balancing a rotor is an Art, I always see my mate from averso doing it , even with the magni rotor, he his a real wizard
he never sell any fully free of vibrations rotor ... I don't understand that the polish maker could sell you a fully ballaced rotor ?

did you check your rotor head ?

Hi JM.

You could balance a rotor as well as possible, but when you take it apart for transport, it has
to be balanced again. The weight and CG, both ways ought to be okay.
I just haven't assembled it as they did, I suppose.

I'll take it apart and assemble it again in spring, at the latest when I reach 100 hours.

Cheers
Erik

Salut Erik,

Not at all Bro (at least speaking of my rotors), I have taken apart mine a couple of times and it has never started vibrating.

The point is that it is widely accepted that Gyroplane Rotor naturally vibrate .. but it is not true at all, a well balanced rotor does not shakes you stick at all.

for this you have also to use a perfectly built rotor head because sometimes vibs comes from the rotor head

With Pascal Podogorska the Averso Aviation owner, we are testing the rotors in flight on a DTA Xeeleex, and noticed that sometimes a perfectly balanced rotor starts vibrating on the gyro it was made for.. but it is really rare.

Pascal makes rotors that are exported all over the world, he has made hundreds of rotors, and he never had any issues

the point is that like many had a lot of blades in stock (around 300) , then he spends time to find among those blades comparable units in terms of weigh, centrer of gravity and twist

then he builds the rotor and statically balances it.

most of the time (and because it is an art more then a pure technique) the first flight test don't show any perceivable vibs and acceptable measured vibs using the Vibrex meter

one time out of 3 he has to perform a dynamic test and add a bit of weight at the root od the tip of the blades to make the job perfect.

the reason why it works perfect comes from the fact that the internal walls of the extrusion designed by Xavier Averso (our hernie boyett) happened to he perfect ... by pure chance ...

Pascal tried to change a little bit the internal walls of the extrusion in order to simplify production .. but it did not worked at all .. he never could get a vibration free rotor at all speeds and at all rotor rpm ..

nobody knows why ... even the DTA engineer who did a lot of calculations and simulation work did not managed to find out why ...

with his original design Pascal manages to built up to 9 meter rotor without any vibrations .. and it is cool because usually long rotor make more vibrations then small ones ..

the rotor was tested in resistance buy the german Dulv body for the DTA jyro certification .. the rotor broke at 22 tons at the root of one of the two blades .. the dulv gave a TBO of 2200 hours

the max effort on the blades at max possible RPM in flight being 7 tons we have a factor 3 margin.

the reason is that unlike Autogyro of trendak the extrusion is thicker and the rotor hub/blades attachment is perfectly designed and built.

I am happy with this rotor,

But It is just cool that there are other makers .. I would love to test this polish rotor.

cheers

jmi

You can never ger 100% vibration free rotors... the rotors can be perfect for straight and level, but shake a little in turns... or have no vibration with low fuel, but shake more with full tanks or two POB... because the tips ride higher with more weight... or the rotors tun faster etc. You can really only count on tuning rotors to not shake too much under any flight condition... it is better to have a little shake everywhere, rather than perfect in straight and level and a bad shake in a hard turn or flare, when the load increases....

just my opinion

as for me I have no opinion Murray ..

here is my mate stick in flight :

https://youtube.com/shorts/wHqCZ8peJpw?feature=share


I can't shoot the same video vith mine coz I don't have any trim, si I can't realease the stick

but belive me whatever the conditionss and rrpms I have never felt my had shaking ... I don't have anything to sell you can believe me

JM, Gyro-Tech copied the hub bar (mostly) from Averso.

And I like it very much. They have changed the hub a bit.

More work to adjust tracking (thin metal between hub and hub bar), but it probably hold a setting better.

A very happy New Year for all of us - I can hardly wait to use my newly minted license.

Cheers
Erik

Hi Erik , happy new year to you too
it would be great if you could post a couple of pictures of this rotor if you get a chance ,
cheers
G

Make sure you clean the bugs off the rotor too, dirty blades shake more.

Well done mate!

