and they had a heck of a time keeping the engines running during launch. I had similar problems with the old Midwest A-4/RK049...

[dingofarmer]

I guess the down side is that I bought both units from kress, $150.00. kind of a let down. I will get that info this afternoon

[easytiger]

I know. I spent hundreds of dollars and many hours with kress, and very little flying.

[dingofarmer]

RK-709, fans, sorry it took so long. The os .15 is would need serious mods...I'm somewhat mad for even paying the money for those units.

[ROUTIER]

:) I can provide for you a notice and drawing plan for RK740 using OS 46 VRDF engines. I got two but I think that it will be necessary to ad major modification before using !

[easytiger]

Go sell the kress fans on ebay. Cut your losses!
Look into the Tokifan. One bummer is the pipes are going to stick way out the back of the nacelles...

[easytiger]

I'm rather skeptical of your claim of 4 pounds of thrust by simply changing your rotor from the Toki to the Kress.

Some problems here...

I saw over 30 different rotors prototyped and tested by toki. All machined out of barstock. Are you telling me that they did not try the stock RK one? Come on. Are you telling me that having spent tens of thousands of dollars on rotor design, that was the best they could come up with?

The fact that you are testing the Toki with only 10% nitro, what's up with that? That's absurd.

Do you have ANY flight time at all on the tokifan?

I have about four hundred flights on Tokifans, in a bunch of different airplanes. I have a new Pilot F1 prototype on my bench right now. While I do not call myself an "expert", I do speak from some experience.

I just cannot accept that you got four pounds of thrust simply by changing the rotor. That does not wash.

Please back it up with some hard data.

[easytiger]

Okay, I'll bite. I'll call up Kress and try a RK720 rotor.
There is just one rotor for the 720, a blue one?


The nitro...well, that has NOT been my experience at all. Both the OS/Kyosho unit and the Toki Fan perform markedly better with 30% heli fuel for me.

What have you done in the AIR with these tests? Static thrust is one thing, air miles is another.

I just put the finishing touches on the F1. Ready to go, but it is too cold here to fly it. Came in at the same weight as the DJ3, but has fixed gear.
Improved in many ways over the DJ3, but we shall see how it flies...

[easytiger]

Your graphs have me confused. Is all that data backed by testing, or theoretical?
Where is the graph for a Toki with a Kress fan, powered by an 18 engine, producing 4 pounds of thrust?

[easytiger]

"the biggest difference came from the tuned pipe... around 20-30%."

I'm not understanding that statement. Are you saying you tested without tuned pipes?

[easytiger]

"i'm secure with the findings and aso secure enough to know that we have derived thrust and power coefficients from the tests to enable prediction, and backed it with actual data."



In other words, NO. You did not actually test this. It's all theoretical.

And meaningless. Pretty graph that means nothing at all.

No amount of stochiometric calculation is going to change the fact that the plane flies better with more nitro. You can theorize all you want, but Joe High School Dropout down at the field is going to shake his head sadly and tell you that the real world proves you wrong.

So, again, how much airtime, exactly, have you put on the Tokifan? None?

[easytiger]

"i'm secure with the findings and aso secure enough to know that we have derived thrust and power coefficients from the tests to enable prediction, and backed it with actual data."


I.E...you are only PREDICTING the thrust. Which is IF the engine will turn the fan at that speed, THEN you will get that thrust.

All stuff which has ZIPPO to do with the real world.
I tested a Fantom 16 engine. In THEORY, it would do 44k. In REALITY, turning the Tokifan, it would only acheive 20.

Again, you say "the pipe is good for 20-30%"...
What does that mean? That you tested the engines without a pipe? What would be the point of that?

Do you actually have any experience with models?

[easytiger]

Okay. I checked out your website.
I gather you are a graduate student who got a grant?
I see the whole deal now. You are taking Aldous Yuen's Oakdale F-35, increasing the size a bit, and you want to make it into a Vtol.

Er...I seriously doubt it.

Did you talk to Eddie Weeks, or Eric Dainty, the two guys who have actually flown jet VTOL?

I understand now why you did not test with tuned pipes...the pipe will not let the lift fan articulate.

Unfortunately, the tuned pipe is NOT an OPTIONAL part of a high performance DF unit, it is INTEGRAL.

