Wren Turbines USA

My Feedback: (39)

Guys,

Wren in England has adopted the policy of not posting on the internet. There was a excess of that in the past. I monitor this site as well as others to offer any help that I can, through the sites. However....certain things cannot be resolved through the internet.
I had to beg Wren a year ago to be allowed to have a Wren forum at the top of this page. So far it has been a positive experience. But when it turns negative as this thread has in the last several posts, guys complaining, but unwilling to send in the problem motor...there is little we can do to help. Speculate all you want, but until it is on the bench...anyone can be correct!!

The phone lines are always open to call and speak to Wren in England or feel free to call me here in the USA.

As stated earlier in the year, some changes have come about with the company. Mostly to improve efficiency within.
For those of you who are disappointed in the fact that you can no longer ring up and chat for a half hour and get caught up on all the latest.....I'm sorry.
The statements posted here regarding the "slow response". If it is that important, then you should be willing to invest in a phone call to get an immediate response. Wren receives in excess of 100 emails daily, and to sift through and answer each one accurately is next to impossible. Mike and Paul are also available on Saturdays by phone. I answer my cell from 7am till 9 pm...and later.......7 days a week.

dav.ie

My Feedback: (1)

Things have certainly changed since Sara's departure. . . . .

I spoke to Sara and Rodger directly at Jet Power to see about getting two MW 44 golds for a project of mine that is currently underwayand Sara came back with a favorable price on thetwo as she promised after consultation with the powers that be. However, shortly after Sara's and Rogers's departure, I got an email sent to me out of the blue, withdrawing the offer and saying that Sara had no authority to make the offer which surprised me to say the least.Shame, but that's the wayit goes I guess, which is a pitty as I alwasy thought Sara was "the sales person/voice" of Wren at that time.

Good engines, by all accounts, but it's just not going to be happening for my project now I would guess.

Davie

lozza1965

Its not a case of being unwilling to send back the problem motor, its been back too many times already, i think its a case of loosing all faith in a product, also sending back motors every two minutes fully insured is not cheap, this motor has been nothing but trouble since new, any other product on the market would have been replaced with new, so i can see the frustration setting in here, also the guy in questioin is without dout one of the finest engineers i know so it not a case of him being a muppett and not knowing what hes doing

lozza

dav.ie

My Feedback: (1)

Edit: Having found all my emails on the matter above, I can say that my original post above is correct without givingthe specific details of those emails and theprices I was quoted at the time by Sara on behalf of Wren.

In addition, to this I would like to sate that my post above was onlymade to highlight my own "personal first hand experience"since Sara's departure from Wren. I was however, not aware that there was so much bad blood between parties in the workplace.

Ido understand that company must still warranty and support the product, but a quote is a quote in my book, especally when more than one internal party is aware of it. Anyway, It matters not anymore as the new price I have been quoted, is not feasable for the project in hand.

Again I would like to say that Wren turbines have a great product range.and that is all I can say on that.

Forgues Research

My Feedback: (7)

For what its worth , I have done a bit of experimenting to solve the problem which is very similar to what others are experiencing here.

What I have found, the idle is too low on mine that is, and by advancing the a bit higher, the gurgling of extra fuel seems to all but gone.. Of course I will have to see if it works well in the week end at the flying field.

Roger

box55555

Someone with a positive suggestion.

Thanks Roger

siclick33

The problem with diagnosing other peoples faults over the internet is that there a variety of problems that can cause similar issues. Making alterations to idle and Accel/Decel values may mask problems rather than solving them.

There is mention of engines going back to Wren several times but no information on what was done. As such we only have half of the story which isn't really very fair on Wren. Are they getting these engines to work correctly? If so, is there any difference in the way the engines are being installed/run? If there is a recurring problem I am sure they would been keen to sort it out.

I can understand the reasons for them not wanting to post on an internet forum (probably the same reason you don't see Bob Violett here). As for the service since Sara's departure, I have had no problems. In fact I popped into their office a little while back and they couldn't have been more helpful.

Forgues Research

My Feedback: (7)

I agree in part but everytime you have a small glitch, you can't send the engine back, you need to learn about these engines otherwise you will never fly.

What I have done might mask the problem , if so, the problem will re surface I'm sure.

After reading some posts here I find a lot of people will do just that, send the engine back with the very first glitch, there goes the flying season.

Last year I sent back a turbo prop wren 44 for a gear box problem, well I lost my flying season, that's how long it took to get it back.....