Smooth

That's excellent, really hard to get them that smooth I wish everyone out there worked at getting them that good and all the manufactures worked out their rotors this well.

I think it is easier to balance an aluminium rotor then a wooden rotor because wood is a humidity sponge

Hi if you seal the wood rotors well they are fine however what does happen in the first few hours is any moisture tends to mirgate out to the tips. So after 5-10 hours you may need to re-balance them again then after that they should be good for years (if cared for) of course if you get heaps of stone chips and don't re-paint them that can be a problem. Even then the pair of wood blades I learnt on in the gyroglider had no problems with balance after something like 13 years of use. Something you need to keep an eye on in the first few hours though. The first re-balance often would put people off them (wood rotors) as they'd probably balanced them then tracked them. If you know its likely to happen you accept it wait for it (if it happens) and then re-balance them again and you should be fine for ages.

Hey mate, 2 per rev can't be removed, but if everything else is set up well you will have very, very little shake. There are a number of factor that will increase it. Higher angle of incidence on a set of rotors increases 2/rev (as they have more drag). It also lowers rpm which will cause higher conning angle which can cause vibration also. You can get resonant frequencies between prop and rotor frequencies meeting and building (but you'd be unlucky). The most common issue on any fixed pitch rotor is out of pattern. In all likelihood if the blade manufacturer knows what they are doing they will be span wised balanced. If you have unacceptable levels of stick shake first check string line. You do this by putting the rotors between two saw horses and attach a string from the same point on one rotor to the other. The rotors should be arragned so they droop just enough in the center so the stringline passes over the teeter block. On that there should be a center punch mark if it is so much as a string width out you will be getting excess shaking.

On my wood blades I simply cut a small groove where the leading edge meets the top skin on each rotor. What can happen is the bolts holding the cluster plates can allow some movement. If you are using a lot of pre-rotation you are applying a lot of torque at that point and its possible on some rotors to get a fraction of a mm slip at this point on say 26 ft rotors that will translate to quite a bit of difference so the blades will be offset from center and the additional mass on one side will pull the mast around every revolution and hence drag the control rods and stick with it. This will give you a shake of the stick. Out of track will cause one rotor to fly higher than the other if you could watch it in flight it would make a double rotor pattern. This is felt as a vertical shake up and down in the seat. Again most manufactured blades should be all over this but its not easy. For example aluminium blades or glass blades with extruded aluminium leading edges are often warped during extrusion. The guy that made my rotors used to spend significant time bending them back to straight others would just match blades this is a particular issue with fully extruded rotors. Again they tend to match them but even if you match the last few feet you may still have some warping at different points along the rotors. For this reason composite blades are probably more consistent.

Another factor is teeter block height. The teeter bolt is meant to pass through the center of mass of the rotor in flight so this all depends on the mass of your machine, the rotor diameter and hence rpm in flight and hence the conning angle. So one set of rotors may be tuned for a given mass machine but fly it on a lighter machine and those same blades may spin slower and hence have vibration even if everything else is the same. Angle of incidence can have the same impact. This is the reason why when you pull a tight bank or sudden pull up you will get a momentary thump thump thump vibration that then settles again. You've conned the blades above the teeter block height.

Its one of the reasons I think many people have too big a rotor for their machine, there will be a optimum size for any given gyro. Remember Bensen with his Mac Engine was only flying 6 1/2 inch chord and 22ft. Wallis was flying 20 ft 6 inches and he was getting over 1000ft/min at that. Even with a 48inch prop. Mind you it only weighed 116kg empty. His high speed machine was flying 19ft rotors.

thx for this clarification Mate,

there are so many things that most of the people ignore about wooden rotors.
as a matter of fact they dont deserve their bad reputation about the moisture effect on balancing
I imagine that on the other hand those rotor must not be totally encapsulated with pain or epoxy because wood need the breathe in order to avoid water the be trapped inside the wood which could cause an internal wood decay

an other question about your 8h12 wood blades,

on the 8H12 airfoil , and especially on the slightly modified 8h12 rotor air-foils the trailing edge is thinner then the bensen wooden rotor trailing edges and in addition the trailing edge goes up at the end

how are you going the reinforce the wood on the trailing edge ?

