A man needs a seat

 Acroduster  Comments Off on A man needs a seat
Nov 262019
 

In order to fly by the seat of his pants, a pilot needs a seat. For weight saving reasons this one used aluminum straps. I am sure that solution was fine in sunny California, but I doubt it would be comfortable over here. Never mind, scale is scale! I might at some stage add the fake rivets that secure the ends around the tubing.

I just realize I forgot to add the attachment points for the safety belt.. Soldering stainless steel (750 C) and alu (melts at 350C) don’t go together. Guess I’ll have to fake soldering them (JB weld to the rescue)

The back support of the seat is made from heavy canvas, I must have a look if I can find some old suitable trousers!

I suppose it would also be a Good Idea to make sure you can reach the servo from the bottom of the fuselage. I can feel a non-scale access hatch coming up!

Not visible anymore is the connecting rod between stick and servo. I replaced the first solid version by one that can telescope. Just to make sure we don’t get any unwanted inputs from ye driver! It works like a servo-saver with 2 springs on either side of a solid point. I have approx 15 mm travel each way. I might do a drawing for that, lest I forget how clever I was.

 Posted by at 7:33 pm  Tagged with:

Something old..

 Acroduster  Comments Off on Something old..
Nov 262019
 

Long ago I had a Yak that I had to retire because of a wing-tube that approx 3 degrees dehidral (too many snaps I guess). Anyway, I usually keep all the good parts of a retired air-frame. So I had the actual bracket for the wheel. I had a single nice looking wheel, and a bit of carbon. An old wheel axle provided the new bearing for the part.

The result looks good enough for now. The wheel axle needs changing to something steel (brass won’t last long) but that is a later job. The hideous bolt on top will also need hiding at some stage.

And yes, I want to add the weight now, so that later-on I will not have any CG surprises!

Funny enough, Probuild still caries these tail-wheels! (I got mine sometime 2002 I think, when I used to live in Trowbridge/ UK.)

Rear end skinning

 Acroduster  Comments Off on Rear end skinning
Nov 252019
 

The panels for the access to the rear end are made from 0.3 mm stainless steel. The main challenge was working out a method to fit the panels with screws as per full size. After the inevitable ”not fit for use” parts, I think I worked out a method that I can use at the front as well, without adding too much weight. I am using 2 mm steel strip, partly drilled and cut at the locations I want to keep. I use the panel for alignment, and when the first 2 point are soldered, I remove the panel and solder the remainder. Afterwards I cut of the bits no longer needed. Once the lugs are prepared, they are tapped with 2 mm. At present I am still working on the cutout for elevator, but already it looks great.

In hindsight I should not have followed the plans for locating the tabs. It would have been better to place one or 2 at different locations, i.e. I now need to add 2 extra to hold the front part of the cover and an additional one to hold a filler plate above the hole for the stab. Hey, it’s a Homebuilt!

Prepare the little lugs, next time I need to make a wider cut to prevent the silver flowing up the gap. Also need more clearance at the bottom part. This was the last one, where I thought I could get away with just a bit of relief.
First tacked the other side at 2 locations, using the panel for guidance. Next solder this side.
Left part still needs shortening, right is short enough, just needs a bit of tlc.
and the finished part.
Looking at the shiny side. Next is removing enough material for clearing the stab/elevator.
and the last bit for today..

Checking alignments

 Acroduster  Comments Off on Checking alignments
Nov 192019
 

It is always a good thing when the magic red lines end up where they should..

all the zero’s!

Making the bottom bracing means you have to get everything lined up properly. You don’t want to start pulling this out of whack. Since I went through all the trouble making the clevises, I might as well use them. Officially the stab side is made by drilling a hole in the flattened streamline tubing. Guess no one will know except me (and you). It is also easier at the moment to make them that way, so that I can slip the streamlined ABS tubing over the 3mm rod.

Printing a quad of 3mm streamline fairings. ABS and 215 mm high. Layer height is 0.2 mm. dimensions are 3.9mm x 10mm deep (OD), just enough for a 3mm rod to pass through..
busy at work as we speaks. I added a base for stability, the previous set started to wobble ever so slightly at the top of the print.

In order to give the plastic some time to cool down and to provide some stability, I print a ‘cloverleaf’. The ends are barely touching, it comes apart very easy. First trial looks good. The texture looks quite rough here, but a small amount of sanding smooths things out in no time at all. I still want to add a layer of glass, and tidy the ends to make it all look very much like ”scale”.

another variation, I made this after looking at WW1 aircraft.
These are on a full size one.

