RFguy Posted October 26, 2020 Share Posted October 26, 2020 I would think just pitch control would meet 99% of your requirements. takeoff- set fine, climb - set medium. cruise- set coarse. and leave it there.....all the way until after landing and shutdown if you like. maybe set to medium for circuit and landing. I see CS as a huge additional complication and complexity, especially for limited returns like this example. Of course, there are good reasons to have CS for specific missions if they warrant it..wider envelopes, engines you want to keep within specific bounds... glen Link to comment Share on other sites More sharing options...
skippydiesel Posted October 26, 2020 Author Share Posted October 26, 2020 1 hour ago, facthunter said: CS is a different matter where you need something doing the work of a governor. You asked about IFA. That's why I replied.. .. Nev Sorry I miss understood - would I be correct in saying you are not supporting electric IFA as an unnecessary compilation of what should be a simple mechanism? If my statement above is correct - I agree with you. I guess I am looking at the possibilities of two in flight adjustable concepts - one using a CS the other purely adjusted by the pilot, IFA, as flight conditions present themselves. I started only considering CS but with my investigation of Kasper I seem to have opened up an alternative possibility IFA. Link to comment Share on other sites More sharing options...
skippydiesel Posted October 30, 2020 Author Share Posted October 30, 2020 Small tangential topic drift: Just out of curiosity I have been finding out about step/stepper motors - they are truly an amazing bit of technology. The motor itself is quite simple, unfortunately the drive/control is a tad complex (for me). Cant understand why a suitable step motor, attached to a worm drive or jack screw, could not be used in Rotax (hollow offset propeller shaft) type engines for in flight prop adjustment. Mounted on the top of the crankcase and driving through the hollow shaft to the blade pitch mechanism in the hub. This must be second only to a manual adjust system in simplicity and potential light weight. As for the drive/control - if I understand the system at all (?) It can be very small and light and several layers of redundancy can quite easily be incorporated. I suspect that the variose black boxes" supplied with electric constant speed propeller systems, are in fact, a step drive linked to a simple RPM pick up - driving a step motor located in the prop hub. It seems nuts to me to have the motor in the hub, usually hung out front, where its weight is having a greater impact on W&B and where it is subject to rotational loads and its "connection" with the driver & power supply must go through a slip ring arrangement (potential failure point). I will be interested to get your feed back on this. Link to comment Share on other sites More sharing options...
RFguy Posted October 30, 2020 Share Posted October 30, 2020 yes, I know about stepper motors..... what holding torque is required for the pitch control ? Link to comment Share on other sites More sharing options...
kasper Posted October 30, 2020 Share Posted October 30, 2020 18 minutes ago, RFguy said: yes, I know about stepper motors..... what holding torque is required for the pitch control ? If you're worried about standing load on the remote motor just do what we did with electric movable hang points for flexwings - use a linear actuator. They are generally rated at 1500N force, have ranged of linear motion from around 50mm to 200mm and weigh next to nothing. The eletric in flight hang point adjuster I had on the Raven cost under 50 pounds UK in parts (including the two machined mounts and all switiching and hang position display in the dash) and installed added under 2kg to the airframe. Gave infinite position change between the two stops (not stepped) and that set up moved 55kg of wing mass whilst in flight lifting 450kg of aircraft all on the standard nylon frame collar. A quick ebay search throws up 12v linear actuators for under $15 so some of the componetry is inexpensive for manual adjust - its the electronics and sensors to link manifold pressure to the actuator to make it CS thats tricky. If you had a variable prop hub with a slip ring on the blades in the hub remote back to a linear actuator mounted to the engine gearbox you have removed much of the mass on prop hub issue and have removed roational electric components and this would be relatively easy to do as a manual adjust in flight. Just a thought. Link to comment Share on other sites More sharing options...
RFguy Posted October 30, 2020 Share Posted October 30, 2020 (edited) Good comments Kasper . really depends on what it needs- pull and push rod (linear actuator like) or rotation. All comes down to rotation or linear motion required. I would have thought it would be a linear motion requirement. For linear actuators, these are usually screws on shafts driven by continuous or stepper motors. The bigger ones are ball screws, the smaller ones are ACME leadscrews. You want the ball screws. reliable. They can take the form of a pushrod output, or a carriage on linear track. Or a ram using hydraulic fluid. It's not a big pump you need, pressures are low. For rotation , you dont need speed , and probably lots of torque, so a stepper or brushless motor driving a gearbox is usually what is used. They are supplied fully integrated. As usually , go overboard on size to reduce failure likelihood. If a gearbox represents a problem for vibration induced failure modes, then TWO through shaft (double ended shaft) steppers can be used, they can have cascaded shafts. The motor will not jam, but if you blow a winding or a driver, the other motor will do the job. OR, go oversized. I'd be surprised if a reasonable sized practically sized motor would have enough torque (without gearbox). if the mechanism under power relaxes in one direction, and is fairly well damped, then you might only need a pull shaft or cable.... -glen Edited October 30, 2020 by RFguy Link to comment Share on other sites More sharing options...
