kenking-King Design

cont'd. Back again after a week of tummy trouble, which at least served to take my mind off two separate ear infections (one each side). Combined, these events hampered progress more than somewhat. Apologies if you find that too much information. I meant to say in my last posting that as the project is now being interest-only driven it will inevitably sometimes take a back seat, and that I will from now on only issue a new post when there has been significant progress, with a reasonable amount of stuff to show you. This post maybe doesn't completely satisfy that brief, but hereafter I'll stick to it, so there may be barren periods to get through, particularly with Christmas approaching. After some consideration a design change was made to the belly bands. I decided to make them of brass and to solder them in place, rather than using the aluminium ones and trying to bond them in a precise position whilst sliding them along the cylinder. In the light of later experience that turned out to be a good decision. Belly bands locate the damper cylinders correctly within the legs, so position is important .... After that the filling and vent ports in the lower damper endcaps were drilled, and tapped 10 BA, holes angled as my earlier sketch suggested. I ground down the OD of a small centre drill and used it to provide a conical seat ...... with 10BA steel cheesehead screws as plugs, bedding down onto them. They are VERY SMALL ! Because they sit within the lower leg tube I had to make the heads slightly conical so that they did not extend out past the endcap diameter to foul the tube bore. For assembly of the damper cylinders I bought the recommended Loctite 603 and 7603 Cleaner and thought I would bond in the UPPER endcaps first, following the suggested procedure after cleaning, firstly wetting a 3mm band inside the brass cylinder, then the mating land of the endcap, bringing them together with a twisting motion. HAH, I wish ! No sooner had the two parts caught sight of each other than they were STUCK, really STUCK. No chance of full engagement nor alignment. To illustate that I'm a slow learner I can tell you I tried three assemblies before deciding something had to change ( once I'd used carefully applied heat to dissassemble three failures, that is). After carefully rereading instructions from Loctite, plus the Product Data Sheet, I realised I was woefully short of the recomended diametral clearance of 0.1mm, having proudly made things a nice sliding fit. Glossing over the sordid details, including turning a few thou off each encap, I tried again with SUCCESS !! Boy, that is some adhesive. 'O'rings were fitted to all eight endcaps, and the next steps considered. Final assembly required pistons to be affixed to spindles, and the spindles to be inserted into the cylinders and through upper caps. A LOWER encap would then be slid a little way onto the spindle before very careful application of 603 as before, followed by a short prayer and rapid insertion into the cylinder tube. OK, procedure established, but before following it I had to modify the pistons slightly by relieving part of the OD to reduce occasional binding noticed during dry runs. That done it was time to bite the bullet, and thankfully all went well. Endcaps went fully home and I avoided glueing any pistons to bores .... PHEW !! Having allowed some hours for full adhesive cure, as suggested, it was time to fill with oil. My wife shares the typical femal abhorrence of any fluid such as engine oil being introduced into the domestic environment so I was denied the comfort of the living room, but proceeded to plan. First lesson -- don't bother trying to fill the syringe by sucking up through the needle, unless you have all day. Second lesson -- having successfully filled said syringe, it's awfully hard work to pump it into the cylinder. Shortening the needle will help enormously ! Here you see needle, cylinder, and two of those VERY SMALL screwpugs I mentioned .... and here is a completed cylinder awaiting assembly to its spring and springcap prior to insertion into a leg .... Piston action is smooth, little resistance to movement in one direction but quite noticeable in the other showing that the piston valve really works. Relieving part of the piston OD has definitely reduced the damping effect, by shortening the restricted path length for the oil passing the piston rim. Substituting a more viscous oil may be something to consider after more trials, so still some work to be done, but I'm encouraged by what has been achieved, and VERY pleased to have those tiny fiddly bits behind me. More at some future date, and a Merry Christmas to you all, Ken