Also made a slightly different version, this one has a tapered front section. It looks nice too. I only flattened one side, where the screw goes, that leaves a bit more flesh for the thread on the other side. In the picture above I drilled it for a 3 mm bolt, reduced the bolt-head to 3.9mm, so it sinks into the top bit. Anyway, 3mm is too big for a 6mm rod, but the idea is good. (Since I now have the lathe setup better, the results are better too. Not good, not machinist good, but hobby good enough for the job. I drilled the 3mm screw with a 1.5 mm hole, in order to put a locking pin through. Yes, too much work. I agree (for now)

making more shiny bits

 Acroduster  Comments Off on making more shiny bits
Nov 182019
 

Just so I remember the sequence of work next time around.

Make sure you have the proper radius tool to make the nose radius. I had to make my own, which was not as hard as it sounds. Just take you time with the dremel. This was an old tool that I (ab)used for this purpose.

Drill a square piece of alu/brass or whatever with a 6 mm hole so that you can securely put the brass rod in the tool holder. Since I don’t have a 4 way chuck, mine was drilled off-center but that does not matter. Tap a few holes for M4 bolts to hold the brass rod. The are other methods to do this, I simply show what I did, not because it is the best method.

Cut a piece of 6 mm brass approx 20 cm, that way you can make ca 10-12 pieces at the time.

Drill the 6mm rod with a 2.5 mm drill, at least 20 mm deep. This will be tapped to M3 later. (If you have a 2.4mm drill, you should use it, 2.5 is slightly oversize if I remember correct)

Round the nose with the specially radius-ed tool. You need to do this before cutting the slots. Believe me, this will work better.

Next transfer the rod to the aluminum holder. I want to cut ca 10 mm on both sides, so make sure it sticks out ca 12 mm.

Now comes the trick: make sure the outside of the blade lines up exactly with the outside of the brass piece. You only want to cut a saw’s width off the sides. Run lathe at a fairly high speed, and feed slowly. You really want the blade to cut. Repeat on the other side. Next eyeball the blade in the middle and make a 6-7 mm deep cut.

This was the first try, later I rounded the nose before cutting the sides.

Insert the rod in the chuck again, and reduce the backend to ca 4.5mm.

Use a bit of fine sandpaper to rub off and smooth any bits that don’t look good. When done and happy, part at a total length of 17mm.

I could make 50 more, then select the best. Practice makes perfect and all that. For the time being, TLAR!

I tapped the holes with M2, and will install proper steel bolts when all is done.

These few bits took you all day? Yeah, but I did disassemble and clean up the lathe as well, There was some play in the cross support that was hard to get rid off. It’s all good now 😉 (look at mini-lathe.com for guidance)

 Posted by at 5:37 pm  Tagged with:

I did not like the clevises …

 Acroduster  Comments Off on I did not like the clevises …
Nov 162019
 

..so fiddling around I managed to make a better one, that looks more scale like. I did have some thin saws from the pound shop so here we goes. Those things are undoubtedly not made for what I use them for, but as always, go slow and be careful. I tapped a hole in a 12mm rod I had lying about, and fitted the blade. Clamp a 6 mm brass rod in the support and go slowly. The design is basically copied from Dubro 4-40 rod ends. I have a few of those, but they are tapped for 4-40 thread, with is approx 2.8 mm. Not enough flesh on them to tap a M3 hole, and I don’t have any imperial taps/dies lying around to make the rods. Hence the ‘need’ for DIY.

They are ok, but look too big
result after a good days work..
in real life it always looks better then on a photo.
This looks really good, and the size look right!
Machine-made and Me-made

Next step is make a handful more, and get the streamline tubing for the bottom braces. Stab side of the tube will be flattened with a hole drilled through (easy), the other side is adjustable like above. In fact, this adjustable one goes on the fuselage side, but that does not matter.

So, 4 in total for the bottom, m3 threaded. 8 for the top, solid with a hole for the bracing wire.

Wow, many hours of fun coming up!

The smaller the parts, the longer it takes to make them.

