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BumbleDrone 3000


Senior Member
BumbleDrone 3000 (a Delrin "Pro Tricopter v1.2" build)

Hi all!

I stumbled on flitetest a week ago and was instantly hooked. I've been flying scale planes for 20+ years and helis for about 6 now and this content is exactly my genre. I've seen many multi-rotor craft on youtube etc, but had never seen a tricopter before, or maybe I had but it didn't registered at the time what it was specifically. I came across the episode with David Windestål and his tri and was instantly infatuated with the concept of a multi rotor craft with mechanical yaw. Within a few hours I had seen enough, and ordered up the fpvmanuals.com "v1.2 Pro Tricopter Delrin Kit".

Well to my surprise today I found it in my mailbox, and I have to admit I'm super excited to get started!


Off to HomeDepot to check out their square dowel stock...
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Flitetest has got me interested in tricopters as well and have often wondered how hard they are to fly. I will be keeping an eye on this thread. Good Luck and definitly keep us informed of how it goes.


Senior Member
would like to know how this kit stacks up. i have been looking at these for a while now and cant quite bring my self to spend the money :)


Senior Member
Getting acquainted with the kit and taking inventory, pretty straight forward.

Down the left we see a foam strip, the motor mount plates and stanchions, center we see the hardware baggy and reinforcement parts, and finally right we see the bamboo tray, main frame and electronics shield.


Interesting to note is how this is all laser cut, you can actually see burns on the edge of all the protective self adhesive warping on the delrin and also the edge of the bamboo is blackened up pretty good too.

All the cut pieces need to be dealt with like most any model kit, the pieces need to be separated/removed from each other, and all the little extra production scrap bits removed. Every little rectangle and circle you see is a little piece of delrin that needs to be removed. I found it easiest to take a #00 phillips and just "punch" them all out into a little pile (some will almost fall out, some will need a good push). There are some also that make their way out during shipment and will be loose in the main baggy, I collected those and put them in the pile so as not to confuse them with "real" parts later on as I haven't yet dug into the hardware baggy.


The large "square" of delrin reinforcement parts has laser cut outlines on one side, and the other side is an uncut sheet. Each piece just "pops" away from the others and peels off the back sheet. Some scrap bits will stay attached to the back sheet, and the rest need to be pushed out with the #00 phillips as previous.


After some work you end up with this collection. At this point I wouldn't throw anything away from the "scrap" pile, some parts can look like scrap and vice versa. Better safe than sorry! For now I've left all the protective coverings on the parts, and will just be removing them as needed during assembly. Also worth note here is that one side of all the delrin parts has a "cleaner" side than the other. The bottom of the part during cutting gets a little "slag" build up and is not as finished looking. You will want to always consider which side of the part is "viewable" and hide the rougher side when possible during assembly.


According to the instructions, here's what we're looking at:

A - 2 Main Delrin Plates
B - 4 Regular Motor Mount Plates
C - 2 Yaw Motor Mount Plates
D - 1 Yaw side plate
E - 1 Yaw side "L" shape plate Servo Holder
F - 1 Yaw top plate
G - 1 Yaw bottom plate (with 3 slots)
H - 1 Servo bracket
I - 2 Axle holders
J - 1 Yaw motor mount vertical plate
K - 1 Yaw motor mount vertical plate with servo horn
L - 1 Jig (Delrin)
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Senior Member
So now we've got a nice little pile of parts, let's get some assembly done!

The manual says to start with the yaw axle, so grab 2 "Axle holders" from your delrin pile and 1 "Yaw Axle" from the hardware bag:


From there it says you want to use an exacto knife to put a chamfer on the inside edge of one of the holes. That seems a little clumsy to me, and I chose to use a drill bit to do the job. I imagine they want people using a knife to absolutely preclude the possibility they will just ream out the hole accidentally instead of adding a chamfer. So note here, DO NOT USE A DRILL BIT TO REAM OUT THE HOLE. It is supposed to be a very tight fit.

