Home Built

[asra]

Hi QuojNot too far away, now the tail is nutted out! A lot to be said for making up the patterns from wood or plastic, not to mention Bunnings Aerospace fittings & hardware! ;D

[quoj]

Yeah, no worries.I just have flashbacks of something my brother and I tried to build as kids with a central, load-bearing member made of wood. Let"s just say that I sat in it "prematurely" and...well, after nearly 40 years, he still hasn"t forgotten and still mentions it from time to time! :P

[NiqueNaque]

kwaka!Looks like a nice build.One question on your radiator and its effectiveness as located.Will it work?I"d be curious to see if you have run it up to engine temp as is to see if the radiator will be able to keep up with the heat load at full bottle. It"s location behind the seat causes me some concern as I don"t think it will be effective there.Can you confirm that you"ve tried it out?I reconfigured my machine and found that the radiator located in a cowl under the engine just did not work. When I put it above the engine and 6" away from the propeller it works a treat and has been stress tested at 4600 RPM for 30 mins, it comes up to 80c and stops there.Cheers,Nic.

[asra]

Cooling - this would have to be the biggest unknown on the project. Being a jet ski engine that is designed for cold water input, I have had to considerably increase the inlet size and head outlets. I am using a high volume Davies Craig electric water-pump, designed for a V8 application! Time will tell.The radiator location may have to change like you say - the plan is to try and get as much clean air as possible trough it. Where it is now I will make up a shroud with 2 inlets positioned either side of the pilots helmet. Right in the clean air flow to try and ram as much air as possible through the radiator. I was more worried about the airflow if it has further back either up or down as it would have been in the slipstream of the seat tank.

[NiqueNaque]

http://www.asra.org.au/smf/index.php?topic=4218.0You"ll see the radiator in the left of the image.. The radiator support needs to be fixed at additional points in case the bottom part of it fails. The radiator is about 4" clear of the prop at the base, and rakes toward the front of the machine by about 15 degrees, this is to allow for forward flexing of the prop blades and for the forward deflection of the engine on its mounts between idle and full power, which is quite surprisingly large - about 5 degrees.It works very well, on the inlet side it is very cool, at the outlet it is nearly unbearably hot, especially at full bottle.I remember Richard Douglas [RD] tried what you"re suggesting - cowling, but found it didn"t work, he solved the problem by putting the radiator nearer to the prop. Cowls and the like don"t seem to work due to turbulence and the wake effect of the body in front of the cowling. Suggest you try walking parallel to a long curtain and see that there is a pressure wave up to 3 m in front of you. I"d suggest you don"t waste your time with cowling based on both my experience and that of RD.On the business of welded steel mounts, you mentioned it will probably crack. That will not be the case if it is designed to be stressed to 50 MPa or less, below this stress level steel has an infinite life against fatigue, which means a lower fatigue limit. If you weld a steel job and don"t want it to fail by cracking it may be an idea to post treat it after welding. Welding is a very hot process inflicted on a relatively cool metal, and the steel cools very rapidly after welding, so the crystals in the steel are fine and crack more easily as a result, this rapid heating and cooling also distorts the steel, you"ll know this if you"ve done a bit of welding, so welding is a process that induces stresses into the metal, to overcome this you need to relax the steel - give it a sauna in a red hot oven..Aluminium has no lower fatigue limit, any level of stress will eventually cause it to fail with fatigue. You just have to design the aluminium to a service life in keeping with the application and check it frequently to make sure there is not an accelerated failure.Hope this helps,Cheers,Nic.

