Wren 54 mkIII
 

Hello everyone,
I have been here reading almost daily for about 6 years now. Patiently waiting, reading, gathering as much info and knowledge as I can without causing too many disruptions. Well, I finally got myself a trainer jet (well kinda).

Anyway, I have a good friend whose been around here for a while, who is helping me get this thing ready to fly so I can get my waiver. He put it on a test stand and got it running in no time. Actually the little bugger impressed both of us. It's a propane start and we are able to start it in about 5 seconds. And the little bugger runs like a champ, super smooth.

The only problem I'm having is the motor mount is loose, and the turbine moves forward in the mount until the glo plug hits the mount. Does anyone have any ideas on how I can stop the turbine from moving? I have just sent an email to Wren asking for an answer but thought I would ask here as well. Thought about putting a piece of rubber between mount and turbine but I'm guessing here.

Thanks.

Unless you can find some Hi-Temp rubber, rubber may not work. If you are looking for only .010 - .020" Stainless shim Stock would work. Maybe even some aluminum material would work. Just depend on how sloppy it is. You might be able to pick up a new or used mount on Ebay.

I glued some 120 wet and dry strips round the case where the clamps are.

Worked for me.

I had the same thing happen to mine. You could put some type of shim under the strap as has been suggested, however once the aluminum has stretched it will probably continue to do so. I bought a new strap and put large washers under the bolts to help prevent the flat area from lifting.

Joe

If I just need a new mount then I'm ok with buying one. They are not that much.

Thanks guys.

Oh, forgot to ask another thing. One of my fuel valves was bad, so I didn't use it on the propane start. But it started without issue. Do I need to use a fuel valve on the propane start side?

ALL of the Wren 54's do that, there is not a machined stop. The trick they gave me was take a small strip of thin aluminum sheet and fold it in two. Place this around the front bow of the mount and mark (then drill) a hole where one of the cowl screws is. Screw this screw through the strip and the motor/mount-bow are now secure. Been using this trick on two 54's for 5+ years.
Greg

Aahh, I see. Easy fix. That should do the trick. Thanks a bunch. Looking forward to a lot of jet flying this season (of course waiver is first).

All good ideas above. I have used gasket paper as a spacer for the mounting straps.

While you can operate a propane start engine without the solenoid fuel valve, it is definitely not recommended.. The ECU shuts this valve whenever the engine is not actually starting, or running. This greatly reduces the chance of liquid fuel ever getting into the combustion chamber, and causing a hot start. It is actually a very valuable safety device.

Okay I'll order another one. Guess I was too excited that this did not stop me from testing the turbine. But I can see the need for one. Thanks.

It sounds like you are well on the way to success.. Wren motors have a very good reputation. What airframe are you going to put it in??

I've been running a Super Sports for years & had the slipping in the mount problem.

I just made up a small aluminium tag with a 90 deg bend in it. It slips under the mount
& the other end has a hole in it which the glow plug passes through.

Simple!

John.

I smeared high temp silicone sealant on the mount and then bolted it all up tight, that engine has always stayed in place. When an older engine without a "stop" goes back to wren for a service, they fit a bolt into the casing for me, to act as a stop against the mount.

You can line the inside of the mounting straps with any type of heat resistant material, ie, Teflon tape or a ceramic blanket material offered by BVM. Rubber would probably melt and silicone tape would degrade over time from the kero fuel. See what others may chime in here and wait for a response from Wren themselves.
Rgds,
Art ARRO

Wow, got some good ideas here. I like the idea of making a "tag" and putting it around the glo plug and mount. And I like the idea of sending it to Wren and having them place a bolt in the casing (not ready to take that on just yet).

The airframe. Well, its a ShockJet (bought it third hand as a package deal). Looks like a big high wind Kaos. Okay, now you can pick yourselves off the floor from laughing. About half the turbine guys around me laugh, the other half just say well, its got the turbine smell, that's good enough for me. I admit I laugh at myself too every time I work on it.