The "Yaw Axle" itself is 3.1mm OD, so I chose to use a 5/32 drill bit which measures out to 3.9mm OD. Holding the bit with just my fingers I very lightly pressed the bit against the Axle Holder and spun the bit a few times to create a very small chamfer (beveled edge) on the inside edge as seen here. This literally took two seconds and a very light spin, don't get carried away here!


Now take the Yaw Axle and place it against the chamfer with your hands, keeping it at a 90* angle to the Axle Holder. With a small hammer slowly tap the axle into the Axle Holder. It helps to have a surface underneath that will give a little and let the axle penetrate out the other end allowing it to "cut" it's way through the Axle Holder. If you hammer against a hard surface you will notice that the Yaw Axle pushes some delrin out the other end and stops once it binds up against the surface as the excess has nowhere to go. You might also need to scrape some of this excess off the end once the Yaw Axle has pushed through to clean it up. Repeat the process so it looks like this.


Grab an 1/8″ Axle Collar from the hardware bag. Note that in my kit, all the little black set screws for the Axle Collars were loose in the bag and I had to hunt for them. Put a dab of loctite on the set screw and screw it part way into the Axle Collar. Leave about 1" of the Yaw Axle protruding through the Axle Holder, and slip the Axle Collar onto the Yaw Axle. With the Yaw Axle up against something like the edge of the work bench (so the Collar doesn't slip off) slowly push the Axle Holder towards the end of the Yaw Axle until only about .5mm of the Yaw Axle is showing through the Axle Collar. Making sure the Axle Collar is firmly against the Axle Holder, tighten the set screw.


Take the Yaw Bottom Plate (part G above, three holes) and spacing the "other" Axle Holder as needed, assemble the Axle Holders into the Yaw Bottom Plate leaving one hole in between the two Axle Holders. Then take the Yaw Top Plate and slip it onto the assembly. It should look like this when done.


Get the Yaw Side Plate (L shaped) and your Servo Bracket. Take the Yaw Side Plate and lay it flat on the bench so that the two centered holes are to your left and the part with the two centered rectangles is facing down towards you. Take the Yaw Axle assembly and insert it down into the Yaw Side Plate making sure that the side with the third hole (part G above) faces down towards you.


Take the Servo Bracket, and with it orientated so that the "hooks" face up away from you insert with two motions. #1 slip it into the two rectangle slots in the Yaw Side Plate. #2 very slowly and carefully slide the Servo Bracket upwards into the Yaw Axle assembly. BE CAREFUL! This piece takes finesse to get inserted, not force. If it does not slip up/in, very easily bend the assembly around until the holes line up and it goes in. Again, this does not take any force, if you have to use force it's not lined up correctly. Be patient.


Next take the Yaw Top Plate and cap off the assembly, and slip the 1/4 ” nylon spacer onto the axle.


Your Yaw Axle housing is now complete!
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Senior Member
Now onto the Yaw Motor Mount assembly.

Grab your "Yaw Motor Mount Vertical Plate", "Yaw Motor Mount Vertical Plate w/ Servo Horn", and two bearings from the hardware bag.


More chamfering! As before I'm going to use a drill bit to do this work as it's easy, even and fast. As before I'm going to warn you to NOT ream out these holes with the drill bit, but to only bevel the edge enough to allow the bearing to slip in with a little force. Ok we're clear here, chamfer - not ream, right?

The ID of the bearing holes are about 6.3mm. A 5/16th bit works nicely here measuring at 7.9MM OD. Same process as before, using just the bit in your fingers lightly and swiftly spin the bit against the hole and it will cut out a nice bevel. Don't push to hard, don't cut too much out, just a simple little chamfer to get the bearing started.