Just my two cents

Roger

ron Sweeney

I thought an update on my freinds turbine problems would be of interest, and to re-cap, we have been experiencing flaming when the throttle is advanced from low to medium throttle settings. In addition we have been experiencing uncommanded shut downs prior to flying. We appeared to have resolved both issues and behind each problem there lies a tale.
I was advised by an expert to check on the fuel used and my freind admitted to changing his supplier around about the time he started experiencing problems. The different fuels were parafin to kerosene (UK terminology), don't ask me the difference but evidently there is. Following a return to his previous fuel and further advice on slowing down the pump ramp and also increasing the stability delay he had six succesful fliights. albeit with a 6 second throttle delay.
The airframe in question is a Boomerang Sprint and satisfied that the Wren SS was now performing OK, it was removed for another airframe installation and sustituted for a EVO Booster 90. This turbine had performed without trouble in a Hawk and the increase in performance over the smaller SS was eagerly anticipated. The first start was trouble free and the engine settled into a steady idle. When the Boomerang Sprint hatch was replaced the engine note changed and a few seconds later it flamed out emitting a stream of vapourized fuel. Two further starts produced the same result. Believing that the turbine was starved of air, two vents were cut in the hatch above the turbine inlet. This made no difference and the engine flamed out as soon as the hatch was replaced. The vent holes were enlarged but to no effect.
At this point the default menu was inspected and 'R' message was displayed. The advice was too alter the ramp settings and slow down the acceloration time. The same as the Wren!! This solved the problem and brought into question the airframe design??
My friend has been advised that the Boomerang Sprint airframe air inlets cannot cope with the demands of the smaller turbines without adjusting the turbine acceloration curve. I don't know if this is true and the experience of other Sprint owners would be helpful. If it is true then my freind has gone through a tormented learning curve and airframe risk. I do not wish to start knocking any body but merely wish to relay the results of our experience. We started by suspecting that the Wren SS was the likely cause of our problems and now find it wasn't. Any constructive input would be welcome. Ron Sweeney.

Ali

My Feedback: (5)

I am going to guess that your friends SS is not the only one that been fitted worldwide to a Sprint. I would have thought if it were an airframe design that I would have heard of it by now ( With over 500 sprints sold worldwide)
We used to have a SS in a demo sprint and it worked ok. I say ok, as our SS has always been a problematic turbine and even to this day it can fly 5 flights in a day with three of them ending in coughing, spluttering and flaming out, but then 2 of them going without incident ( This was how the last flying session with this turbine ended up anyway, and this is about normal)
My personal thoughts are that yes the sprint design may be an issue, but only for those turbines that are running so close to the peak of their power/ capability threshold that any disturbance/ restriction in airflow causes running issues.
Why after all are there hundreds and hundreds of sprints out there flying every weekend without issue? I am not being defensive, or aggressive in my defence of the sprint, its just that I believe the problem is not with the airframe.
Regards Al

paulflys4fun

Hi, I feel I must respond here. I fly the Sprint for Jim with the problematic super sport in it. Now when this Super sport was in Jim’s Intro is was faultless. After it was fitted into the sprint the problems you describe Ali where present. Wren where at a lose as to what the problem was, and as a result the super sports acceleration was slowed down that much it was no longer fun to fly. Jim was sick of the unreliability and the repairs to the covering on the tail plane he removed the super sport from the sprint airframe and even considered getting the turbine serviced and then sold.

Jim also has a Booster 90. This turbine has performed without fault from new. He was so impressed with the Booster he ordered a new one for the sprint so he would have no more problems. As there is a wait for a new Booster he took everything out of his Hawk including uht ect and fitted it in the Sprint. The turbine started as normal without fault and after a throttle check the Sprints hatch was fitted. The turbine was spooled up and then we got flames and smoke. This is the same thing that happened with the super sport.

As Ron has posted we cut the hatch with two 1 inch holes, but this made no difference. The turbine was slowed down as in spool up time as Wren had done with the super sport and it would run in this airframe.

This can lead to only one conclusion. That for some reason the airframe is at fault when the hatch is fitted. Both Turbines run perfectly with the hatch off.

The last thing we can try which will be today is to make a baffle as Alan has recommended. The only real difference between the Intro and the Sprint is that the fuzz on the sprint is bigger. In fact there is less air entering the intro than in the Sprint! The plan is to baffle the fuzz to make it smaller like an intro.

