Tiny Trainer - phase II - landing gear and motor

[wlouisharris2000]

Thinking about a landing gear for the tiny trainer I am building. Just wondering if anyone has any photos of stuff they have tried. I may end up using bbq skewers on the lower part of the fuselage; then just using the same method as the FT Flyer. I just think I may run into issues breaking props with belly lands.

I weighed my Trainer w/o any electronics - it's about 5.1 oz.

I went with a motor that someone suggested:

http://www.headsuphobby.com/Power-Up-250-Sport-2300kv-Outrunner-Brushless-Motor-F-115.htm


Just a plug for HeadsUphobbycom. As someone on RC groups told me - "They ship fast."

The low end thrust is 7oz and I use a 2 cell 500 mah battery so I may be ok.

I'm curious to see what other motors people have used. The motor option 2 Flite Test has looks great and the price is right but 7-20 days for shipping?? No thanks.

http://www.banggood.com/ZMR-1804-24...ation-Outrunner-Brushless-Motor-p-923424.html

I finished building the 4 channel wing. Where I screwed up is I did not make the score cut on the ailerons before I glued the wing down. This caused some crumpling near the fold which could have been avoided. Anyhow, it still looks functional. Overall I made some mistakes on this plane, but I still feel like it will fly decently.

 

[Spastickitten]

Thanks for the link to heads up hobby. They have the same size motor as the bangood link does
http://www.headsuphobby.com/Emax-MT1804-2480kv-Motor-Plus-Thread-A-080.htm

 

[wlouisharris2000]

Thanks for the link to heads up hobby. They have the same size motor as the bangood link does
http://www.headsuphobby.com/Emax-MT1804-2480kv-Motor-Plus-Thread-A-080.htm

You're welcome. Those guys at Heads Up are shipping machines. I usually will order stuff on Saturday and it's at my doorstep by Wed.. Then they only charge 2 bucks for standard shipping. I already ordered the Power Up so hopefully it's not too much thrust for the TT.

 

[Spastickitten]

no such thing as too much... I bought my first airplane part from them, and my second

 

[LandBasedMammal]

There is a lot of good info on the Tiny trainer Build article. I made some landing gear for my Tiny Trainer as did a Forum member named Torf.

http://forum.flitetest.com/showthread.php?17139-FT-Tiny-Trainer-BUILD

 

[wlouisharris2000]

There is a lot of good info on the Tiny trainer Build article. I made some landing gear for my Tiny Trainer as did a Forum member named Torf.

http://forum.flitetest.com/showthread.php?17139-FT-Tiny-Trainer-BUILD

Thanks. I found what you are referring to.

http://forum.flitetest.com/showthread.php?17139-FT-Tiny-Trainer-BUILD/page11&highlight=landing+gear

This is kind of confusing; I've looked at it for about 30 minutes. I trimmed out 3 pieces of utility flags based on the specs. I'm confused about the hooks he uses on the top of the plane. I wish FT would include plans for a landing gear because I'm sure I will destroy props without one.

 

[wlouisharris2000]

I'm also looking at the Simple Storch video and seeing if that is a possibility. The 3 pack swappable method seems like it could work as well; possibly with smaller dimensions.

 

[LandBasedMammal]

You might hit up Torf for some info. Mine are really simple and work well. They are exactly like the swappable but with a removable velcro plate instead of bbq skewers. Only takes a few wire bends to make. Or just skewer it like a swappable. A gift card backplate will help wear and tear.

 

[wlouisharris2000]

You might hit up Torf for some info. Mine are really simple and work well. They are exactly like the swappable but with a removable velcro plate instead of bbq skewers. Only takes a few wire bends to make. Or just skewer it like a swappable. A gift card backplate will help wear and tear.

Yah, I will hit up Torf. I see your method and that looks pretty easy. What kind of wood did you use for the plate? I'm thinking i might use a painter's stirrer. I'd rather avoid using more skewers.

 

[LandBasedMammal]

It is 1/8 inch plywood; Flooring underlayment scraps. There are pictures on the tiny trainer build thread but generally make the plate as wide as your fuselage and longer than the skewer reliefs. Reliefs are around 2 inches apart to match the skewers from the swappable build. Mine are 2'w x 4"l. I cut a few to make for different planes.

 

[Torf]

The advantage to LandBasedMammal's choice is that it is simple and lightweight. My brother also uses that design in his new Trainer. The drawbacks are that it is springy and rather flexible. This can allow the "heavy" landings to crunch, splay, bend, and warp the gear, and causes the wheels to go a bit crazy on touchdown.

The advantage to mine is pretty much the opposite. It's rigid enough to handle any landing that wouldn't otherwise be called a crash with very little bouncing or flex. It's also flexible enough not to need constant maintenance. On the other hand, it's drawbacks include it's more substantial weight and it's more complicated construction.

I'll see if I can shed some insight on my version of the landing gear. Sorry the instructions were brief. Maybe I can add a little info along with a few additional pics and see if it's more clear. Also, none of my measurements are super precise, and the angles are eyeballed and approximate. It doesn't have to be perfect, it just should closely match the opposite side, and allow the plane to track reasonably well.

