TITAN Tricopter Part 3: Build and Fly!

Alright guys, the TITAN is complete and flying! Here are some of the last steps that I took to get it finished. A quick note on the pictures- I’ve been constantly refining the design so the pics are a bit inconsistent and there are some features I have added since these pics were taken.

If you haven’t seen the other parts then check out Pt1 and Pt2 in the related articles below.

Here is what I decided to do for the booms. My goal with this whole project is to make a tri that is as close to indestructible as possible. A lot of people use wood booms because they are cheap to replace, but I didn’t want to go through the hassle of replacing them every time I crashed. After doing some forum searching, I saw this method; A carbon fiber boom with a wood core.

This may seem like a strange combo, but it makes a lot of sense. Carbon fiber has very high tensile strength, but not very good compressive strength. If you have ever broken a hollow carbon fiber rod then you may have noticed that the normal failure mode is the inside of the bend crushes, while the outside of the bend remains relatively intact. This is due to the fact that when you bend a rod, the inside of the bend is under compressive load while the outside is under tensile load, a carbon fiber rod will fail on the inside of the bend first because it has less compressive strength. This is where the wood core comes in- wood has a much higher compressive strength, so when the boom is bent; the wood supports the interior of the carbon fiber and transfers a good deal of the compressive force from the inside of the bend to the outside where the carbon fiber can handle it as tensile force. The wood is also very light, so the combo of the two combines the best of both.

I used 10x10mm carbon booms with an 8.5mm hole in the center, this is the standard as far as I can tell. A 5/16” wood dowel fits perfectly with just enough clearance. I used Gorilla glue to bond the two- the reason for this is that Gorilla glue is a moisture cured urethane, meaning it can cure without air. This is important because the center portion of the boom is too far away from air for a solvent based glue to dry properly. Another reason is that Gorilla glue expands as it dries to fill any voids- plus it is super strong. I started by cutting my carbon to length (13”), then I cut the dowel about 4” longer so that it would fit all the way through with extra sticking out on both ends. I moistened the wood to activate the glue then I slathered the dowel, before I inserted the dowel into the carbon I placed a good pool of glue inside the carbon so the inside would be coated as the wood was pushed in.

Here you can see a couple of the booms left to dry, the one on the left has been sitting for about five minutes so the glue has started to expand. I used paper and masking tape to keep glue off of the outside of the carbon.

Here is a dried boom with the masking tape removed. You can see how the glue expanded to fill the space left by the masking tape. I think I over-moistened the wood because the glue expanded more than I expected.

Here is the end of the boom after the extra wood has been trimmed off and sanded. Looks good to me!

My motor mounts are designed to be held on only by zip-ties, however the carbon fiber is really slick and the mounts could slide off the ends pretty easily. I didn’t want to use foam tape to secure my motors because when the do eventually pop off in a crash I don’t want to have to get the old tape off before re-installing them. My solution to this is to slide a piece of silicone rubber tubing over the end of the boom- this gives a really grippy surface for the zip ties to grab on to and helps just a little with vibration dampening.

Here is a picture of the motor mount with a motor installed- not much too it.

I machined the standoffs for the electronics cover out of 3/8” delrin rod- here I am machining out the slots in the center to reduce weight.

Here are the completed standoffs.

The landing gear has been redesigned several times, I decided to add a vibration-isolated GoPro mount so I needed taller gear, then I was having issues with the frame oscillating with the yaw mech when it was on the ground. I solved this by adding a brace perpendicular to the gear- it really stiffens them up without adding much weight. The two parts are held together with two zip-ties.

Here you can see the tabs that interlock to stiffen the assembly up.

Cutting the frame out on the laser- I love the smell of laser cut plastic in the morning!

The pictures and video you see of the completed frame have an older design of the camera mount. I used vinyl tubing to suspend the platform below the frame- which worked really well for removing vibration, but it was a little too loose and wobbled in fast forward flight (you can see this in the video when the camera is looking back on the frame). The new design reduces the length of the tubing and places the battery under the platform- this is working excellent and I should have some pictures and video up soon to demonstrate.

Here are some pics of the yaw mech- very fast and VERY tough

The boom retainers have been working perfectly! They hold everything nice and tight but pop loose in a crash.

Here you can see what would happen in a side-on crash. The front booms can rotate forward and the back boom can rotate as well- absorbing energy.

Here is a pic of the underside, the camera mount can be installed or removed with 4 screws.

This thing is working great. I’ve crashed this thing over and over and haven’t had to replace anything but props. After about a dozen crashes (some very hard) I’ve only had to replace about $10 worth of parts! I’ve gotten such a positive response to the design that I decided to start selling the frames and components. I’m still putting together inventory but be sure to bookmark www.fortisairframes.com because the kits will be available in the next couple of weeks!

Here is a flight demo, more videos and articles will be coming soon- stay tuned!