You are on the wrong path with this project, I seriously, seriously doubt that it will ever fly. These aircraft have a hard enough time in just forward flight, vertical lift? Come on. Simply weigh two fan units. One for lift and one for thrust. Then measure the thrust from one fan.

YES, I would like to hear your engineering credentials, I would be interested.

Eric Dainty spent years working on his harrier, he did get it to fly, but it was so critical, he could not even PAINT the aircraft, it was that close. This with an OS91, which is MUCH higher P/W than any 18 engine.

If you want Vtol, you should be talking turbine. Then the thrust is not an issue. You can focus on the stability and control systems, which are the parts that merit development.
Eddie Weeks's "Rig" flew very well indeed. he did some very interesting engineering solutions, very unrefined, but quite workable! He's brilliant, in his way. He just rolls up his sleeves and DOES it. And he has incredible success. His second Vtol plane is up for sale right now...

[easytiger]

Just got off the phone with Kress. Ordered a rotor.
Here is Kress's own data for the RK720 fan:
http://kress-jets.com/720g-pchart.htm

About 3.75 pounds at about 24k. Which was acheived with a K&B21, Macs pipe, and 25% nitro. The K&B is much more powerful than the Toki, there is no way I can see that the Toki is going to spin the Kress rotor faster with less power. Also, Kress knew about how vital the ducting was, he used a flared inlet, always, and a spinner, and there was always a boat-tail tank to smooth out the airflow.
I don't doubt that Bob's rotor is probably the most efficient of them all, he REALLY knows his stuff, design-wise. But to say that you can just bolt on the Kress rotor and get FOUR pounds of thrust out of a Tokifan, well...I don't think that is grounded in reality at all. But I will test it and see.
I think what will happen is this...
The Kress rotor will be WAY too much load for the Toki 18, and it will do 20k at the most.
If the K&B21, which is a pretty hot engine, refined from years of boat and car racing, can only turn the Kress rotor at 23k or so, why would the Toki turn it faster?

Been there, done that, with the Fantom 16 engine. It was a $250 waste of money. In THEORY, the engine can do 44,000 RPM. MAYBE, turning a flywheel with no load! But NOTHING like that in the real world.

I have a couple of tokis being blueprinted by my engine guru buddy Don Garry down in florida. Maybe I can send the Kress rotor to him, and he can port the engine to take this specific load. He is stalled right now because he does not have any rotors, I don't have any spares,and I shattered several over the years. Without the specific load that the engine will be using, like the toki or kress fan, he cannot set up the engines properly and test them.

[Mark Turner]

Originally posted by easytiger
He is stalled right now because he does not have any rotors, I don't have any spares,and I shattered several over the years. Without the specific load that the engine will be using, like the toki or kress fan, he cannot set up the engines properly and test them.

Curtis,

If you need a rotor to help Don out just take care of the shipping and keep me in the loop as far as how he is progressing.

And let me know that you find out on the Kress rotor but I'm with you on this one :rolleyes:

Someone e mailed me this picture a month or so ago but with no real details to it and I never responded they claimed it was a .27 or something like that but you can also see the motor mount beams extend past the Toki mount :p and the head way above the shroud....figured someone was tryin to get a rise out of me.

In anycase if you need a rotor or 2 just let me know. Hope all is well with you and yours!!

Thanks,
Mark

[easytiger]

I COULD use the rotor. I beleive then don will have enough stuff to reassemble TWO fan units, and he can do one with the Toki rotor and one with the Kress one. I'll find his adress, and you can send it right to him. I think one rotor will be fine, unless the kress does not work out at all.

I remember having to shave down the kress 709 rotor to unload it enough to get a TD09 to spin it up. It kind of defeats all that careful Kress rotor design, if you have to take a dremel to the trailing edge...chances are, the Kress rotor will need the same treatment.
I do not dispute, though, Bob Kress's experience with design, he DOES know his stuff. But translating that design theory into the real world, well, something is often lost in translation!

I have at least two shrouds, including one brand new one, if you can use them.

The larger engine is real, I think, I have to ask about that and get me one. What has me much, much more excited, though, is the new Toki Turbine. I am wheedling and begging to get one of the first, I don't mind paying for it. Within reason!