I must now repeat that the Super Sport in the Intro run perfectly, a real joy with great throttle response and no issues. It was not until it was fitted to the Sprint did the problems begin. The Booster also ran without fault. The booster was so impressive Jim ordered a new one, but this two would not run in the Sprint.

We write this not to knock the Sprint, we love Boomerangs. I have an XL and Intro, and Jim has a Sprint and an Elan, so all we are looking for is help with this. Nothing more nothing less.

Regards

Paul Collins

Ali

My Feedback: (5)

Hello Paul,
I do understand the details of the situation very well. Both Alan and I ( Despite neither being turbine engineers) have spent time with Jim on the phone trying to help sort the problem., and would like to se nothing more than Jim get his turbines up and running.
What I cant get me head around is the fact that there are so many Sprints around the world flying day to day on a variety of different turbines with no issue at all. The model is jig built, and has no ducting so to speak ( Basically they all have the same intakes and are built in the same way) Why then are all the Sprints out there experiencing the same issue?

BaldEagel

If we could see a pic of the instalation it may help, I don't know only guessing, but would the amount of space around the turbine and the distance to the rear efflux make a difference to the airflow, as Ali said, lots of sprints flying without problems, and two different tubines in the same airframe experiencing the same syptems, it would seem like an instaltion problem perhaps.

Just a thought, are the SS and the Booster the same dia?

Mike

Eddie P

My Feedback: (4)

Paul, thank you for your write up. As a SS owner, I have been following this thread closely. I have had nothing but *excellent performance and reliable operation* from my Wren Supersport as installed in my Tamjets A-4 for the last several years. Of course I know I'm just one of many SS owners. But I was honestly having a hard time understanding what the issue was until your write up. I still have no idea exactly (over the internet), but your additional information provides a lot of insight that this is very likely NOT just a SS problem or a Booster problem or a Boomerang problem... but something quite interesting and suitable for some intelligent detective work!

My first question is:

What components outside of the airframe and engine itself, are the same in both setups?

My one observation is:

I notice you say the issue occurs after you close the hatch. I had a Jetcat powered model in the past display the exact same behavior, usually when I closed the front canopy of the model. It only started doing it after about 10 flights, and only every second start up or so. I was at a loss at first, as the ECU shut down message just said "RPM Low". It was very disconcerting for me and I stopped flying the model and would start it up and taxi it around as I didn't trust the engine "as is", just to see if I could replicate the failure mode. I investigated fuel pump voltages at start up, run and then normal shut down and compared them to the mystery flame outs. I finally clued in that the pump was working very hard just before the flame outs. So I suspected a fuel line blockage. Turned out, I had a loose fuel line that was getting pinched, only partially, and only every so often by the hatch itself. It was an easy fix but a very frustrating learning experience.

I'm not saying this is your issue but I suspect with two independent engine makes showing similar behaviors, there is a rat in the wood pile and I suspect it's not the engine (either one).

paulflys4fun

Hi, Ali

I know you have been trying to help Jim. Jim also spoke to Alan and he advised putting the problem on here as he is as keen to understand the problem as I am sure you Jim and I am. The vents on the Intro are so small and the Wren ran perfectly, so we will try today and see if with a baffle we can solve this.

BaldEagel

We will try and get photos of the installation asap. Any ideas however silly they maybe are useful. The turbine has been moved fully forward on the mounts and fully back sticking out of the airframe with no difference noted. The Booster is very similar to the wren in size.

To be clear

The Super sport ran perfectly in the intro, and everything was transplanted from the intro into the Sprint and the problems began. We tried for more than two weeks to solve the problem, changing everything from tanks to even two ecu's. Nothing only slowing the spool up time helped. Wren where at a lose and could not identify a problem with the super sport. After blaming the super sport it was taken out the airframe.

The booster was fitted using everything from the Hawk. All the pipe work was changed. NOTHING from the wren set up was used, not even a filter or uat. Now we have the same problem with the Booster.

We can get the booster to run by changing the spool up speed from 4 sec to 5.5 sec but why should we have to??? The Booster spools up at 4 sec no problem in the Hawk, and again no problem in the sprint with the hatch off, but will not run at that with the hatch on. To get the Wren reliable in the airframe the spool up time is 6 sec.

The turbines spit flames and flame out only from no to half throttle. If the hatch is fitted at half throttle the turbines run fine. Its just the first half that’s the issue.

So yes both turbines will run!!!, but not run the way the where designed to!!!

What we want to find out is why???


