BD-5 microjet attempt - RC Groups
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Aug 21, 2004, 04:35 PM
Registered User

BD-5 microjet attempt


First, this is the first airplane I'm trying to built that is not a kit, and I have only minor experiance in airplanes at all. But reading through this forum makes you feel you're gaining everyons else experience (at least the theroretical one ). It seems more appropiet to post it here and not in the jet section because it's going to be powerd by one or two 6mm pager motors.
The whole thing started when I found out that a prop I've made for another project and didn't match 4mm motors, actually works great with 6mm motors in a duct-fun arrangment. The BD-5 is one of my favorite airplane, so I decided to try and make one. I've started from a rubber powerd plain I found in RcGroups, made by Nick De Carlis and scaled it down. The wing was scaled 50% to 9.3" and the body 40%. I've made a 3D solid view in a CAD program with some changes and procided from there. I took many pictures along the way. I'll post some, and any building remark will be apricieted. The main frame came up 5.5grams havy and has to be rebuilt, this time with lighter balsa and minor changes, and should end up around 2.5 -3 grams. This model I'm going to use for test flights with motor control only.
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Aug 21, 2004, 04:40 PM
Registered User
The duct fun has a 23mm prop and with a 6mm motor weights 2 grams. Thrust with 4.5 ohms motor is arround 2.5 - 3 grams, and with 3 ohms motor it's 2.5 to 3.5 grams.
Aug 21, 2004, 04:47 PM
Registered User
Wings panels and actually all the airframe were made from 0.5mm balsa ( which had to be machined from 1mm stock, was very hard to do ). That balsa, I know now, was one of the haviest that can be found. I now already have balsa that is one fourth lighter and that was also custom cut at the supplier down to 0.45-0.5mm and also down to 0.3-0.25mm.
Aug 21, 2004, 04:55 PM
Registered User
In making the main frame I use flat panels. I had hard time trying to hand carve the nose cone and gave up trying and CNC machined it from four sheets of balsa glued together. I had to use it again for making mold for vacumed forming the canopy.
Aug 21, 2004, 05:06 PM
Registered User
And the final result : 5.5 grams havy main frame & canopy + 2 grams Duct-Fun + 1.9 grams 60mah lithume + 2.4 grams JMP combo receiver + wires and some wood for positiong stuff. Came out to 13.6 grams.
Next, I'm going to add another Duct-Fun side by side and see how it goes. Right now it has marginal thrust for flying, and it's actually more like an extended glide with the power on. I had bad wind condition when I tested it.
I'll continue next week and update.
Aug 21, 2004, 06:36 PM
Sticky Shepherd
Graham Stabler's Avatar
Amazing work, the fan unit is fantastic. It looks like steriolithography!!

Wow, hope it works out!!


I still want details of your CNC set up!!
Aug 21, 2004, 07:58 PM
Frequent Poster
Pete P.'s Avatar
I agree!!! Very nice!!! How did you make the Duct Fan cowl and blade? I love the BD-5!!
Aug 22, 2004, 12:14 AM
devilscries's Avatar
wow nice fan, and that small of a jet should look insane when its done. im very impressed. drool
Aug 22, 2004, 12:46 AM
zoidburg! (\/)(;,;)(\/)
kase_kopf's Avatar
wow that is amasing looks great, i about did a back flip
Aug 22, 2004, 01:32 AM
Fly it like you stole it..
Tram's Avatar
Ohh now that rocks!
Aug 22, 2004, 04:05 AM
Registered User
The machine is basically the Wabco 1200 German made milling machine. Through their dealler in my country I orderd it with some upgrades. The main motor is 2KW and turns the spindle from 0 to 7000 RPM. The table is 200 X 700 mm and can travel 250mm x 500mm ( vs 200 x 500 on a standard model ). It was orderd with ball screws installed, timming pullys, and manual hand wheels ( I wanted to be able using it manually as well). I also add a re-enforcing back plate to the vertical column for added ridgety. I retroffited the machine for CNC operation myself. The motors are 2NxM API brushless servo motor ( API compony was since taken over by another compony which no longer makes this motor ). The controller is made from JRKERR 3ph motion control & driver cards and the software a free example by JRKERR for making a 3 axis milling machine. The softwear has everything you could ever want in a prototyping machine. It also gives the option to free the motors and works manually ( and get x y z digital readings ). I'd recomand it to anyone. For a small machine such as Sherline and using brushed pitman servo motors you can get away with only 1000$ for the retrofit. I've spend about 4000$ on it becouse of the big motors I've used, and the wabco machine with all it's upgrades and a cooling system costs around 8000$. The program for generating G codes is Master Cam.
Aug 22, 2004, 07:36 AM
Sticky Shepherd
Graham Stabler's Avatar
Nice, we have a Wabco in my department. Unfortunately it was CNCed by wabco. It uses stepper motors with step and direction which would be fine if each axis had it's own direction pin :O

I have all the parts collected for a serious CNC router now, THK bearings, ballscrews etc. Seriously considering servos and geckodrives but will check out JRKERR more carefully.


sorry this is off topic really
Aug 22, 2004, 09:24 AM
Registered User
beanoman's Avatar
woah thats reallllllly nice

i can only make stick planes and BUMPs

Aug 22, 2004, 12:12 PM
Thanks for the Fish!
aerogel's Avatar
Very Kewl have you Tried to Tweak The Fan any to get more Thrust

Aug 22, 2004, 01:12 PM
Frequent Poster
Pete P.'s Avatar
Is your cowl right above the canopy? You might want to make it a tad more aerodynamic. I'm sure that'll improve thrust a tad. Also, have you tried a 7mm Duct-fan? Sorry if it seems like i ask 'have you...7mm...?' alot, it's just that I'm very interested in them :-)

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