Time to insert the bearings. We need to be careful here not to damage them, i.e. we don't wait to hit the bearings with anything metal, and we don't want to hit them against anything metal (here by using the nylon cutting board). Note here also that the bearings have effectively a top (flanged) and a bottom. The Narrow end of the bearing is what we're inserting into the mounts. Placing the motor mount plates chamfer up, center the bearings in the holes, and use the "Jig" (part L above) to cover the bearing. Once sure that the bearing is still centered and the Jig flat, lightly tap the Jig with a small hammer until the bearing seats into the mounts. The key here is lightly, the delrin being soft, if you hit the bearing too hard it will actually start to cut into the mount and ruin it. Just nice light taps are all you need.



Next take a Yaw Motor Mount Plate and slip the vertical plates into it as shown here with the bearing flanges facing outward, or opposing each other. Once those are seated correctly, cap it off with the remaining Yaw Motor Mount Plate.



Take the second 1/8″ collar out of the hardware bag, find its set screw, apply some loctite to the set screw, and thread into the collar a bit. Place the Yaw Motor Mount onto the Yaw Axle (making sure the nylon spacer is still on the Yaw Axle), slip the collar onto the end of the Yaw Axle, push the assembly together to eliminate any slop, and tighten the collar. I noted here that my set screw was a bit too long and contacts the delrin Yaw Motor Mount plates not allowing them to spin freely 360*. The contact is so minimal that just spinning it around for a little bit will wear some delrin off and it will "self clearance", I might also hit it with a file and take it down a bit.

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Senior Member
The kit is designed for 10mm booms, which I couldn't source locally. I went over to HomeDepot and found they sell 3/8" square dowel stock in 36" lengths for $.98 each, hard to beat that. 3/8" works out to 9.5mm (which in reality measures out to 9.6mm). Not ideal as I notice that the booms have just the slightest play in them when inserted into the motor assemblies, but we'll see where I end up once I've got them all mounted up tight (easy enough to slip a shim in there).


Boom length was decided for me at HomeDepot and I didn't even know it. The dowels being 36", and me wanting to be efficient, I just decided to chop them in half at 18". The kit calls for the rear boom to be 3" shorter than the front two, so I ended up with two sets of booms consisting of 18" front's and 15" rears for $2.94.

All cut up and off to paint they go!

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Multi-rotor madman
The kit is designed for 10mm booms, which I couldn't source locally. I went over to HomeDepot and found they sell 3/8" square dowel stock in 36" lengths for $.98 each, hard to beat that. 3/8" works out to 9.5mm (which in reality measures out to 9.6mm). Not ideal as I notice that the booms have just the slightest play in them when inserted into the motor assemblies, but we'll see where I end up once I've got them all mounted up tight (easy enough to slip a shim in there).

View attachment 3828

Boom length was decided for me at HomeDepot and I didn't even know it. The dowels being 36", and me wanting to be efficient, I just decided to chop them in half at 18". The kit calls for the rear boom to be 3" shorter than the front two, so I ended up with two sets of booms consisting of 18" front's and 15" rears for $2.94.

All cut up and off to paint they go!

View attachment 3829

Looks like you got your calipers at Harbor Freight......did you? (I got the EXACT same pair, picked them up at Harbor for like 10 bucks. :)

Good Stuff!



Senior Member
With the paint dry, time to start on the booms.

Take the Jig and line it up with the end of the dowel. Using the hole, mark the spot to drill for the pivot bolt, and drill it out with an 1/8″ drill bit. I drilled out the Jig to allow for my auto punch to fit, it comes with a hole to be used with a pin to mark center though.



Now take the Jig and use it to mark the motor mount ends of the front booms. Mark the side notches closest to each other with the single notch towards the end of the boom. Make sure you mark on the sides of the boom, whereas you drilled on the top/bottom sides.


Notch just enough wood out so that the nylon screws fit nice and snug, and then assemble the mount.