sorry to be curious mate

[quote="Girodreamer"]thx for this clarification Mate,

there are so many things that most of the people ignore about wooden rotors.
as a matter of fact they dont deserve their bad reputation about the moisture effect on balancing
I imagine that on the other hand those rotor must not be totally encapsulated with pain or epoxy because wood need the breathe in order to avoid water the be trapped inside the wood which could cause an internal wood decay

an other question about your 8h12 wood blades,

on the 8H12 airfoil , and especially on the slightly modified 8h12 rotor air-foils the trailing edge is thinner then the bensen wooden rotor trailing edges and in addition the trailing edge goes up at the end

how are you going the reinforce the wood on the trailing edge ?

sorry to be curious mate

No worries about being curious happy to discuss wood rotors and gyros in general all day long ;) Sorry its taken so long to get back I'm back at school again (start of a new term so exhausted most afternoons at the moment).

Wood rotors are limited in terms of ability to fly in rain (although I have) It tends to erode the tips. Bensen on the float gyros used to add strips of tape to the leading edge. Initially you need to re-balance (usually only once and not always) due to moisture shifting. Having re-painted my own original wood rotors after 30 years right back to wood they are perfect inside. The root end of the underside of the blade is undercoated but not completely sealed as the steel strap there is not glued as when tracking you need to have the ability to shim under the leading or training edge. That is clamped in and painted but a small amount of moisture could potentially get both in and out. I flew my wood rotors after about 16 years idle and found I had tracking issues (trim tabs likely bent during storage or transportation) but balance was good. They definitely need more care than metal or glass blades. But once its all sorted you should get many years of use without issues. Our club glider at Grafton (where I learned) was appallingly stored for about a decade in the gap between two hangars which had a corrugated iron roof added between we slung each end of the wood rotors under metal rod bend to hang under the beams with flattened areas to support their weight. Each month we'd brush off the cobwebs give them a good inspection and go fly. They eventually become too degraded and we retired them but they were 16years old (approx) and had been used on that glider since it was built. We never had balance issues. So a well cared for set of rotors stored properly should be fine. But Australia is quite a dry place compared to Europe so mileage may well vary.

On the new blades. Our CAD files that Ivan drew up have the bottom skin wood spar and leading edge all carved (via CNC mill) out of one single piece of marine ply. Usually the wood rotors have a wood spar which is tapered at about 7 degrees back and and also tapered from a thicker root to a finer tip. The bottom skin is glued to the wood spar and the top skin which has the opposite 7 degrees over the last inch is glued to the trailing edge. Usually the wood spar is marine ply spliced (because its hard to get 10 ft lengths). We can get marine ply up to 12 ft long so our blades will have no splices in this part. Because we can machine the shape accurately we will be incorportating the bottom skin into the whole bottom of the rotor. To maintain the shape (wood rotors usually have bottom and top skin flat to the reflex at the rear) pockets are going to be carved out of the top rear surface. This ends in a small triangular section where the ribs meet the trailing edge. This will give a large surface for the top skin (3mm marine ply skin) to be glued onto. We will be milling out of MDF board a top mould to help hold the top skin to the correct shape for the bottom half of the rotor. The trailing edge will still be quite thin as it is on normal wood rotors. The top skin of my wood rotors ends about 25mm from the trailing edge which is only 3mm at its thickest. This has a reflex carved into the bottom skin 25mm wide down to 1 ply (1mm) at the trailing edge. The N8H-12 blades will be similar thickness at the rear. Of course we will experiment which short sections first to make sure it can cave at the level of precision we need but we think it will be fine. Additional (actually first) we will cave out the gap for the steel spar which will be water jet cut to size and have all the holes cut. Leaving only the counter sinking of holes.

