Kaman H-43 Huskie

[ELGEE525]

Just a thought--After having a blast inside my house with the Hirobo XRBS,
I was wondering if anybody has given any consideration to the Huskie?
After doing a little thinking and sketching, it could even be done with one motor and three pinions due to the angle at the bottom of the rotor shafts.
It might be fun to experiment using existing rotor setups i.e. cyclic , or even
mounting the motor on a gimble and tilting the whole thing.Comments?
I think I'll take a couple of my Aerohawks apart and play with this. They have been crashed so much they deserve a new lease on life !!
ElGee

[desmo]

Italeri make a plastic kit of this bird and from memory when I built one ( 20 years ago ) It is quite big and already has a gear box of sorts for synching the two blades. It might start you off on a solution for the building one from scratch

It is well worth a look after all the success converting plastic helis to rc, my only concern would be controlling the thing with 4 servos and two swash plates requiring synchronisation.

Good luck

[ELGEE525]

Hi Desmo,
I think since the two sets of blades would be geared together,and the control inputs would have to be the same for both sets,one set of servos would work using linkage to connect the two swash plates-- I found one of the old plastic kits on E-bay and bought it last night as a starting point, mainly for body deminsions. It's 32nd scale so just about perfect for micro heli hardware- I 'm really jazzed about this !! Nothing ventured,nothing gained !! NO tail rotor to worry about !!
ElGee

[Geoffrey109]

Interesting Project....

[IAD]

For what it's worth, I tried this some time ago... The catch is, if you make 'micro-scale' the blades have to be wider than the full-scale version, and thus there is 'undesirable' interaction between the TEs of one pair of blades, and the hub of the others. (Where undesirable = contact, such that the contacting blades tend to break.)

I will also mention that worm-gears work well, if inefficiently, for the blade-sync/gearing. Worm-gear of proper pitch between the two shafts, with an 18-tooth pinion-sized gear on each shaft, and presto, syncronized rotors, with 18:1 gear-ratio.

~Luke

[ELGEE525]

Hi Luke-
I think I've got an answer for the gear train by using the beveled tail rotor gears from a Shogun- I think the Huskie has about a 18-20 degree separation and by increasing
it to 30 degrees I might get some more working space for the blades- provided they still provide enough lift at that angle- and still, they would provide mechanical separation as they would be driven off a single center pinion-again, one of the beveled tail rotor gears(Three beveled gears-one as a pinion). Rotor shaft length is another option for separation-- I haven't thought out that too much yet as flex gets involved. how far did you get ?
I still might try a gimble set-up for the entire rotor system, it would only take two servos and still give 360 degrees of cyclic- but there might be problems with aerodynamics in that scenario. Hey- all it can do is crash- and I've got that down pat !!!!!! I thought I was going to have problems with finding matching blades of opposite rotation, but my Hirobo XRB solves that problem.I've got several small brushless motors so I think I have the horsepower problem solved.If none of this works, I'll just use the entire Hirobo drivetrain and have a 'different' kind of Huskie. It's probably the route Kaman shuold have taken anyway- but ,they were pioneers !!
Thanks for the input-I never thought about the blade width problem !! You saved me some headaches !!!
Larry G.

[IAD]

Shaft length MUST be identical. Otherwise, when the rotor that was passing over cycles around, and starts passing under.... You get the picture. Also, don't forget that the larger the seperation angle, the less lift is provided.

DON'T try to use the XRB rotors..! Just my opinion, but here's why: The top and bottom rotors are definitely NOT the same pitch! (Coaxial rotors must have steeper pitch on the bottom rotor.)

I don't have any pictures, but I had a full set of geared shafts, rotor blades, but no control system. Speed-300, driving flybarless 18" rotors, with an 18:1 ratio. Under normal running, I had 1" of clearance between the top of the hub and the passing blade. More clearance could have been attained by making the shafts longer, but that isn't really a solution, because the blade-flap amplitude is greater further out on the blade, thus simply increasing the probability of hub/blade interaction. (My best attempt used 'stalked' blades, with a long thin area where the blade would pass over the opposing hub.) In theory, an offset-hinged head, with the hinges outboard of the point where the hubs cross would eliminate some of the problems. (Never tried that, though.)

Getting a good gear-ratio with the bevel gears will be difficult... After reading how inefficient the worms are, I tried coming up with something like that, but never got very far.

In re: Kaman... I live rather close to Kaman Aerospace, and have seen their K-MAX heavy-lift helo fly overhead quite often. I disagree that the coax. is supierior... At full-scale sizes, the intermeshing is a LOT easier to control/design, with only minimal efficiency loss. (Also, it seems to have stronger yaw control. Differential fore-aft cyclic, if I'm not mistaken.)

~Luke

[ELGEE525]

Hi Luke,
Iwas just going to use the blades from the Xrb, not the rotor system. Hinged flapping blades might be the answer-good call---so it will take making a longer root on the blade, like the old Siskorski type blade atachment on the H-19. Mabey using a programmable radio would allow a height differential on the two masts,only enough for clearances though.It would mean using four servos and two independant swash plates-and some major mixing to achieve the same results from both sets. This is getting too involved !! The gear ratio using three identical bevel gears would be 1 to 1, so using a geared motor could offset the rpm problem,and the torque problem-just need to know what the head speed would need to be- probably close to what most minis fly at.Collective would seem out of the question due to space and control requirements ,but then again, using a single slider to control both swash plates at the same time might work-using one servo-- it will be a fun expirament -might not ever work in this scale-but worth a try.
Larry

[IAD]

I would slave in some 'outward' left/right cyclic in both heads, so that the blades tend to deflect away from the hubs. (Thus, the swashplates would always be angled away from the centerline.)

There is no physical way of getting different height shafts, if you make one longer, granted its blades now have more clearance, but the other set has less. So, nothing gained... Possibly something lost. (Like a pair of blades! :eek: )

~Luke