I passed up on a free DJ2, beleive it or not. It was just too ugly.

I do want to try an Oakdale F35, but I am also thinking I might try something completely scratchbuilt for the Toki, all balsa, light, and sized very precisely around the fan.

I will find don's adress, and I need yours...

[easytiger]

That engine in the foreground...the mounting thing, what's that? Also, the kress rotor shown has way too much rotor tip clearance, an unacceptable loss of efficency.

[Mark Turner]

Curtis,

No problem I have several NIP rotors for replacement parts. Address is on the Support page of RT Models. When you find his address send me an e mail and I'll get it to him via UPS.

Thanks,
Mark

[easytiger]

I see.

The Kress rotor arrives in a few days. Tell you what, I will install it on the brand-new Toki 18 fan unit that is on my F-1 and test it, after breaking the engine in with the stock rotor, before I send the kress rotor on to Don Garry.
If the Toki 18 will spin that Kress rotor up to the four pounds of thrust you claim, using 10% nitro, I will eat my nice high quality JetCat Hat, which is all sweaty fuel soaked and salty and nasty, from too many days out at the field last year.

[easytiger]

I'm not going to get into the interpersonal dispute portion of all this, they don't like it here, and I'm trying to behave.


I fly this stuff pretty extensively, and want my planes to fly better, is all.

Seems like you lost a pound of thrust between your first post and your last...

[easytiger]

I have NEVER cut anybody's head off. I was never convicted, it was never PROVEN, anyway...

You said very definitively in your first post that if you change the rotor on a Toki 18, you WILL get four pounds of thrust. Now you are saying something different?

My credentials, well, I have won Model Of The Month TWICE at the Hackensack Valley Swamp Rats Model Airplane Club in Moonachie, New Jersey. Won five bucks each time. Costs me six to cross The George Washington Bridge and get back home, though. Top THAT.

I really don't need to go to Langley and borrow any testing equipment. I can simply bring this Pilot F-1 up to my hangar upstate this weekend, fire it up with both different rotors, and tie my cheapo Zebco De-Liar Brand fish scale to the tail. It will certainly tell if the Kress rotor is putting out about DOUBLE the thrust of the stock one.
The F-1 has plenty of intake area, and it has a molded intake lip going around the front edge of the fan, and nothing for rear ducting, just open air, so there are no installation losses. Besides the installed losses would be the same for both rotors, so what would that matter?

[easytiger]

So, the short answer to all of this is NO, you have not actually done this.

All of your thrust claims are based upon pure prediction.

And you did NOT generate four pounds of thrust by changing the stock rotor to the Kress one. But you went ahead and told others that if they just bought a $20 Kress rotor, they would get four pounds of thrust.

"actually using the ration achieved by others who took the stock toki fan at 25k and 2.2 lb thrust and made it generate 28.95k, "

Who did that? Where did the extra 4000 revs come from?

[easytiger]

Originally posted by what_the?!
toki 0.18 with rk720.

4lb thrust.

simple install.

adaptor kit available.

www.skunkworx.com.au

There it is.

You also said that nitro did not matter...

[easytiger]

I ran this past a friend of mine who said that seven pounds of thrust would require 2.5 horsepower. How will you acheive that?

[easytiger]

Right. So, what engine is going to give you 2.5hp and 33k?

And please explain to me exactly what setup will let my toki 18 turn out four pounds of thrust with my new Kress rotor. I really want to know.

[easytiger]

So, I guess it was all baloney.

Hey, ace, if you ever need help, let me know. Some of us actually have experience USING this stuff, and will be glad to share this real world information with you. Good luck with your project.

I already ordered the rotor, so I will test it out.

[easytiger]

On to more interesting things...

Professor Rahlberg, you tested the complete RK720 with a Picco motor, right? What thrust did you end up getting?

[easytiger]

Someone emailed me the link to your RCU threads. You are a complete troll, and you have no experience, and you know nothing of what you are talking about. Nothing. All puffery and bull.

