Vitolds wrote:length - 515 mm
width -?
Pipe 25x25x2 mm
That crossbar is only temporary - it is there just to hold the spacing between the outer bars. It has 3mm gussets riveted and epoxied underneath but is just held to the outer bars by by M4 bolts tapped into the outer bars. Once the seat pan is made, it will be held by M5 tapped into the Al blocks epoxied into the ends of the outer tubes. Depending on how I decide to mount the foot plate, the cross bar may be retained (to attach the foot plate bars with a stainless piano hinge?) or removed and the foot plate attached with M4 x 40 through the same Al block and tapped into Al blocks in the foot plate arms. If the cross bar is kept, it will be attached with M6 x 30 FH and nutsHow are the top outer bars joined to the cross piece, and is that cross-piece 239 - 2 x 25 = 189 long?
The stub bars on the upper frame started as 292 mm long, but were trimmed (beveled) with dremel cutoff wheel after I discovered interference with the lift bars when down. Final length may be a bit shorter. Stub tubes on the lower frame were 222, but also beveled (less so than the upper stubs).How long are the inner stub bars?
You are quite correct; the upper side bars are shorter than the lower ones. Actual length is 482 mm (and you'll notice other 2 mm differences above). My drawings of the tubes used 2mm thick lines centered on what shows in the wireframe, so a wireframe of 23 mm x 480 mm is a finished tube size of 25 mm x 482 mm. (I didn't get so fancy as to split the rectangles and have 2mm lines at the side and hairlines at the ends.You say the overall length of the frames are 515mm, but the drawing shows the top outer bar is 480 long.
The sliders are cut from nominal 20 mm thick POM (acetal or Delrin if you prefer the brand-name stuff) sheet stock (which, as delivered is always >21 mm). They are 50 mm x 23 mm x 21+ mm and then hand milled (dremel burr and very course double cut file) for a free slip fit in the tubes. They are blind drilled or through drilled (as appropriate) a full 0.5 mm undersize and reamed for a tight fit of the 8mm dowels. Reaming POM needs slow speed and high feed or dimensions will be way off because of heating.What is the POM slider?
LROBBINS wrote:Is carbon fiber filled nylon more or less rigid than 6082? I had though of changing the lift tubes (which are the only highly stressed ones) to carbon fiber/epoxy but what's readily available has only a 1mm wall (at most), having them custom made would be too costly, and I don't know whether they are smooth and uniform enough inside for the sliders.
The top frame has only two longitudinal bars. What the drawing shows are those two plus the two inner and two outer lift bars, and they are all 442 long. The inner lift bars have reinforcing tubes bonded and screwed on top at the rear. One of them is drawn off to the side. They are 238 mm long and tapered as shown. I hacked them out of some scrap, and one of them actually was an earlier mistake with a slider slot already cut in it, and then I further massacred them until I figured out how to mount the over-tilt limit switches in a way that they don't hit anything anywhere during the movement.Oh, BTW, what is the length of the top inner tubes?
I'm guessing that you are referring to the lower frame. The longitudinals are slotted on the inside only at the front, and the stub tubes mounted at the rear are slotted on the inside. There's no slot at the rear in the long tubes to be covered.Also, if I read your drawing correctly, the slot on the inside of the outer tube is partially covered by the stub epoxied to it?
LROBBINS wrote:So far one error, and it was mine. The CAN controller/transceiver boards have a through-hole 16MHz crystal and my layout had it top layer even though all the ones I built by hand have it on the bottom - which is where it should be. The supplier did what the files said so I have to remove and re-solder 25 crystals.
Irving wrote:Welcome to the fundamental differences between 2D drawings and 3D solid modelling!
LROBBINS wrote:Is carbon fiber filled nylon more or less rigid than 6082? I had though of changing the lift tubes (which are the only highly stressed ones) to carbon fiber/epoxy but what's readily available has only a 1mm wall (at most), having them custom made would be too costly, and I don't know whether they are smooth and uniform enough inside for the sliders.
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