 Acroduster  Comments Off on The smaller the parts, the longer it takes to make them.
Nov 122019
 

There must be a law for that! Anyway, at the moment of writing I have half the brackets done. Most challenging part is cutting without cutting meat-ware. So far all fingers are present. Material is 0.8 mm stainless, not the easiest to work with. I had some nice clevises from Pete Tindal*, they look good and do the job just fine. They were meant to be used with glue and a 3 mm carbon rod, but cutting a 4mm thread in the hole works great. Cutting a 4 mm bolt to size and drilling a hole for the wire seems to work. I might tidy up the bolt end, it does not look to grand. ( *only people of a certain age will know Pete)

Pete Tindal clevises. He who keeps everything has a lot of junk.
Top elevator, cables, bottom streamline tubing.
Polishing everything will make it look better!
cut narrow 6.5 mm strips
some elbow grease required to make them look nice
and bend them the required 129 degrees. (141 degrees for stab side)

Elevator servo stuff

 Acroduster  Comments Off on Elevator servo stuff
Nov 052019
 

Servo needs to be hidden under the seat, so I built some bits to do just that. All overkill of course. I also remade the pivot of the control stick. The washers I has used had an internal diameter of 3.2mm. The bolt was 3mm. Very sloppy! Same with the link at the bottom. It took some time, but now it is all slop free!

Update: did not like the crossbar, it interfered with full up. So changed things a wee bit, still same servo position.

Elevator control chain.

 Acroduster  Comments Off on Elevator control chain.
Nov 032019
 

Need to get from the (future) servo under the seat to the back-end in an orderly fashion. I’m using the full size method as guide. Main part is the reversing bar behind the seat. It has to be zero play. No play, whatsoever. After the usual fiddling around for a while, I got it sorted. It’s a once you install it, you can never change it construction. Failure here is no option. The bolt at the bottom prevents the assembly sliding out of the bushings. It does not support anything. The 2 little square supports were reamed out to provide a zero play bushing.

Next will have to be the construction of the stick assy, and the mechanical interface to the servo. Lot’s of fun ahead!

pushrod is for illustration only.
and something for the pilot to hang on to.

I am only installing the main stick, front seat is ”occupied”. Not sure yet if I am going to use a separate servo(s) to drive it. Separate seems safer, since there is a reasonable mass in this contraption. Might build a pilot with power arms 😉

full down..
full up, looks like it’s enough..

The stick has to be fixed with AN4-22 bolt, 4 washers, AN310-4 nut and a AN380 1-2 cotter pin. Yup, M3 bolt and nut will do fine! (for the curious: AN4 is 1/4 ” = 6 mm. So 2 mm would be scale. Since those 2 mm bolts are usally quite soft, I won’t waste my time installing one, they will rattle loose in no time at all. The nut is a castle nut so you can put a cotter pin through the bolts hole to stop it going awol. I know you wanted to know all this.

..more tail-bits..

 Acroduster  Comments Off on ..more tail-bits..
Oct 282019
 

..many times you have to make parts before the other parts that need to go on before the parts that you need to fit to get the job done. This was one of them. Needed to make more hinges. Not difficult, just fiddly, and a bit dodgy, since I try to cut them on the lathe, with a dodgy china cutting wheel going full speed. However, hats of to the china-folk, I have not had a single one fail on me. So far I have used approx 20 odd discs on this project.

cutting some hinge-parts.

After checking the tail, I noticed the main spar was bend. This appears to be almost inevitable when you heat bits. I decided to simply cut the middle, and add a sleeve. Problem sorted. My metal working skills don’t go so far that I can predict how much distortion I will get. Of course I could make very expensive, very heavy jigs. yup, I could..

fudge, I had to cut the front, because the rear was not straight after brazing..

A bit of a showoff.. Starting to look like it wants to fly!

1569 gram, still smiling

Just one more weighing session. 1569 grams as seen here. Good stuff!

enough done for today!

And I am calling it a day. All in all it does not seem much, but I am happy with it! The section above weighs 300 gram. As a comparison: the ”light” elevator from my 2.5 meter Extra weighs also 600 grams. Ok, there’s 2 servo’s included in that figure, but still..

Finished the rest of the elevators today, another milestone reached! Also bolted the motor back on to get a feel for the CG. At the moment I am still slightly nose-heavy, so things are good! I don’t expect to have to add any of the grey gravity stuff.

yes, that’s 288 grams!
That’s the elevator horn-thingy sticking out there. Added a bit of wrap around as well.

The rear stabilizer mount consists of a single bolt, as per original, the front is made up of a few gussets. I probably simplify that part. Not sure how, but simpler as original. (too many small bits that fall apart when you heat things up, is the main reason)