[NiqueNaque]

I also had a thought about your brakes - the shimano mountain bike ones.I"d be a little concerned about their ability to last in a reliable way.What I would worry about with them is how they perform when you get up to take off speed and they get hot, potentially distort and then lock the wheel up. These brakes are not designed with any heat sinking in mind and their application is for speeds below 20km/h with light to no loading. If, as they do, one of the pads rubs and then gets hot the adhesives they use to stick the pad onto the backing may fail, then jamb up in the caliper or on the disc. I can see you doing an unexpected ground loop as a product of it, through a failure on one side of the gyro. If you "stay upright" you"ll get a nasty fright, if not, you"ll have a nasty flight and have all your beautiful work undone. Have a good think about this before you get too excited about the shimano calipers.I might suggest you try spinning your mains up to take off speed and see how the caliper performs.. being sure to restrain the gyro so there is no possibility of an accident or you hurting yourself. It may explode so do not stand in the trajectory of the caliper should it get caught up and then be ripped off - mind the hoses as well.Cheers,Nic.

[Greg Mitchell]

Kawasaki,Do you have any idea what the all up weight of your gyro will be?Mitch

[asra]

GregRoughly - just grabbed the bathroom scales and put them under each wheel - front= 20.6kg, rear LH = 40.2kg, rear RH = 40.8kg and the tail was 7.6kg = total 109.2kg currently. Remember no mast, rotor-head, rotor, pod and tail cladding, fittings, battery, pre-rotator or fluids! But looking OK at this stage. Potential pilot is currently 90kg ;DNic Thanks for your thoughts, and I agree that the radiator would be better up high close to the prop. I can get it there pretty easily if I mount it to the engine. But I am worried that it would be shaken to pieces in no time, don"t like the idea of it going through the prop! Saw where you mounted yours, but the photo is not to clear on detail - any better photos?Also agree about welded mild steel having a much better fatigue life than aluminium, but I am not a certified welder and I don"t have to cert" the aircraft!!! If I was going to anneal it, what temp and how long? Is aircooling OK after annealing or should it be quenched?Shimano brakes I totally disagree with your failure mode. The last time I rode a mtb @ 20km/h was with my 10 year old. These brakes are designed for 100Kg plus people going downhill for extended periods at speeds in excess of 50Km/h, and they have to pull you up in a totally predicable and controlled manor. I

[NiqueNaque]

http://www.asra.org.au/smf/index.php?topic=4219.0Goes a little closer to the rear of the engine.Hope this helps.Cheers,Nic.

[asra]

Found this article on the webhttp://www.eaa.org/lightplaneworld/articles/1110_thunder.aspNot sure now that there is some access to 3rd party insurance if we will get the same opportunities at our air shows?

[asra]

To close out the front of the pod I have made up a simple cone. All cardboard at this point but I am happy with the look and function. What do most people use for a wind screen - lexan or something else - what thickness and how have you attached to the pod?Been working on the rotor head and alloy engine mount today, as well as Xmas shopping. :P

[AirWolf]

Hi Tim, for your windscreen , definitely polycarbonate ( Lexan ) I used 3mm, it seems to be strong enough and is very flexible , no need to heat to form it, just wrap it around the pod and secure with small bolts. Mine is not supported on the outer edge. I have used polycarbonate on windscreens on race cars with great success in the past, it won"t crack around the mounting holes as happens with Acrylic. Cheers, Ray.

[asra]

Hi RayThanks for the information. Did you use any glue, or just bolts. I was thinking of extending some tabs on the Lexan and bolting through those, rather than making up brackets. Do you have any close up photos of how yours is mounted?How"s the BWM going? Are you close to having the first flight?Thanks for your help and have a great New Year.TimC

[AirWolf]

Hi Tim, I didn"t use any adhesive, just a moulding rubber from the Aviation section of Clark Rubber between the screen and the pod, and drilled through the Lexan. The bolts were AN-3 flat head bolts with nyloc nuts on the inside. Will try to dig up a close up photo of how it is mounted. The BMW engine is another story, still a drama with mapping the ECU (Microtec), but that should be resolved in the next day or so, I hope. Would be a nice new years present, will keep you posted.Cheers, Ray.

[AirWolf]

Tim,The photo in the Photo Gallery is the best I have of how the screen is mounted.Ray.