Kyle Communications Posted October 30, 2020 Share Posted October 30, 2020 From what I have seen the drive motors are just DC motors in most CS units If you are wanting proper positioning control you need a closed loop stepper or a proper servo with built in encoder. For a IFA a linear actuator would be fine through the gearbox in reality thats just a DC motor driving a threaded rod or some Verier cable adjuster...KISS is what I like Link to comment Share on other sites More sharing options...
kasper Posted October 30, 2020 Share Posted October 30, 2020 (edited) 25 minutes ago, Kyle Communications said: From what I have seen the drive motors are just DC motors in most CS units If you are wanting proper positioning control you need a closed loop stepper or a proper servo with built in encoder. For a IFA a linear actuator would be fine through the gearbox in reality thats just a DC motor driving a threaded rod or some Verier cable adjuster...KISS is what I like Exactly. And if the deforming blade variable pitch blades system in IVOProp were effective then it would be a relatively simple mod to remove the spinning motor, remove the electric slip rings and the rod mounted brushes and insulator plates and use a push/pull rod through the gearbox with a suitable turned collar on a sealed ball bearing ... or just buy a non-inflight and modify to make it in flight adjust - same blades and cheaper as youre not throwing away bits. By doing this you would remove rotational mass on your prop shaft, remove most of the failure points on the electrics (all the rotating sliding bits) - win win really. see pic below for the IFV setup to see which bits you would remove and the single gold slip collar that would need to be manufactured for the dn of the through box pushrod. Edited October 30, 2020 by kasper Link to comment Share on other sites More sharing options...
RFguy Posted October 30, 2020 Share Posted October 30, 2020 Kasper Good cross section. just a note - "By doing this you would remove rotational mass on your prop shaft," NB : the rotational INERTIA from stuff in the spinner may be low compared to the blades. How low, I am not sure, would need to weigh the pieces, and distance from centre. There are certainly rotational inertia limit numbers for engines and gearboxes. Link to comment Share on other sites More sharing options...
RFguy Posted October 30, 2020 Share Posted October 30, 2020 (edited) An excellent read about propellers, vibrations, resonances, slip, pulses etc etc especially Fig3..... The Jabiru 4 cyl motor also gets a mention. (mostly translated- some graphics not) Colloques2016BuiattiHELICE.fr.en.pdf Edited October 30, 2020 by RFguy 1 Link to comment Share on other sites More sharing options...
skippydiesel Posted October 30, 2020 Author Share Posted October 30, 2020 Seems to me we ae all on the "same page". I figure that the important & heavy bits of a CS/IFA are the hub and system for holding a blade root securely. A blade root that must be able to rotate/move through a very small arc. Once this has been sorted, a cam type mechanism is needed to make the movements. The movements must be identical on all blades, fully controlled and repeatable. I looked at the linear actuators but felt the step motor had inherently & potentially better "vernier" type control. What I have in mind is something like a rack & pinion set up (which is a bit like a linear actuator anyhow). The deforming blade concept is certainly KISS but I must confess it doesnt quit grab my attention. Link to comment Share on other sites More sharing options...
RFguy Posted October 30, 2020 Share Posted October 30, 2020 (edited) A stepper usually drives a screw with the travelling 'nut', so converts rotational motion to linear motion, according to the screw "Lead". My actuators for heavy lift robots have abotu 2mm pitch, my PnP robots have about 35mm pitch on the screw. torque increases as PI/screw lead. Rack and pinion? naa you've really just built a poor linear actuator, compared to a ball screw. The only reason to go R&P is if the travel distance is LONG- like meters. That is what is used on large CNC routers.... up to about 200 cm you'd use a linear actuator made from a screw . Edited October 30, 2020 by RFguy 1 Link to comment Share on other sites More sharing options...
Kyle Communications Posted October 30, 2020 Share Posted October 30, 2020 Linear actuator would be better than any stepper for the job. More torque because the worm drive into the main adjustment rod gives the better mechanical advantage. Most good actuators have a pulse counter in them so you can position them the cheaper ones just use a pot for a voltage but thats no where near as accurate as a opto or hall effect pulse generator Link to comment Share on other sites More sharing options...