You got put in your place by better men than me, like Mr. Matt and David Reid, you tried to sell them the same bill of goods, and they did not buy it either.
I suggest you go play elsewhere. Maybe someone might call up the University of Adelaide or the Sir Keith Fund and tell them about this nasty young fellow who is using their grant money to buy toys.
Maybe someone can email the department head some of these threads. I right-clicked them to disk, just in case I feel like that.
I have a modelling friend who is the Dean of one of the other major Australian Universities, I'm sure he can place a call if needed to yours.

Anybody who wants to know what this person is all about, you can look him up on RCU, under the same name. It's not pretty, and he has not endeared himself to the community.

I'm not going to waste any more time with this person, he's not flying any jets, he's not serious, he is making up facts and figures as he goes along, there is no "we", no "staff", it's just him alone,there is not "Skunkworx Pty Limited" besides a small website, he's not an offcial Toki anything, he's not going to be flying any F-35 Vtol with Toki Fans, and...
You are not going to get four pounds of thrust out of your Toki by changing the rotor. Sorry.

He can continue on with the insults against me, who cares? Give them enough rope to hang themselves, I always say.

What I do care about is the quality of information, and his information is all nonsense. He has been told this before.

[what_the?!]

Originally posted by easytiger
Someone emailed me the link to your RCU threads. You are a complete troll, and you have no experience, and you know nothing of what you are talking about. Nothing. All puffery and bull.

You got put in your place by better men than me, like Mr. Matt and David Reid, you tried to sell them the same bill of goods, and they did not buy it either.
I suggest you go play elsewhere. Maybe someone might call up the University of Adelaide or the Sir Keith Fund and tell them about this nasty young fellow who is using their grant money to buy toys.
Maybe someone can email the department head some of these threads. I right-clicked them to disk, just in case I feel like that.
I have a modelling friend who is the Dean of one of the other major Australian Universities, I'm sure he can place a call if needed to yours.

Anybody who wants to know what this person is all about, you can look him up on RCU, under the same name. It's not pretty, and he has not endeared himself to the community.

I'm not going to waste any more time with this person, he's not flying any jets, he's not serious, he is making up facts and figures as he goes along, there is no "we", no "staff", it's just him alone,there is not "Skunkworx Pty Limited" besides a small website, he's not an offcial Toki anything, he's not going to be flying any F-35 Vtol with Toki Fans, and...
You are not going to get four pounds of thrust out of your Toki by changing the rotor. Sorry.

He can continue on with the insults against me, who cares? Give them enough rope to hang themselves, I always say.

What I do care about is the quality of information, and his information is all nonsense. He has been told this before.

you are a fool...

everything you say here is a complete lie... you contact that dean, i'm reporting you to RCGroups admin.

go and read the posts at rcu i stand by everything said there. for each of the posts of the nay sayers i get 10 pms telling me how appreciative people are.

go ahead and "right click" the universities... i encourage you to do this... in fact please call teh director of mechanical engineering at the university.

his name is Dr. ben Cazzolato. He'd be happy to speak with you regarding your accusations and my credibility.

i posted my credentials..you posted your lame claim to fame..i.e. nothing.

please also checkout the australian securites and industry commission website for the skunkworx proof, and please approach toki and ask them about what work we are doing.

i say again, the community has hundreds of you, so i am bound to get the very same response from you as i do at rcu from some people. i encourage ppl to read the rcu things... and take it in context... like here, i posted in an attempt to provide information to DF flyers.. that they may find useful.

instead, i got an arrogant, rude, abrasive response from you Easytiger.. and what's more you start slinging at this guy Rahlberg as well!..

i provided the engineering, the calcs, the coefficients, the test data, the dyno test results, even photos of the test rig and setup.

you post nothing at all.

all you do is flame and whine.

[what_the?!]

here's your chance to prove yourself easy tiger.

i have ncluded two charts here..one from kress' website, one from nitro rc dyno tests.

please interpret the charts...taken from actual tests..and tell me what power and what revs one would expect from this engine and fan combo.

http://www.kress-jets.com/Images/720G-PChart.jpg

[what_the?!]

the hext question for you is please calculate the thrust geenrated, with a 12kt head wind, for a DF aircraft travelling at 50mph ground speed, using the rk720 and hyper 21 4 port engine, assuming that static revs achieved is 26k.

please also calaulate the efflux velocity at that speed, assuming an exit diamter of 2.58 inches.

this will prove that i had you all wrong...and i apologise for my interpretation that you were just a rude person.

the ball's in your court.

please post the results here... the next question will follow.