I have a friend that is working to get his turbine waiver too. We will be the 13th and 14th pilot in the area to have their turbine waivers. I was trying to wait him out, let him be the 13th guy but he's taking too long. I was also trying to get him to swap frames with me (he has a BTE Reaction 54). His airframe will be better with my turbine and mine for his (he has a bigger, older turbine that someone gave him, he sent it in and had it modified, it runs good).

I also bought a bigger fuel tank for this plane (92 oz), but the turbine just sips fuel on the test stand. Doubt I would want to fly it that long to empty out a 92oz tank. So will start with the 54oz tank that it came with.

I do plan to fly the snot out of this plane. Am thinking about getting another frame for the turbine. But so far this airframe has served my purpose (It was in bad shape, had to go thru it. Made some changes to it as well, did things my way. Also incorporated some mods that TBM suggested). So I did learn a lot about it and the turbine workings, and bench starting was a blessing too. It takes about 5 seconds to go from idle to full throttle. My friend has a couple of AMT Netherlands air start turbines and he swears by them. They have been flawless, and thus he has never thought about upgrading (don't fix it if it aint broke). Even he was impressed with this little Wren turbine, how easy it was to start and how well it ran.

Are you planning to use an onboard propane/butane canister or straight from the can it comes in?

If you use an offboard bottle with an on/off tap and a quick release connector then you don't need the solenoid on the gas line (but keep the one on the fuel line). This also has the added benefit that you're not flying around with a pressurised gas source on your model.

Nope, no on board propane for me, straignt from the can. Offboard all the way (learned that from this forum). Plane came with offboard propane bottle with on/off tap and a quick release connector.

I recommend poking around (researching) this forum for hints/tips regarding the ShockJet. Some guys have made mods to strengthen the wing mounting and other items to prevent inflight failures. The ShockJet is probably fine for initial turbine flights and getting your waiver but may be limited on any "wring out " flying. I've personally witnessed several inflight failures with this design. There are also several others designs: Reaction, Boomerang, Excaliber that are suitable models to step up to. Good luck with your maiden and waiver qual.
Rgds,
Art ARRO

Thanks, but I have been reading it all. The ShokJet thread has a lot of info in it regarding the wing failures and what to do. I have done the mods that I can so far. I have a friend who has a camera that I can use to check the ribs with, will do that soon. I cannot do anything about adding the plywood pieces to the spar to increase the strength (and I doubt it was ever done). And I don't like the fact the wings and fuselage was glued together with regular epoxy (instead of hysol). When I received the airframe it was loose all over. I have strengthen the fuselage all over, adding tri-stock everywhere I can, and hysol all the spots. Its tight now. The wing does cause me some concern but I'm not gonna let it stop me. I'll take it easy on the first dozen or so flights. Also know about not ever getting it into a flatspin:)

Looks like you've done all the steps to strengthen the airframe and it should be fine for your initial flights and waiver quals. You may want to check the condition of the nose and main gear mounting plates as these take a beating from landings, especially on grass fields. These can be reinforced with triangular stock and Hysoled.
Rgds,
Art ARRO

I just Googled Images for the Shock Jet. It look to be all business, no frills flying. :) I reckon you are going to have a blast with this combo..

I had to add tristock to the landing gear and nosewheel areas because they were loose. All good now. Hysol all joints I could reach. Frame is tight now. Going to run dual A123 batts for receiver and servos (had only planned to do 1 batt as per instructions but my friend kept insisting I run 2 batts) and 1 lipo for ecu. I have read the entire thread on the Shokjet and looked at several videos. Also read that it does good knife edges, 4 and 8 point rolls. Those will be tested as well as other maneuvers.

My friend flies a DV8r with a 20lb turbine (40lbs wet). He let me buddy box on this several times so I could get used to things such as turbine lag, heavy weight, etc..

You might want to use a bit bigger tank, around 65 - 70 oz to get a reasonable flight time. The Shokjet doesn't look like it drops like a brick if you run out of fuel, however due to the usually higher wing loading/weight/momentum of a jet you don't want to risk an off-runway landing so it's wise to always land with enough fuel left for a couple of go-arounds because once in a while you are going to need it! That reduces the fuel available for the flight and once you get used to letting rip, the jet engine will get through fuel quicker than you realise!