RFguy Posted October 30, 2020 Share Posted October 30, 2020 Agreed Mark. Holding power (for max torque) is substantial for a decent sized NEMA 34... Steppers direct are good for SPEED. otherwise since you do not need to move the pitch from 0 to 100% in milliseconds, use a linear actuator and use a tiny wheeny little stepper motor and low pitch ball screw. Link to comment Share on other sites More sharing options...
skippydiesel Posted October 30, 2020 Author Share Posted October 30, 2020 Okay! okay1 a stepper driving a linear actuator with a pitch ball screw - seems to meet all the criteria - What will you control it with ? Something like the CS black box with the option to have pre programmed pitch points for TO, Climb, HS Cruise & Econo Cruise, that can be switched to manual for "playing with" the pitch and may be an auto feather function for the day the noise stops. Link to comment Share on other sites More sharing options...
RFguy Posted October 30, 2020 Share Posted October 30, 2020 just any industrial stepper motor controller,with up/down and speed inputs. etc . No Arduinos here. it will have end stops on the actuator so that the controller knows where 0 and 100% is, and because it is a stepper, it just counts the pulses. And if the stepper motor is well sized, it will NEVER miss a step, so it will be fine open loop. just find your actuated hub. Link to comment Share on other sites More sharing options...
skippydiesel Posted October 30, 2020 Author Share Posted October 30, 2020 Sounds like an electronically actuated IFA - no point when you can do it with a simple Borden cable & some clever leverage - why not go the full CS by having an RPM input/response?? Link to comment Share on other sites More sharing options...
RFguy Posted October 30, 2020 Share Posted October 30, 2020 sure. we are not arguing with you ! I'll be interested to know what you find in IFAs. Certainly for Rotax, a huge assortment of props. Link to comment Share on other sites More sharing options...
skippydiesel Posted October 30, 2020 Author Share Posted October 30, 2020 I recon clever chappies like a certain RF Guy & Kyle Comms could could easily design a CS prop,with mostly off the shelf stuff - might be better to get an existing proven hub & blade set up (no point in reinventing the wheel ha ha) Link to comment Share on other sites More sharing options...
Kiwi Posted October 30, 2020 Share Posted October 30, 2020 Flybox Propeller regulator PR1-P man_PR1P_eng_rev31_45.pdf Link to comment Share on other sites More sharing options...
Kyle Communications Posted October 30, 2020 Share Posted October 30, 2020 Not as easy as it sounds Skippy...the hardware is a piece of cake no issue...the software?..well thats a whole world of hurt...Just ask Bolly Link to comment Share on other sites More sharing options...
RFguy Posted October 30, 2020 Share Posted October 30, 2020 and that it's software for mechancial thinking people.... they make rookie mistakes on scope and spec when contracting a software guy to do it.... and a software guy is not always useful if he doesnt have a firm grasp of the problem / function. The software person for this job (CS) has to have a good knowledge of feedback control systems and feedback control loop / stability theory, or implementation of a feedback loop person's ideas. and of course the software guy who isnt a feedback system person doesnt really know when it is borderline stable or not, without the designers writing a whole load of tests around it. And they only write the suitable system test spec IF they understand the potential problems !!! So, it takes a special blend to get a good product. Luckily, the system , if the response is slow enough, IE overdamped response, can be modelled pretty well as a 2nd order system, easy peasy. Needs to have checks and balances in case it gets a SENSOR error.... That's another common royal F.U. -glen. Link to comment Share on other sites More sharing options...
skippydiesel Posted October 30, 2020 Author Share Posted October 30, 2020 There you go then - a pair of geniuses - I can see it now $4000 pro & hub $400 CS control system - use at your own risk. Ill be your test pilot ( no brain, no pain) Link to comment Share on other sites More sharing options...
skippydiesel Posted October 30, 2020 Author Share Posted October 30, 2020 12 hours ago, Kiwi said: Flybox Propeller regulator PR1-P man_PR1P_eng_rev31_45.pdf 799.08 kB · 4 downloads Interesting - the magic black box for about $600 AU - seems like a good deal - so now we just need a good deal on a safe/reliable prop/hub set up , Kyle & RF's best selection for the linear actuator - an off the shelf hall effect RPM sensor, a little bit of machining (I can probably arrange that) and we have ourselves a CS prop for a smidgeon of the big boy price. Link to comment Share on other sites More sharing options...
Kyle Communications Posted October 31, 2020 Share Posted October 31, 2020 Glenn is spot on about software developers..some can only relate to a computer monitor others have real world experience that they then can use to program the project. They are the really smart ones. The guy we use for the products I designed all the hardware for at work is unbelievably good. I get down and bow to him. he is good with digital stuff but analogue not so much but in a previous life he was a biochemist. Just the sort of person you want to write algorithums to measure salt using your electrode specific design. The big thing is I understand him and he understands me..thats why our product is the best on the market. The big issue with the CS unit is the hardware design of the prop hub...sounds easy but not so much at all. The forces and stresses to make stuff move at 2300rpm and multiple blades...yeah..better engineers than me do that stuff. I know my limitations 🙂 1 Link to comment Share on other sites More sharing options...
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