[what_the?!]

this next question should be easy for you coz you know so much about DFs.


please provide an estimate of the material strain, as well as stress at the shaft for the rk720, assuming that it is made of polyamide 10%, and is spinning at 35k revs.

Also, please tell me from that, what size shroud i will need to accomplish a tip clearance of 0.5mm.

if you cant type it in here, just jot it down ona piece of paper and scan it and attach as an image...that'll be fine.

cheers.

[what_the?!]

another one you wont have trouble with here.

for a surface roughness of corrugations of which the mean height is 2mm, and swept through 90 degrees, what is the % thrust lost if travelling through a distance which is 200% of the shroud length.?

please answer in terms of shroud length..which we can call Sl.

ok?

there's more to follow.

[what_the?!]

how about a really really simple one that high school students can answer... anyone reading this thread feel free to answer.


if i throw a ball up at 20 m/s.

how long will it be before i catch it..ignoring drag and surface area.

[easytiger]

Ugh. Put a fork in it, it's done already.

[easytiger]

"ll teh director of mechanical engineering at the university.

his name is Dr. ben Cazzolato. He'd be happy to speak with you regarding your accusations and my credibility."

No, that would be Prof. Colin H. Hansen, the head of the department. His email adress is right there on UAdelaide's web page if anybody wants to complain. Ben Cazzolato is a junior lecturer who was awarded his doctorate only last year. He's not head of ANYTHING.
Listen, Tim Newman...you keep posting lies after lies after lies. Do us a favor. Stay away.

I sincerely doubt that either the head of the department, or the people who administer the Sir Keith Grant, would be impressed by your words here ("you are a sand crab!")...

[easytiger]

You know, don't bother to respond. I won't. I should know better than to waste time on a troll.

The Kress rotor is not going to give me four pounds of thrust. But I can use it anyway, I've always wanted to do one of those Marcel Lahaie Mirages, and that's the rotor he specifies. Thanks so much to Mark Turner for the Toki rotor, it's just what I needed for Don to get his testing done.
He's a whiz with engines. He added a Nelson plug to one of the engines, I think. His tweaks should add a thousand RPM, I'd guess, which means a lot in ducted fan.
He pulled apart the Fantom 16, and found that, beleive it or not, it was made by Toki, also, and was actually a LESSER quality engine than the stock 18.

[what_the?!]

Colin Hansen is head of School.

clown.

easytiger..just answer the questions and all is cool...

you are trying very hard to avoid anything that prooves you know what you are talking about.

Give Colin Hansen a call then. You've obviously spent the time looking at the website.

Call him up, and ask him all about the project and me.

Heck, I'll setup a conference call if you want.

lol.

[what_the?!]

You know, don't bother to respond. I won't. I should know better than to waste time on a troll.

The Kress rotor is not going to give me four pounds of thrust. But I can use it anyway, I've always wanted to do one of those Marcel Lahaie Mirages, and that's the rotor he specifies. Thanks so much to Mark Turner for the Toki rotor, it's just what I needed for Don to get his testing done.
He's a whiz with engines. He added a Nelson plug to one of the engines, I think. His tweaks should add a thousand RPM, I'd guess, which means a lot in ducted fan.
He pulled apart the Fantom 16, and found that, beleive it or not, it was made by Toki, also, and was actually a LESSER quality engine than the stock 18.


It'll give you 4 lb alright. if i can get 3.5 lb without even trying then 4 lb + is possible.

those charts i palced here before....READ them.

I know why you havent answered any of these fundamental questions, and keep on saying that the toki wont do 4lb. It's because you CANT read those graphs.

They are simple..so is the one i posted using the Sirio.

how about the ball thrown into the air?

you are not even a DF greasemonkey..and for some reason you'd prefer to smart mouth and criticise and slag others who come in here to try and offer help and info so all can benefit.

It seems that because you didnt think of it, or work it out, then it cant be true.

BTW heres a pic of someone who already has a DF vtol that fully transitions to and from conventional flight.

he's also on our team.

[Chris True]

I think that's about enough from both sides.