May 06, 2012, 08:23 PM
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thechannelmast's Avatar


nice gyro rich
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May 07, 2012, 03:02 AM
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Fantastic job Rich, just the spur I needed to take a break from decorating and finish my Firefly!

Is the final mast angle as per your draft plan and can you advise where the C of G should be?

Cheers, Richard
May 07, 2012, 05:54 AM
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Originally Posted by beltec View Post
The HK heads arrived the other day, I was not impressed, so decided to make my own. I pinched 'Pete's' idea from the Cranefly log and made a head out of 10mm thick Polystyrene butchered from from a cutting board from the Pound Shop.

Polystyrene is not the easiest of material to work with, but it cuts OK with a normal woodworker's tenon saw and taps and drills OK with normal hand tools.

Quite pleased with the result - see picture below:
That's the same thoughts I had about the HK head, (that and I'm too tight to pay out for the carriage). That's an excellent version of Pete's head, could you post a photo taken on graph paper or next to a ruler so I can get an idea of scale? I will make some of these. I will try the chopping board, if that is not easy to machine then fine, if not I will use some Delrin (an acetal copolymer) which is easy to machine and has good mechanical properties.
May 07, 2012, 06:14 AM
It was a GLITCH! Honestly!
SafeLandings's Avatar
Yes it's as per the drawing regarding the angle of the mast, I will take some measurements later this afternoon when I finish work of my CG position. I can also take measurements of the rearward tilt, the roll is set in the neutral position as is the rudder.
The ride height as its sat on the ground is also to the plan, this works well as it helps with the old left roll on take off. Once the rotors are up to speed the tail just lifts up and gives a good indication that its ready for the air.

May 07, 2012, 07:39 AM
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OK Lazygit, thanks for you interest re the head. I'll post a PDF drawing this evening. I made a mistake about the chopping board material - I believe it is Polyethylene, not Polystyrene.

Yes, I thought the HK head looked somewhat delicate and would not stand up to the rigours of my landings (crashes!).

Cheers, Richard
May 07, 2012, 08:38 AM
It was a GLITCH! Honestly!
SafeLandings's Avatar
Originally Posted by britinoz View Post
G'day Rich.
I suggest that you have a look on ebay for ''2 X Bike Car valve caps flash light" I believe with a little modification that they may be very suitable for the rotors of your night flying project, and they wont cost you an arm and a leg to find out. They may even be suitable for day time use.
Found these, worth a play with I think?

May 07, 2012, 11:03 AM
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Herewith PDF showing dimensions of the 'Chopping Block' Rotor head. Easiest way to make is to use Rich's method of printing on paper, cut out shape and glue to the material and cut around the outline. It can be fabricated using simple hand tools, (saw, file, drill and M4 tap) - no special machining required.
Last edited by beltec; May 07, 2012 at 11:08 AM.
May 07, 2012, 11:34 AM
It was a GLITCH! Honestly!
SafeLandings's Avatar
Nice drawing

I have had a look at the Fire Fly and if you grip the fuselage between thumb and finger it balances on F2 (boom horizontal). The rearward tilt is 90 degrees to the front of the mast.
Hope this is of help?


May 07, 2012, 05:33 PM
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Thanks Beltec. I'm now glad I wasn't in too much hurry to get the HK offering. I'll see what polyprop is like for machining, and then have a look at Delrin. I have a piece of it around. with an additional hole parallel to the crossbar hole, but at the opposite end of the block, I could pin several blanks together and machine them all at once.

For the screw to the rotor shaft, is that just screwed downwards into the block? I was looking at using a stripped motor with a 1/8" shaft, have you used 4mm?
May 07, 2012, 07:46 PM
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britinoz's Avatar
On the Aus Ebay there is quite a big range of these units.Some having several Leds that give a variety of pattens ,and I believe that they are a lot cheaper than your UK Ebay.
My thought was to remove all excess material and then set them into the tip of the blade so they are captive and visible from top and bottom.
May 08, 2012, 03:11 AM
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LG - re rotor head.

