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Thread: Retractable Landing Gear Drawings/Pictures

  1. #16
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    Re: Retractable Landing Gear Drawings/Pictures

    Just out of curiosity. Would it be as reliable as electric?

  2. #17
    Registered User Monty's Avatar
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    Re: Retractable Landing Gear Drawings/Pictures

    I'm at a flyin. Can't do a very good job posting. There are off the shelf modular oleos available. The air cylinders I used are COTS. I'll post more when I get back.

  3. #18
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    Re: Retractable Landing Gear Drawings/Pictures

    Hereís a retract mechanism that is very compact and simple. I donít remember where I ripped the idea from.

    Rob

    Retractable Landing Gear Drawings/Pictures-gear-down.jpgRetractable Landing Gear Drawings/Pictures-gear-up.jpg

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    Re: Retractable Landing Gear Drawings/Pictures

    Jay K.

    VT USA

  5. #20
    Registered User Monty's Avatar
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    Re: Retractable Landing Gear Drawings/Pictures

    Fox shocks makes modular oleos. The off road crowd uses them. They can be rebuilt. I would start with these before I would try to fab my own components. If nothing else you could use the internals and seals. You can put an aluminum tube on the inside to act as a stop. The idea is to start with a long shock and compress it so you are only using a 4-6 inch portion of the stroke. Make your own fittings for the top and bottom. Scissors can be incorporated into the bottom mount. Top scissor mount can use a clamp type arrangement.

    FOX / Offroad / Shocks / 2.0 Air Shock

    Bimba air cylinders are configurable: fail-safe extension/retraction springs, position switches, various mounting methods. Cad models are downloadable. Useful for many things:

    Bimba Manufacturing - Inch

    There are any number of small 12V air compressors available. Most of them are way heavier than they need to be. A Kevlar reservoir and a very small high rpm compressor could be very light weight. Plumbing can be either industrial nylon tubing, or teflon/composite braid and AN hard lines, depending on how much you want to spend.

    Just food for thought.

  6. #21
    Registered User Monty's Avatar
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    Re: Retractable Landing Gear Drawings/Pictures

    That JU88 gear is nice!

    I've always liked the F16 style gear:



    You could do this fairly easily with fox shocks and a single air cylinder. Would be a great way to go for all the guys who are working on small high performance designs that want to keep the wings clean. Just scale the design to your bird. As I said....only steal from the best!

  7. #22
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    Re: Retractable Landing Gear Drawings/Pictures

    Quote Originally Posted by RJW View Post
    Here’s a retract mechanism that is very compact and simple. I don’t remember where I ripped the idea from.

    Rob

    I started with a similar design. You need uplocks for this design and it really only lends itself to high pressure hydraulic actuation. Nice and compact with minimal mounting points though.

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    Re: Retractable Landing Gear Drawings/Pictures

    I'd like to see some of you super CAD guys work on 'retractable' aircraft --as in roadable conversion --the trickery in retractable landing gear (undercarriages elsewhere ) is rightly cause for some pride in mechanical invention and to show off as one post mentioned about model aircraft on You tube , a similar thing applies to folding bicycles and recumbent bicycles in particular --there are umpteen possible articulations and configurations and the task is to outdo the last best design in terms of packaging volume,speed of conversion, simplicity and just plain "why didn't I think of that ?" factor

    There are a couple of folding bicycles from Taiwan shown on you tube which convert so fast from the fully folded state to rideable so fast that even slowing down the video barely catches the principle -- this sort of thing really brings out the inventor and in the case of the converting aircraft really can transform (bad pun) the operation of personal air vehicles and isn't this the underlying motivation for most people on HBA ?

    Molt Taylor frequently displayed his Aerocar "transformer" going from car to airplane with manual operation and still draws a fascinated crowd at Oshkosh --just imagine how much scope there is to have a rapidly converting vehicle to aircraft and the headscratching opportunities getting everything to work .... (check out the Terrafugia transition, Brown Carplane and others like the Robin Haynes Skyblazer, Milner aircar, Switchblade and others on Roadabletimes.com for some 'inspiration' if looking for another challenge .