cont'd. A lot of air has flowed over the wings since we last met, and I'll explain why. Over the past several months it became difficult, nay, impossible to contact my client Ben via the usual email and it beame clear that he has other matters occupying his entire attention. I don't know whether or not he has started the build, which he was about to do back in August. I sincerely hope he is well, and that he will eventually be able to pick up where he has left off. A couple of weeks ago via snail mail I explained to him that with my name attached to this U/C project I don't want it to just fizzle out (though it must have seemed to you all to be doing just that), and so proposed that unless he notified me of an objection I would continue the work and the blog for my own satisfaction and the interest of you chaps. I haven't heard anything to the contrary, so it's onward and upward. To recap, I fear I kind of lost my way rather with the long retraction arms, and my idea of plug welding confirmed what you probably thought, that it was an unnecessary complication and there were better ways. You were right, and so they are awaiting a new approach whilst I have got back to work on the spring/damper units. The piston valves have changed slightly to save a little length, as every millimetre counts. The valve bodies now have three equispaced drilled valve ports ............. whilst revised valve discs are simply M4 washers, opened up using a taper reamer to fit freely on the valve body, and flatted and lightly polished using wet & dry on a piece of plate glass. They are retained by a homemade circlip, just an end coil cut from a handy-sized spring, with some axial clearance for oil flow. The photo below shows one assembled valve, and in the other valve bodies you may be able to detect the shallow annular grooves which link the three holes and increase the area of transmitted pressure against the disc .... I tested one of these in the little dashpot rig from way back, clipping it to a length of spindle rod and pushing it down through the oil to judge resistance. I then turned the piston over and repeated the test, and I'm delighted to report that the valve arrangement works very well, and there is a significant difference in resistance felt in one direction compared to the other. Given that the diameter of the three holes was pure guesswork I was pleased to find the difference felt about right. I can't be more scientific about it than that; I don't have the means to accurately measure the characteristics, but for the moment I'm happy. A lot of measuring and arithmetic then went into determining groove positions on the spindles for E-clips to hold the piston, and checking clearances and lengths of this, that and the other, but finally spindles were grooved and cut to a final lentgh of 115mm. Damper cylinders were cut from 3/8" i.d. thin brass tube, and a dry assembly put together. At that point I concluded that piston/cylinder bore clearance needed to be increased to make allowance for some manufacturing tolerance, if all binding was to be avoided, and that in turn dictated moving to a more viscous oil than the silicon variety I had bought. Engine oil as used in the Mondeo has been substituted and I think all will be well. The next photo shows a dry-assembled spring/damper cartridge and the relative position to to where it will sit within a leg unit. The bellyband around the cylinder locates against the internal step in diameter where lower and upper leg overlap. You can't see it in this view, but the spindle DOES protrude through the lower endcap by a couple of millimetres. The final photo is the same but with the addition of a 'kit of parts' to illustrate how things go together .... The Loctite folk have kindly recommended 603 for assembling endcaps to cylinder (bellyband too), having good oil resistance, and I'm awaiting delivery of that, plus SF7063 cleaner. The eagle-eyed among you will have noted complete absence of filling ports in the lower cap, but that's only because I haven't drilled and tapped them yet. Be patient ! I expect to do this while the Loctite wings its way toward me, and a week from now hope to have assemblies bonded and filled. All fingers and much else will be crossed in the hope that any oil leaks will be negligible. You'll be the second to know, Regards, Ken

Hello Alan, yes it was a slitting saw job, and I forgot which way the backlash on the leadscrew went, hence nick. Others may be wondering why the first clevis soldering went awry, given the near-perfect result illustrated. It was my own fault, so doubly annoying - I thought I'd just fill that wee step with solder, and one thing led to another, as it does. The final results, after some injudicious filing, were less pretty than desired, so moved to the back seats. Method of activation is up in the air (boom boom) but it could be screwjack, or perhaps worm and wheel quadrant. It's not yet decided whether individual activation in each nacelle, or one central drive with sideshafts will be used. A dummy nacelle is really needed to help make these design decisions, hence the drive to complete the linkages and have something to play with. Unfortunately shed time has been limited lately so it's all taking longer than one would wish, and it's made for a very long drawn out section of blog I'm afraid, just a collection of snippets rather than an epic episode, but please continue to watch this space, it can only get better ...... can't it ? Ken

