sprung oleos

[kenking-King Design]

Made these for a fellow modeller. If anyone else wants some or similar let me know.

[Former Member]

[This posting has been removed]

[kenking-King Design]

Thanks Percy, I thought so too but no responses so far. Pity, because I enjoyed making them and more importantly, my client was very pleased with them. I chose the springs after much deliberation, to give 1/4" compression on the ground under the model's weight, leaving another 1/2 " travel. Of course, at touchdown the legs are fully extended and 3/4" is available to absorb landing loads. Full weight on one leg just takes it to full compression.

To accomodate a model weight range from 12lbs to 16 lbs whilst maintaining the same static compression I supplied some .030" plastic spacer washers. One washer under the spring in each leg accomodates an extra 1lb model weight.

Thanks again for your appreciation, Regards, Ken.

[Tony Bennett]

they are nice.

the big question is how much.

[kenking-King Design]

Hello there Tony, thank you. The price IS a big question, I appreciate. Naturally, as I think you will agree, one expects to pay more for a bespoke item which is well engineered and of higher quality than the nearest mass-produced proprietary item. That said, it must of course still be good value for money, and the reaction of my client whe he received his oleos confirmed that he considered them to be so. He changed the mounting method after these pics were taken, so his oleos had square plates added near the top of each outer tube, with screw holes for attaching to the wing structure, and that put the cost up a bit further.

If you look for my small ad in the back of RCM&E, ('I can help with milling, turning etc...." you can call me for a chat, or email some basic info of what you might be looking for, and I can then give you an indication of cost. Of course, if you too should happen to be building a 1/4 scale Fairey Junior it will much simpler ! I can also email more pics of the finished job, as handed to the client, andsome notes on the construction method and materials used,

Cheers, Ken King.

[Tony Bennett]

you have pm sir.

i have a list of aircraft that will be needing legs very soon.

ta

[kenking-King Design]

Tony, your cryptic message is intriguing; please explain "you have pm sir". Apart from that, I'm delighted to hear you need lots of legs. Awaiting your 'phone call or email,

Regards, Ken.

[kenking-King Design]

For anyone interested I've added 4 more pics showing further detail, and finished oleos kit ready for delivery to client.

[kenking-King Design]

By popular request

Here are notes on the design and construction of the oleos. The outer tubes are seamed steel tube, 20mm O.D. from B&Q. The legs themselves are 9/16" dia alum. alloy from my stock. A slot, 0.1" deep, 0.125" width and 3/4" long is machined in the upper part of each leg. An M4 threaded steel boss is silver soldered through the outer tube to take a peg screw, basically an M4 capscrew with the thread turned off for the bottom 0.1". The pegscrew engages in the machined slot in the leg to provide retention, to limit stroke, and to prevent leg rotation.

Near the bottom of each leg is a 5mm transverse hole for the stub axle. Axles are retained by an M4 capscrew on the leg axis. Spanner flats are machined on the leg to hold it whilst the axle retaining screws are tightened. I further recommend that the pegscrews are removed during this operation to ensure that any inadvertent twisting of the leg cannot cause damage to pegscrew or slot.

Springs were selected from the range of a well-known manufacturer after much head-scratching, primarily because the weight of the model was uncertain. It was sure to fall between 12 lbs and 16 lbs though, so springs were chosen on the following basis. Of the total available stroke of 3/4", 1/4" would be taken up by model weight on the ground, leaving a further 1/2" compression available. The idea is to have the model 'floating' on the springs to give a more realistic rocking and rolling motion over rough ground than would be the case if the legs were hard sprung against an end stop. This requires the springs to be precompressed at assembly by a specific amount, so that a futher 1/4" compression just balances the model weight. To cater for weight variation a set of 0.030" plastic washers was provided; the addition of one washer under each spring increases the assembly preload by 1/2 lb per leg, or 1 lb total. In this way the additon of washers accomodates model weight in 1 lb increments from 12 to 16 lbs. The O.D. of the springs was limited by the need to pass them through the leg bushes; in other words they had to be comfortably below leg diameter. It should be noted that as the model lifts off the legs extend that further 1/4" and still have the assembly preload. At touchdown there is therefore 3/4" of sprung travel to absorb landing shocks.

The outer tubes have 1/2" long brass bushes at the lower ends and also at about 1" up. The pegscrew and its threaded steel bush pass through the upper brass bush and serve to retain it (though it is also a press fit). The lower bush is press fitted but is further retained by silver soldering through a small hole in the tube wall. Because the tube is seamed there is a small seam bump along its length, and so the bushes required a small flat to to be filed to clear the seam. At the top end of each tube a shallow brass cap is silver soldered in place; the inside face of the cap incorporates a cone which centres the spring upon assembly. The lower end of the spring locates on a short spigot turned on the top of the leg (this is also where the plastic washers fit). The spring, which has ground ends, is thus positively centred within its space. At final assembly everything was well coated with Dow-Corning MS4 silicone compound, to act as a grease and also a water repellant.

This client decided upon a stronger method of mounting than that shown on the model plan, and so square steel mounting plates were added to the outer tubes, as can be seen in the photos.