Once complete, the rear section is approximately 8" long and the front section is about 5.25" The "hooks" utilize about 1" of wire at each end. Keep in mind that the pictures show a completed gear, so you'll have to ignore pictured elements that have not been described yet. It's also hard to assemble this while on the plane. Easier to just use the plane to reference for fitment, and assemble everything off the plane. Once complete, then install. I used Dubro 1.75" wheels for this project. I suspect that anything from 1"-2.5" would work fine depending on your surface.

1. Start with 2 wires about 15.25" long each. Make an approximate 60* bend at about the 9" mark on each wire. This bend is where the axle goes. I then eyeballed the front strut (shorter section) at about a 90 degree angle to the top of the fuselage, adjusting the axle bend until it roughly aligned with the skewers in the fuselage. Bend the second wire as congruent to the first as possible.

2. Bend the hooks, using a pair of pliers or two. The more radical hook on the short strut is designed to support the front skewer, and the other one supports the rear. The shape of the bends is intended to accommodate the skewers as well as a small rubber band on the shoulder in front of each skewer. Try to keep the hooks in the same geometrical plane as the axle bend. Try to bend and twist the parts of the wire so that it basically lays flat, and both halves of the gear are congruent.

3. Mock one side of the strut onto the plane and mark the struts, front and back with a little sharpie mark where the bottom of the fuselage crosses the struts. Basically the bend happens at the same height as the bottom of the fuselage. Bend the struts outward from the fuselage at the marks at about a 30* angle. The axle bend is supposed to splay outward to give the plane stability. This leaves a distance of about 5.5" between the axle bends. The other strut bends in the opposite direction because it is on the other side of the plane. Make them as congruent as possible, keeping in mind that the struts are now a mirror image of each other. Once the struts are bent outward, you will probably have to twist or bend the hooks back into a line. Just make them as straight as you can, making small adjustments. Doesn't have to be perfect, as you can see from my pics.

4. Cut a 7.5" length of wire for an axle, and secured it with two small zipties. The axle passes through the sharp axle bend, and the zipties go around the axle bend. Leave the zipties somewhat loose until you have everything installed on the plane. See picture if this doesn't make sense. Lastly, I installed the wheels with a hot glue hub, attached the landing gear to the plane and tightened up the little zip ties to prevent major axle slippage.

The assembly itself fits onto the plane using 4 small rubber bands. Two, over the fuselage squeezing the shoulders of the skewer hooks and the other two directly under the fuselage squeezing the struts together from the bottom. (These lower bands have to be installed on the gear before fitting to the plane) This makes the struts conform roughly to the sides of the plane. It's a lot easier to install the landing gear before the wing is attached. I use the wing rubber bands to help hold the landing gear hooks on the skewers. With the rubber bands laid over the top of the hooks, they tend to stay in place in all but the roughest landings.

Previous pics for reference:

 

[wlouisharris2000]

Thanks again Torf. I created the wires without any issues. That part is not as complicated as I had originally made it out to be. The only part I'm having issues with now is the zip tie connections. I might need to get smaller zip ties, but I can't get the tie to fasten snugly enough. I can see how it would be helpful to have a big thicker gauge than landscape flags. I'll have to go back and watch the video again, but it seems somewhat similar to the Simple Storch landing gear; only they glue wires on to the bottom. I'm thinking it may be easier to attach one of the wheels before I make the zip tie connection; not sure why that part is giving me fits.

 

[Torf]

Small zipties might be necessary. They are the same ones we use around the house for small jobs. Probably about 3/16th of an inch wide and maybe 4-5" long. They are easy to find at home improvement stores.

When cranking them down, don't force it too tight too fast. Actually, you can slide the axle back and forth, or twist it on my plane with your fingertips. The zipties don't hold it snug enough to prevent all motion. The intent is to allow the gear to splay out a bit on a rough landing. The axle allows enough room to do so and the zipties provide enough friction to resist it just a bit, to retain the axle position during flight, and to help retain rigidity.

The easiest way I found to install the axle was to make a larger than necessary loop from one ziptie. Then place it over the axle bend, sliding it far enough up the struts to be out of the way, then to insert the axle between the bend and the ziptie. This will sandwich the axle in place once the ziptie is tightened down. The opposite side should be easy enough to figure out from there. If you decide you need them tighter, then use a needle nose or something and click them one click tighter. Too tight, and they will change the angle on the struts.

I watched the Storch video some time ago, and I think they did a similar thing. If I recall correctly, the Storch uses two supports under the fuselage, and a single under wing strut as the actual axle. There isn't a straight axle, which makes more sense on rough airfields. Less likely to be damaged.

Using a straight axle gives up a rough field capability, but is also lighter and with lighter gauge wire, tends to keep the wheels parallel more effectively. It's also easy to replace if it becomes too bent for use.

Feel free to experiment and improve on my solution. It was literally version 0.2 on my first ever RC plane built in April, so it isn't as though I was drawing on years of experience or anything.

Good luck with your plane!

 

[wlouisharris2000]

I got all the electronics today. I had to make the firewall so did that and only had enough time to mount the motor. Going to bind the transmitter and test the motor tomorrow and hopefully have time to mount the servos for the 3 channel. Odd thing the prop saver is not big enough so will have to drill it out a bit larger. Other than that it's coming along. Great thing about these planes is you can take it at your own pace.