Yes the rotor shaft just bolts straight down into the block - an M4 x 40mm cap screw in my case. I use two flanged ball bearings each side of the flapper plate, supported by two bell-motor mounts (see previous photo).
The plain shank of the cap screw lines up with the bearing inside diameters nicely.

For belt and braces, I counter-bored the underside of the rotor shaft M4 tapped hole and fitted a lock nut. If you are using a plain 1/8" motor shaft I guess you could just drill a 1/8" hole and fit a collar with grub screw in the counterbore to retain the shaft.

Sounds like you are lucky enough to have proper machining facilities, so you could go into mass-production I think Delrin would be preferable to Polyethylene as it is stronger and easier to machine, unfortunately the Pound Shop didn't have any!

Cheers, Richard
Last edited by beltec; May 08, 2012 at 03:19 AM.
May 09, 2012, 06:27 PM
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For making the fibreglass plates on the tail assembly (Ti and T2) I thought I'd make up some ply patterns, then cut the plates on a pin router. It took a while to cut the patterns accurately, and I needed more than one attempt, but when it comes to making the FG version it is only a few minutes for an accurate part. This approach will make it easy to reproduce the flapper plates for the rotor head too.

The pin router is a Proxxon drill in its stand, with a contiboard base screwed to the drill stand. I used a 1mm dia carbide cutter which I had bought in a job lot about 10 years ago. (See, it's good not to throw things out). The guide pin was a 3/4" moulding pin, tapped into the board, the head cut off and the top filed to about 1/16" high with the sharp edges removed with a needle file.

The Proxxon is far better than a Dremel, and well worth the extra cost (hmmm...., mine was second hand on ebay ) In use the cutter is lowered to be 1/32" above the pin, and dead in line. I taped a piece of wood to the stand column to act as a depth stop so the cutter was just clear of the pin. (Must get pic).
Last edited by Lazygit; May 10, 2012 at 12:13 AM.
May 10, 2012, 12:35 AM
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Here is the pattern for T2. Mine has a rectangular hole to fit on the boom which is 1/2" x 1/4" spruce as I didn't have any CF tube. I stuck a paper pattern on a piece of 1/16" ply (proper stuff, not light ply) and cut it to size. Mine is extended by 1/4" to fit the boom.

On the back of the ply I stuck a piece of thin double-sided tape. This is where ply is better for a pattern than plastic or metal as the tape is easier to remove so a new piece can be fitted to make the next one.

T2 and the tape is stuck on a piece of ply to test the cutting accuracy. The hole in the rectangle is to allow the hole to be positioned over the pin and the cutter to be lowered before cutting the boom hole.
May 10, 2012, 01:04 AM
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Ready to cut the hole and fitted over the boom. It took 3 mins including taking the photos to make an accurately fitting for the boom.

The next pic shows the finished T2 which took another 5 mins and the last pic shows the exersise repeated to produce the FG parts (still stuck to the ply patterns) and that took 20 mins. It would take only about 5 mins to make extras from this point as the 0.8mm FG sheet is much quicker to cut than the ply.

Rotor heads should be a breeze.
May 14, 2012, 11:28 AM
It was a GLITCH! Honestly!
SafeLandings's Avatar
Nice to meet you yesterday, those tail pieces you have machined out are really good in the flesh. Nice to see a bit of enginuity to better the design

I have made very little progress on my 'night flier Fire Fly' apart from mold the cowl from a trusty pop bottle.
Made a start on number 4 which is being built for a friend, I have altered the UC so it will be in 2 pieces. This is so that it can be broken down to post once it has been test flown etc May even make the mast removable just need to think how I can do this? Apart from that mod it really is no different to the white one I am flying at the moment. I am hoping to get that completed by the end of the week, maybe even both.



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