  9. #24
    Registered User Jay Kempf's Avatar
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    Re: Retractable Landing Gear Drawings/Pictures

    Something I have been messing with lately, just for comments and maybe some out of the box help on retraction mechanism. There is room everywhere except where the tire is and the spar for a strut and levers. Haven't found anything I am happy with to base a retract actuation design on so far. This is a bit of a bastardization of the B58 Hustler nose gear. What is nice about it is that the wheel come almost straight up. My take for a lighter weight system is a hybrid where the actual gear leg is a composite leaf spring. For scale the tire is a 6" diameter wheel with a 15.5"diameter x 6" tire. Height from wheel axle to upper pivots at housing is about 42", so pretty tall. Rails are 36" long.
    Attached Thumbnails Attached Thumbnails Retractable Landing Gear Drawings/Pictures-modular-gear-2.png   Retractable Landing Gear Drawings/Pictures-modular-gear-3.png   Retractable Landing Gear Drawings/Pictures-modular-main-1.png  

    Jay K.

    VT USA

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    Registered User Head in the clouds's Avatar
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    Re: Retractable Landing Gear Drawings/Pictures

    Quote Originally Posted by Jay Kempf View Post
    Something I have been messing with lately, just for comments and maybe some out of the box help on retraction mechanism. There is room everywhere except where the tire is and the spar for a strut and levers. Haven't found anything I am happy with to base a retract actuation design on so far. This is a bit of a bastardization of the B58 Hustler nose gear. What is nice about it is that the wheel come almost straight up. My take for a lighter weight system is a hybrid where the actual gear leg is a composite leaf spring. For scale the tire is a 6" diameter wheel with a 15.5"diameter x 6" tire. Height from wheel axle to upper pivots at housing is about 42", so pretty tall. Rails are 36" long.
    More info needed maybe. Is this for your fast acro avatar or something else? It's a neat and very compact mechanism so far but not resolved (self-locking), but would be if you drive it torsionally with the primary (short) link, and if it also travelled through more angular motion (for a taildragger) so that the primary was over-centred in relation to the applied load (a straight line through axle and primary link pin sloping beyond the vertical). The two links would have to bear against each other and the loads would be high with that close geometry. Also side loads on the knuckles with a drifting landing would be very high so they might need to be wider. If the wheel attachment was a double sided clevis it could be lighter than single sided.

    In this form locking 'up' would have to be by separate mechanism or could be a sear (as in firearm trigger mechanism) which could be tripped by first motion of the primary and so avoid a separate action for the locking, similar to gear door mechanisms.

    I can't remember enough to sketch it for you but have you had a look at the DC3 gear?

  11. #26
    Registered User Jay Kempf's Avatar
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    Re: Retractable Landing Gear Drawings/Pictures

    Quote Originally Posted by Head in the clouds View Post
    More info needed maybe. Is this for your fast acro avatar or something else? It's a neat and very compact mechanism so far but not resolved (self-locking), but would be if you drive it torsionally with the primary (short) link, and if it also travelled through more angular motion (for a taildragger) so that the primary was over-centred in relation to the applied load (a straight line through axle and primary link pin sloping beyond the vertical). The two links would have to bear against each other and the loads would be high with that close geometry. Also side loads on the knuckles with a drifting landing would be very high so they might need to be wider. If the wheel attachment was a double sided clevis it could be lighter than single sided.

    In this form locking 'up' would have to be by separate mechanism or could be a sear (as in firearm trigger mechanism) which could be tripped by first motion of the primary and so avoid a separate action for the locking, similar to gear door mechanisms.

    I can't remember enough to sketch it for you but have you had a look at the DC3 gear?
    Not for the avatar. That one has room for the locking mechanism and is more of a traditional folder. Look on Youtube for b58nose and you will see this type of gear in action. Yes there needs to be a locking mechanism but the front short link is the key to retracting I think. I have been trying to come up with a strut or a short crank and link that would bring the thing up and lock it but I can't seem to make it fit. The current way it locks is to hold the short link down and drive it to straight with the gear leg and lock it to the leg so they become one but I haven't figured that out either. There is a nose cone on that open oblong crossection to hide mechanism in.

    What this is going into is in a modular concept that I have been working up. This one is the direct drive V8 concept that I have mentioned. If anyone is dying for it I could put up a picture. Much larger than most things I look at mainly because of the engine. Have been looking at a way to do a fast cross country ship that would carry quite a bit of gear. This one isn't up to carrying mountain bikes but maybe skis and camping gear or more. Has to have tall gear and this configuration brings the gear straight up so no CG changes due to gear retraction anyway and all the parts are relatively small and straight forward. The yoke style links could be either 4130 weldments or hogged out of aluminum relatively quickly with CNC in one setup.
    Jay K.

