I'm looking at some of the plans/builds I'm finding online, and new to gyros, so still searching for information locations.

I'm preparing to build a rotor assembly from Crane Fly documents, and there are some differences in hole position between Crane Fly Lite and Crane Fly SFH.

Is there any sort of consensus on Delta Plate dimensions for particular blade length/weight?

Seems either this is so inflammatory that nobody will touch it or so far out in left field nobody is sure what to say?

Well I have not built a Crane Fly ..but I have build (far too many) autogyros, and have swapped delta plates of similar sizes and rotors around on many of them with no great detriment...as long as they are in the ball park.
does this help?
Chris...

Originally Posted by britinoz

Well I have not built a Crane Fly ..but I have build (far too many) autogyros, and have swapped delta plates of similar sizes and rotors around on many of them with no great detriment...as long as they are in the ball park.
does this help?
Chris...

That's extraordinarily helpful!

If they're somewhat insensitive to it I'll not get stuck into it too far.

I have built a Crane Fly and couple of others that use a triangular plate, Spyro, Lubo and my Burky.

I didn't post because I really do not know how much the size will have an effect and didn't want to embarrass myself but I would happily swap them all around. I just looked and they are different sizes with the Crane being app. 2 cm smaller (between blade mounting holes) and the other 2 are 1 cm apart.....

How 'reliable' is the 'flexibility' (can't think of the correct word) of FR4 and as such how important is the actual size???? The plate acts as a spring, Mickey explained it all in the sticky at the top of the thread but blade size, weight and RPM will all also play major parts and I honestly don't think a cm or so either way will be a show stopper.

At the time that Tom was designing the model, using a triangular FG plate to replace the the flexible flapping hinge that the original HK C30 head used was a bit of a new concept taken on by several designers in particular Rich so there could be an element of TLAR , maybe Rich would comment?????


Bolt holes around 2 mm behind the C of G is flavour of the month but once again, lots of ingredients in that particular dish and different ingredients can produce different tastes, not better or worse but different.

I know that I haven't really given you a concrete answer but I hope that it helps.

Just do the Crane like Tom designed it, remember that the blades rotate anti-clockwise (I got that bit wrong) and you will be rewarded with a great flying auto-gyro. I have a few videos of her in the air on the Tube, PaulB121090.

Paul

Thanks Paul, that's good info, I do a lot of TLAR and usually it works fine!

Appears that the minimum flexibility is pretty much limited by how easily a blade hacks off the tail or strikes.
One of the craft I looked at had a round 'backup' disk of FR4 under the rotor plate, that looked like a nice countermeasure for a soft rotor plate.

I'm concerned that a too stiff rotor plate may push the blade flapping frequency up into a range where it syncs with the rotor rpm and goes haywire.

Time to build some blades and a rotor head and get a feel for them.

nice paul

Originally Posted by Speeddog

I'm concerned that a too stiff rotor plate may push the blade flapping frequency up into a range where it syncs with the rotor rpm and goes haywire.

The flapping frequency is always at the rotor rpm. Stiffening the rotor plate only changes the phase angle. Too stiff and the advance is such that the controls become crossed, that is a nose up control will produce a nose up response and a roll response as well. Also it means that the model will respond to a gust in an off axis manner. With a totally free hinge the phase angle is 90 degrees and the controls will be "square" to the fuse. You can go with a stiffer plate if you are willing to rotate the controls to match the phase angle. You can see this in the tiny rigid rotor helicopters where the phase angle can be 45 degrees.