My original idea was just to make the leading edge and wood spar as one piece and just make the construction of normal wood rotors easier. If we can pull this off we may gain some greater efficiency - a little more lift too. Basically if it works we'll make the files available for anyone with access to the machines. We estimate between $400-$500 AU to build a set of rotors suitable for a single seat gyro. We have zero desire to sell any we just want a viable alternative for someone without the level of wood working skills required. Wood rotors are not brain surgery but I was lucky in that Ivan (who I build my original rotors with) was a cabinet maker by trade. We therefore had access to large table saws and a rotary molder. We had cutters made for the leading edge of our rotors as a few of us wanted to build wood rotors. So Ivan and I made about 5 sets for ourselves and others at that time. We had two blade benches made so when gluing any give part we'd do both together in the hope that any moisture levels at any give stage would be the same for each rotor. That may not have made any difference but Ivan lived a 20 minute train ride from me so I'd pop over for a few days and we'd process the parts together and then glue and clamp wait overnight process the next step and then glue and clamp wait another night. We were building a set of rotors in about a week. We worked out about 20 hours of labor for each set from start to finish. However that was with two of us working which helped enormously. These should be significantly shorter time to make. Although lots of farting about to work out exactly what to do and how to do it. I spend a whole day installing an Linux CNC on a computer that didn't want to take the OS for example. We'll make 4 sets (two each initially) and have the ability to then quickly build more if someone else near us really wants to do some but likely we'll test these fully and it will give me rotors for my current powered gyro (I will also use my old metal blades too) and for my next gyro - which will be build light to potentially be electric (if the batteries improve enough). That will be a sub 100kg gyro empty weight.

I plan on staining then clear coating my set just to shock other gyro blokes when they see them ;) When I was flying my wood rotors people would ask what they were made of they were nicely painted and look like glass blades. You'd see them visibly shudder when you told them "wood". I loved that.

the fiberglass rotors are also limited in terms of ability to fly in rain, even with my aluminium rotor I have rarely been caught under the rain
first of all I don't fly when it is raining ... I have the choice .. I am not forced to fly ... even when a collective flight has been planned by the hangar fellows I always give up when the conditions are not perfect.

when I have the slightest issue with the gyro, when I don't feel good, or when I estimate that the weather conditions are beyond my personal skills.. I give up.. go to the bar and have a couple of coffees and start maintaining my bird ... I have often been bullied for this but I don't mind ..

in addition we have really reliable applications which makes it possible to see where it is raining
lastly when one is flying, one clearly see the black "fibres" , like female black hair which shows that it is locally raining ...it is easy to go around the places where it is raining.

therefore even when one has to go across a rainy zone in order to reach his airstrip, in does not last long

what do you mean by undercoated but not completely sealed ?

when you say the ability to shim under the leading or trailing edge , do you mean adding small washers btw the "cube" and the hub bar to increase the angle of attack of one blade and reduce the angle of attack of the opposite blade @ the same time?

I don't see the relation with the fact that the steel strap is glued or not ?

I don't really visualise the steel strap in fact ?

do you shim the blades independently for the tracking ?

I mean I am shimming the hub bar .. and it has an action on the two blades at the same time in fact .. i am not saying that it is what it is best to do, it is just a question .

I stop there my comments and questions about all you have explain us for a while ... I will go on after we have talk about my 3lasts questions ..

I think your message is so dense that it will take me months to ask you all the questions

Giro... when you paint wood. unless just using clear because you want to see the grain... you first seal it with 'undercoat' paint... (that gray or white paint)... then you let that dry and put the 'top coat' on (which is usually the color... then maybe clear last of all. I think Cam is saying that it is bst not to completely finish and seal the tips right away, so ant moisture can leave the tips from centrifugal force. Maybe after a few years or many dry flights, the tips can be sealed. I could be wrong... Cameron can correct me.

I believe he is talking of the metal plates where the hub bar straps meet the wood rotor blade... where the hub bar bolts attach the blade to the bar. If someone finishes the wood rotors, then immediately bond on the steel to the wood... it might be necessary to shim or shape under the steel plate which will be more difficult if the steel is glues to the wood. I believe he is saying not to initially bond the steel to the wood... until the rotors have been test flown and are close to perfect... then bond on the steel... again... Cameron can correct me if I am wrong