    VT USA

  12. #27
    Registered User Head in the clouds's Avatar
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    Re: Retractable Landing Gear Drawings/Pictures

    Didnt fall asleep, been thinking, I like geometry...no solutions yet, but a couple of observations. Your bars need to be triangles of course, resolved over the spar. That gives more strongpoints - more tomorrow I have thatslow keying input bug

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    Re: Retractable Landing Gear Drawings/Pictures

    The last shown CAD drawings of the retract gear are of a four bar mechanism which strictly speaking isn't a structure and will need rigidity of the joints somehow to take any loads (or a separate triangulation not shown but still needing to lock up the pivot points ) --simplification of control systems and retract gears, wing folding etc seems to get less kudos than a very complex but mesmerizing mechanical set up -for example the intricate Ju88 wheel retract acheives the same result as the much simpler Kittyhawk system -just a bevel gear and cantilever oleo leg.

    Simplicate and add lightness is not far wrong either . By the time synchronizing and manual back up systems are added to the typical tricycle gear retract it is a candidate for future problems and likely a belly landing,bent prop, bent crank, etc as I've seen on a number of occasions (and pilots who forget the manual system exists even ) --one C402 gear up resulted in two destroyed props inc hubs,two new cranks, cowl flaps ,belly and aerials,flaps all u/s,ducts rammed full of mud and cowls plus a repaint --the pilot left the master on and drained all electrical power at his last stop. Insurance is always higher for retracts as well .

  14. #29
    Registered User Jay Kempf's Avatar
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    Re: Retractable Landing Gear Drawings/Pictures

    Quote Originally Posted by Aircar View Post
    The last shown CAD drawings of the retract gear are of a four bar mechanism which strictly speaking isn't a structure and will need rigidity of the joints somehow to take any loads (or a separate triangulation not shown but still needing to lock up the pivot points ) --simplification of control systems and retract gears, wing folding etc seems to get less kudos than a very complex but mesmerizing mechanical set up -for example the intricate Ju88 wheel retract acheives the same result as the much simpler Kittyhawk system -just a bevel gear and cantilever oleo leg.

    Simplicate and add lightness is not far wrong either . By the time synchronizing and manual back up systems are added to the typical tricycle gear retract it is a candidate for future problems and likely a belly landing,bent prop, bent crank, etc as I've seen on a number of occasions (and pilots who forget the manual system exists even ) --one C402 gear up resulted in two destroyed props inc hubs,two new cranks, cowl flaps ,belly and aerials,flaps all u/s,ducts rammed full of mud and cowls plus a repaint --the pilot left the master on and drained all electrical power at his last stop. Insurance is always higher for retracts as well .
    Wow, I see the light now. I need a retraction and locking mechanism. <forehead slap> Thanks. And I completely concur: there is no reason to try to investigate designing retractable gear because it isn't possible to keep from landing with the gear up and it adds too much complexity so no one could ever figure that out. <rolling eyes right to left>
    Jay K.

    VT USA

  15. #30
    Registered User Jay Kempf's Avatar
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    Re: Retractable Landing Gear Drawings/Pictures

    Quote Originally Posted by Head in the clouds View Post
    Didnt fall asleep, been thinking, I like geometry...no solutions yet, but a couple of observations. Your bars need to be triangles of course, resolved over the spar. That gives more strongpoints - more tomorrow I have thatslow keying input bug
    The bars with gussets at the knuckle end function as triangles. Lots of examples of that in the general aviation world like Mooney/Beech light weight stuff. Anyway, if forces are resolved in the plane of the yoke it is somewhat moot as long as the locking strategy is completed to resolve those issues. The straw man of the side view geometry is the point in this and then packaging and detail design can follow. That is how I normally proceed on these sorts of things. I build a model that is very close but not detailed to the point of deciding materials of construction but enough to look at general forces and stiffness. For the moment assume a lock in position for the general structure. For instance if the gear leg and forward link locked over center against a stop on the forward side then you need only hold the forward link locked with an aftward pointed vector at the lower knuckle to lock the entire mechanism. I am looking at a forward mechanism to move and lock the forward link right now. But moving the forward link alone will not positively lift the gear leg at the last bit of travel to a trigger lock as you have suggested. So then that drives you to looking at a way to move both links and then that is a real estate issue. Might be that I have to completely redo the whole thing but it packages so well right now if I can find a solution I can continue with the design grossly as it is currently configured.
    Jay K.

    VT USA

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