cont'd. Still working on the arms, making the clevis ends, in two different ways as a learning exercise. The first method involved milled clevis pieces, slotted at the other extremity to fit over a retraction arm. Eagle-eyed reviewers will note a wee step in the slot wall of this one due to a momentary lapse in concentration. Having clamped the two parts together in an old toolmakers' clamp reserved for this sort of duty, I played a gas torch over the faces and aluminium soldered them into one .... then flipped over and did the other side. That looks neat enogh doesn't it ? In truth they didn't all come out quite so well and though perfectly serviceable I've downgraded them to be the rear ends of the arms, tucked up at the back of the wheelwell. I may end up changing them once the method of transmitting torque to the back ends of the arms is established. Tackling the promoted front ends somewhat differently, I made clevis side-pieces from 2mm sheet, with a 0.5mm rebate milled along one edge. The sheet was then drilled, and cut into strips 8mm wide, each strip having three holes. The purpose of the rebate is to contain the flange of a brass bush, a rough prototype of which can be seen. Pegging two pieces to an arm (the original end-hole of which has been cut off) shows how the clevis will be assembled before being clamped, using that good old tool again. With pegs removed I hope to sort of plug-weld through the holes with solder, effectively forming rivets. (Yes, I know I could just have used rivets, thanks) As the bush flange equals the rebate depth, the clevis internal width between flanges is the same as the arm thickness, which by a stroke of great good fortune is the same as the link end going in there,with a few thou clearance. Amazing or what ? The next post will reveal the results of plug-welding, so fingers crossed. BTW, I've been thinking about the damper cylinders and method of assembling endcaps to tube body. Out of consideration for the Oring seals I've decided that heat should play no part, so will consult with Loctite Technical Service to ensure using a product guaranteed to be proof against silicon oil. That shouldn't be difficult, I think, and will be a much more sensible approach. More later, Ken

cont'd. Well Dennis, assembly is certainly nearer, but we're not quite there yet. I'm very pleased to tell you, however, that persuading the Oring seals into their wee pockets was no trouble at all. Two cocktail sticks, one with a square cut end, did the job in short order, 'almost as if it was meant', as a friend of mine usually acknowledges the conclusion of any meticulously planned and executed venture. Before I can proceed further I need to provide means for introducing oil into the assembled cylinders, and for venting air at the same time. 'A glaringly obvious requirement' I hear you cry, and justifiably so, nevertheless it has the undeniable air of afterthought about it. In truth, I had expected there to be plenty of room to whack in a couple of holes, with provision for threaded plugs, and hadn't overly concerned myself with it, but now find it's a bit tight, though achievable I think. The accompanying diagram says it all, being a section through an endcap and seal assembly, with my exploratory thoughts on angled hole positions sketched in. When I tell you I'm hoping to use 10BA plugs you'll have a feel for the situation. With a degree of optimism I've acquired some nice plastic syringes with blunt needles, with which to inject oil through said plugholes. Another prerequisite for assembly is to have the pistons finished and attached to their spindles because they in turn have to be threaded through the endcaps and tube before the final soldering together, at which point I'll have to have effective heat sinks in place around the seals so I don't frazzle the Orings. You see what I mean Dennis? Definitely not there yet, and if you're wondering whether a little more forethought might have avoided some of the obstacles catalogued here, well, you are not alone, but HeyHo, sometimes one has to be the fool rushing in whilst the cautious and wary angels never get started. It's a viewpoint, OK? Later this evening, by way of light relief, I dowel-pinned my prototype retraction arm sidemember to three more blanks, and entertained myself on the mill, cutting off excess and matching the profile .... As you can see, they taper to each end. Pairs will be connected by a stout plate at the front, where those dowel holes will be cut off and a clevis fork substituted, ready to mate with the tubular links made earlier. I spent some time cleaning up edges as I was marooned in the shed by three hedgehogs getting frisky on the nearby patio, and not wanting to interrupt production of hoglets, I kept busy until they'd called it a night. Lovely! More later, Ken

cont'd. The endcaps have lost some weight as promised, and the components required to complete the Oring housings therein have also been produced - just simple washers .030" thick. They are soldered into the larger recess, creating pockets behind them for the Orings to live in. The photo shows on the left an endcap for processing, and below it a washer and solder ring, the latter formed by winding turns of fine solder around a mandrel and slicing through. On the right is a soldered item. A weighted probe held the washer firmly down in its recess during heating and subsequent cooling to maintain spacing, as otherwise such small items tend to bounce around and settle in arbitrary positions of their own choosing ...... Here are the eight finished endcaps, although the ugly one (that's why it is at the back of the group) may need to be reworked .... My next trick will hopefully be the insertion of one of those Orings into each housing, with the aid of some lubrication and dexterous manipulation of cocktail sticks. Holes in the washers are larger than spindle diameter, covering only the outer 75% of the Oring, thereby giving me a little more room for manoeuvre. In the next posting I'll let you know how I got on, Ken