Well, when you work around helicopters, then you are accustomed to the fact, that there is big deadly mass spinning, but above your head (when on nominal rpm - Ka-26 has lower rotor main rotor blade tip at front position when at rest not much higher than my cojones are). Most helicopters are like that and it rarely happens that specific person on the ground has to do with only one type of helicopter all the time. So if such man will happen to approach a say K-MAX and he will do it from a side, well, you would not like to see the outcome.Ground crew safety? Any more unsafe than tail rotors...
Sort of ….I'm reminded that several intermeshing designs --Hiller ??--proved very, very good at hoisting hefty loads high into eg the Alps, could get onto LZs much smaller and windier than trad, long-tail designs. Snag was their flanks' 'Grim Reaper' aspect...
Did 'intermeshing' helos evolve from intermeshing 'auto-gyros' ?
Kaman synchronizes inter-meshing rotor-blades by extending rotor drive shafts all the way to the bottom of the fuselage where they meet at a pair of bevelled synchronizing gears.You need to synchronise the rotors to prevent them colliding. …
What do you mean?Transmission layout is somewhat complex as well.
Because egg-beaters are ugly.
The answer is most fundimental - too many moving parts.
From what I know, tandem rotors need to be synchronised, too, and IIRC, some accidents with the Chinook had their cause in the failure of this synchronisation (see https://aviation-safety.net/wikibase/wiki.php?id=18540 ). whereas I haven't heard this from WWII Flettner, or post-war Kaman types ...Intermeshing rotors have some issues
You need to synchronise the rotors to prevent them colliding.
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I guess, the turbine reduction gearbox is driving one of the rotorshaft, and half of the torque is transmitted to the bottom to the bevel gears to drive the other shaft.What do you mean?
Kaman K-Max mounts it’s engine and main gear box on top of the fuselage … like most other helicopters. Both main rotors are driven from that level.
Only lighter-weight synchronizing-shafts extend down to the bottom of the fuselage where they meet with a pair of bevelled synchronizing-gears.
At least one US helicopter company immediately following WW2 (forgetting at the moment) planned to use the intermeshing rotor method. I do not recall the reason it did not succeed.
Kellett is possibly the best example of yet another limitation - number of blades. I have never seen intermeshing design with more than three blades - it is possible to design, but the distance between hubs must be greater - this translates to heavier weight of transmission.Kellett XR-8 - Wikipedia
en.wikipedia.org
So you can still have six blades.Kellett is possibly the best example of yet another limitation - number of blades. I have never seen intermeshing design with more than three blades - it is possible to design, but the distance between hubs must be greater - this translates to heavier weight of transmission.
So for smaller size helicopter this layout seems to be advantageous in regard to lift capability, but if you want even more lift capability then bigger number of blades is the way to go (other wise you can reach materials limit) - like CH-53 - went from 6 to 7 blades, like Mi-26, which has 8 blades.
I have never seen intermeshing design with more than three blades - it is possible to design, but the distance between hubs must be greater - this translates to heavier weight of transmission.
No, that one (actually called V-12) was a classic side-by-side layout - at least for me - you may argue where is the border between the two - I would say if each rotor has its own dedicated gearbox then it is not a intermeshing - it may be overlapping though.Hi,
Wasn't the Mil Mi-12 using intermeshing blades? It had 5-bladed rotors.
Regards,
Henning (HoHun)
Kaman briefly experimented with 3-bladed main rotors (for a total of 6 blades) but saw no advantage and dropped the concept.So you can still have six blades.
The USAF also used the HH-43B in Vietnam as a CSAR helo*. They got 218 (18 were radial-engine powered and stayed stateside, the other 200 were turbine-powered).Sort of ….
After WW2, Flettner moved to the USA (see Operation Paper Clip) where he joined Kaman helicopters to help them design their HH-43 Husky series of inter-meshing helicopters that primarily served the USAF as fire fighters.
Reality is usually more complex:Kaman briefly experimented with 3-bladed main rotors (for a total of 6 blades) but saw no advantage and dropped the concept.
This brings us to the vast increase in complexity between 2-bladed rotors and those with more blades. As Young and Bell figured out early (early 1940s) 2-bladed rotors can be built semi-rigid with vastly fewer moving parts.
In forward flight, the retreating blade wants to lead (speed up) at exactly the same time as the advancing blade wants to lag (slow down) they balance and do not need any lead-lag hinges.
Similarly, the retreating blade wants flap downwards at the same time as the advancing blade wants to flap upwards, a single teetering hinge/bearing can allow both movements simultaneously.
Hence 2-bladed rotors only need feathering (pitch change) hinges/bearings for a parts count an entire order of magnitude less than 3-blades rotors.
It's a K-Max's running gear in a stealth body.Huh. I'd never heard of this before.
View attachment 714712
Yeah, there's a reason everyone else uses a swashplate and hinges at the rotor roots like a giant constant speed propeller.Did some work on the design via CAD a while ago and the servo flaps are definitely just making it that little extra complex when rotary airframes need less complexity. Having a rod run down the blade into a bell crank onto a flap is pretty OTT.
Not that I'm aware of.Has this type of blade control also been used on helicopters other than Kaman?