Paul Collins

Ali

My Feedback: (5)

We really need a turbine engineer ( Which I am far from) to explain it properly, but to me it seems obvious that these "Hot rod" little turbines working right up at the high ends of their RPM/ Power curve are struggling to get enough air. What they require is a ducted system that will deliver enough air directly to the compressor in a relatively smooth and undisturbed manner. Ducted a bit like a DF/ EDF set up.

HarryC

My Feedback: (1)

Maybe the user has fitted a magnet to the hatch, which happens to be in a position close to the front of the engine and is interfering with the rpm sensor? Or a magnet such as inside electronic retract valves is installed next to the ECU and is causing a problem?
H.

HarryC

My Feedback: (1)

Don't know about the other "hot rods", but the Super Sport gets its thrust by a relatively high exhaust velocity rather than mass flow. Thrust is basically related to air mass and exhaust velocity, two engines can get same thrust either by lot of air mass at slow exhaust speed or small amount of air mass at high exhaust speed. The intake has to cope with the air mass going in, so an engine which is a "hot rod" will be able to use a smaller intake as it uses less air mass but accelerates the exhaust more. The larger diameter engine which uses more air but accelerates it less to get the same thrust, is the one which will require bigger intake area. For that reason, simple intake area would seem to be low down the list of suspects in this case.
Has something been done on this model that is causing disturbance to the air flow into the engine? When the hatch is off the engine will draw most air from the big open space so when the hatch goes on the air is suddenly accelerated through the intakes causing a drop in pressure at right angles - is there something loose inside that is then getting sucked inwards and causing a restriction, like a loose panel, film covering etc?
H

paulflys4fun

Hi H

The magnet idea was good, but i just checked and no there is no way that is the problem.

As for restrictions we even took the tank out, so the airframe was clear right through, but still no change. The inlet for air is both along side the tank and a second inlet next to the turbine. As i have already said we cut two 1" holes just above the front on the turbine in the hatch. This again did not help, but did give us a clear veiw of the turbine, and no obstuction was noted.

Your thoughts on the amount of air is noted, because as i have already said, the intro only has two very small intakes, and was blocked with very fine mesh and the turbine worked just fine in that.

Jim is going out with three more things to try today.

First, Make a disk to go around the turbine to fit tight on the turbine and an outside dia 20mm bigger than the turbine. This is to make the turbine similar in size to a p80.

Second, make and fit a baffle just after the compresser the same shape as the airframe, but leave a 15mm gap around the turbine.

Third, Block of the front intakes, and make the intakes the same as they where in the intro.

We will report back hopfully tonight.

Regards

Paul

Jgwright

It does seem likely that this is a repeat of the problems that have been identified before with the Boomerang design of various types. This is why Alan has suggested fitting a baffle. If you do a search on 'boomerang baffle' in the jets forum you will see that this problem has cropped up particularly when the engine is installed slightly inside the fuselage as this can cause the engine to suck in its own exhaust rather than fresh air. The baffle is a possible solution to this problem. It will be interesting to see if this is the problem.

John

Forgues Research

My Feedback: (7)

For what its worth, I have had issues with the ECU , not because of magnets, but because the battery power wires were too close to the ECU, rerouted and problem solved , of course not this problem.

Roger

Jet Doctor

Interesting![8D]

Are both turbines using Xicoy controllers(I know that the SS is Xicoy)? The reason I ask is that I had the same problem with a Kingtec 80(using Xicoy controller) in a Boomer. The only way I could solve the issue was to reroute the rpm sensor Went through the motions of removing tanks, enlarging intakes, moving turbine forward and backwards,etc.

Because there are only two possible routes to the back for wiring, we keep turbine wires together and servo wires together. After moving the RPM sensor to the "servo" side away from the turbine wiring and it worked.

I know it does not make much sense but a long shot, worth a try?

paulflys4fun

Jim has sent me install photos, but i cannot list them. If someone gives me an e-mail address i can send them for them to post!

Paul

Gaspar

Here our experience is just the inverse, we had to recommend to some owners of Intro to cut hatches to ease the suction on the engine, to avoid the engine sucking his own exhaust, but in Sprints we never had any issue. One of our local pilots have logged over 200 flights on his Sprint/M90 combo without any problem. And the M90 uses more air than a SS/G90. As I commented before, we had experienced issues with fuel, sometimes the deodorized kero is something but kero.

Gaspar

paulflys4fun

Gaspar

I am lead to belive that your merlin 90 is not running anywhere near its maxium. The ss and booster are, at least Jim has been told. Could this be why the Merlin runs well in a Sprint?

Regards

Paul