hi all
i need some advice with my wren 54, the problem i have is it doesnt produce much power, to give you an idea , it just about gets my boomerang out of our field (i fly from the bickley club), it then requires a nice shallow climbout but does pick up speed for a half decent flight..
first the history.... it began life in a helicopter which ran realy well, ample power for the heli.... now, ive taken it from the heli and put it into the boomerang, before doing this i spoke to wren about any changes, to which they advised a PT wheel change and a cone along with some settings changed in the ecu... i sent it to wren and after looking at it they suggested just adding the tail cone and see how it goes. the ecu settings are now at, max speed 160.000... max temp 850. acceleration 7 , , deceleration 7... . its been running ok but way down on power..... would it be the PT wheel being different?, are they different?, if so would anyone be willing to change it for me, i dont think wren were too interested due to its history., it was put together by an undesirable to put it politely...

comments please guys

thanks

dean

Does it actually get to 160,000 rpm?
Was it running OK after it came back from Wren?

Your best bet would be to send it to Wren and have them fix it. Regardless of its history it is in Wren's best interest to have you as a satisfied customer and to not have a poor running example of their product in use.

Joe

What do you mean by PT? If by PT you mean power turbine then that shouldn't be left on the engine in a turbojet installation. The power turbine is the turbine wheel of the gearbox that sits behind the 'gas generator' (i.e. the engine) in turboshaft/turboprop applications.

I'm guessing you are just talking about the turbine wheel, in which case I can't see them being that different (although I may be wrong)?

As joeflyer says. What are the actual ECU readings at full power?

i believe also that theTP wheel has less thrust in the first place.
.
i bet you have temps around 450 degrees?.

This engine has a gas-generator turbine wheel which doesn't produce a lot of thrust. It was originally the first stage of a helicopter, as Dean has said.

The parts for the engine were sold in 2003 to a guy called Neil Key who was producing helicopter engines. He had bought a load of parts from Dick Wallinger who was a friend of ours and was involved with the first Wren helicopter in 1999. Dick had decided to make heli engines and bought some parts from us whilst sourcing others himself, but then he went onto other projects and sold the turbine heli stuff to Neil.

The engine would have more power if the gas-gen wheel was changed for a thrust one. Dean sent the engine to us recently but when the guys saw it was in one of Neil's engine cases, with his red FOD screen on there, they declined to work on it. We don't know what's inside it but we do know that not all the parts are genuine Wren ones. We don't know how well it was built, it's an old engine and we suspect that it would need a lot of new parts to bring it up to a standard where we would be prepared to give a warranty on the work we'd done, and that would be almost as costly as a new engine. So we checked the ECU and changed some settings, we put a tailcone in the box with the engine (gasgen engines don't have one) and returned it to Dean.

If there is a homebuilder out there with time to spare who has a thrust turbine wheel, then perhaps they would be able to help.

BTW, reference Dean's comment about an "undesirable" - Neil traded as Turbine Technics and caused a lot of problems to a lot of people by taking money for engines and not providing them. We supplied parts to him from April 03 until early 04 when we started to hear complaints from his unhappy customers and stopped dealing with him.

Sara Parish
Wren Turbines

[reason for edit:typo]

Not sure what a PT wheel is but all you should have is a compressor at the front and a turbine wheel at the back. If these are the same parts that are on a normal turbojet and if it is reaching 160,000 rpm there should be around 14 lbs of thrust comming out the back end. Can you post a pic of the front and back end of the turbine

They are not the same. It's got a gas generator wheel designed for a heli or turbo prop. It needs the thrust wheel. If the temps are 450 deg as Sandor suggests then I would be surprised if you were getting 10lb out that engine even if it has the later 14lb compressor.

Jason

I believe the thrust motor has a turbine wheel with 21 blades and the gas gen has 19.

If you have a WREN 54 with 12-14lbs of thrust it will fly very well if you Boomerang is the Intro. My flew with a RAM 500 (12lb) at 5700ft MSL, performance was very satisfactory. Takeoff perforance improved about 15% when I changed to WREN SS engine.

hi all
firstly thanks for the replys, sorry about my terminology but by PT wheel , i mean the turbine wheel at the back..ive just counted the blades and it has 19 . so this is my problem.

jason
you are right when you say im lucky to be getting 10 from it...... unfortunately im stuck with it until i can find someone with some hands on knowledge with the wrens...

can anyone shed any light on the job to change it. are there diagrams or videos etc to guide me through it? anything would help guys

thanks again


dean

This engine can be built from a kit - perhaps you can get a copy of the assembly instructions from Wren (a pdf file?). But replacing the turbine wheel means re-balancing the wheel/shaft, so you'll have to find someone who can do that (since Wren declined to work on it...)

Hi 3dean

Here in Australia our Simjet dealer, Kyle Communications, has balancers and expertise to service engines. Maybe contact Mark Kyle and see if he will have a look at your engine. I'm shure you could purchase a pre-machined thrust turbine wheel and maybe send it all to Mark for fitting and balancing.

Just a thought.

Kind Regards, Craig Dyer

We are happy to re-balance a shaft assembly - in fact I think that if the engine was taken apart and only the shaft assembly was sent to us the guys might be prepared to change the wheel as well. We often do shaft assembly balancing for homebuilders and people with kit-built engines who do their own repairs. I can send Dean a copy of the kit instructions which show how to build the engine.

Sara Parish
Wren Turbines

It amazes me that the difference between 19 and 21 blades would make that amount of difference..... Just goes to show how little I know

Dennis

The NGV on the gas gen is also different, as well as the blade angle on the turbine wheel.

Yes, all sorts of things affect thrust, it's not really the number of blades! The early Wren MW54s only put out about 11-12 pounds and it was a change of compressor plus a few extra tweaks which took them to 14.

The wheels are designed for different purposes, the gas-generator has a more rounded, scoop-like shape compared with the flatter thrust blade and is intended to generate the gases needed to power a second stage.

Sara Parish
Wren Turbines