Front booms are now complete(ish).
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Senior Member
The rear boom is pretty simple, just slip the boom into the yaw housing as far as it will go, mark the boom using the front two holes, drill them out with a 1/8th inch bit, and use the remaining three nylon screws to complete the assembly (the 3rd screw goes in the hole just behind the servo). This is also a good point to drop in the two small metal screws / nuts (w/ loctite) that hold the front of the rear motor mount together. Don't forget these or the rear motor might depart the aircraft during flight. ;)


Take the Jig and mark the back sides of the tail boom as we did with the fronts, but use the marks farthest apart from each other this time, then notch them out as before.
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Senior Member
The body is a little tricky, I tried to put it together by just looking at the pics and I had to do it about 4 times before I got the right order...

Take the top delrin body piece with the "U" out front, and attach four tall male/female standoffs, two small standoffs and two nylon nuts as shown.


Then take the bottom body piece with the three ovals and key it onto the two front short standoffs. Slip the rear boom in between and clamp the two parts together using mylon nuts for the front two posts and four of the large steel screws and nyloc nuts to clamp the rear boom.



Take each front boom and slip it between the body pieces, insert a large steel pivot bolt, and two more steel bolts towards the edge to hold them in place. Now you should have something that finally looks like a tricopter!



For the bamboo tray, get four long black standoffs, the four long nylon screws, and four nylon nuts. Assemble as shown.


Finally drop the colored cover on the top, hold it down with 4 nylon screws and major assembly is complete. Eventually you will want to loctite these nylon screw / nuts as they will rattle loose during flight otherwise. I waited until I was ready for my maiden flight in case I had to take any of the hub apart during the rest of the build for wiring etc. Don't forget this though, they need loctite.


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Senior Member
Here are some daylight pics with the stanchions installed. I put the front two behind the booms so on impact they would just roll back and hopefully just break the zip tie instead of binding and cracking.

2012-04-18 13.46.46.jpg

2012-04-18 13.48.07.jpg
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Senior Member
So now we play the waiting game for parts to arrive.

I decided to go with some NX-4008 motors and Turnigy Plush 18A ESCs per build recommendations I've read. Those were each out of stock at HK, but fpvmanuals had them according to the site and I've got 3x each on the way. A few more bucks from them, but hey in stock, shipped out of the US, and it's nice to support them since they do make the darn thing. The NX-4008 motors actually have a pretty mixed review from HK customers on their site, but having no experience with multi-rotor craft it's just one big experiment I guess so I grabbed them.

I did notice that one has to be pretty careful what they buy from HK. At one point I had my cart all set up, and was looking at $50 in shipping charges. I soon realized getting large Lipos from HK is spendy in a different way and from the reviews I've read, shipping times are hit or miss with some people waiting months for Swiss post to get on with it. Decided to just grab a Lipo from the LHS for now. For a controller I'm just getting a cheap multi board and programmer from HK, seems to get fine reviews. I did splurge and go with genuine GWS props after seeings some vids of people losing tri's into lakes from fatigued cheapo props cracking mid flight. Maybe it doesn't matter, but gives me the feel good to get them.

Some product shots from the HK site:

17924(2)[1].jpg TR-P18A[1].jpg QUAD_CON32K_MAIN%281%29[1].jpg P-RD-1047[1].jpg


Senior Member
Looks like I am going to end up with HK batteries after all. In your cart you can't mix warehouse products, so I just made a second order for the batteries out of the US warehouse. Picked up a couple 3300mAh 4S Turnigys.



Senior Member
Love package delivery day! Motors from fpvmanuals.com showed up today. A nice touch, they had the proper bolts and lock washers to mount to the pro tricopter kit. The kit itself comes with some short black standoffs to take up the space in between the motor mount arms. Just use a needle nose to hold each in place, drop some loctite on each bolt and thread it up into the back of the motor till it's snug. Delrin isn't indestructible, so be careful you don't go too tight. I decided to go with the front two facing down for clean airflow, the rear would interact with the servo mechanism so unless I rebuilt it upside down it's just going to be upright for now. I have to admit too I mounted them facing down just because it also looks pretty cool that way. We'll see how many props I go through before I change my mind on that one! Current weight is about 1.2 pounds (base kit + motors).


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