Cox TD .010 Ply Rolled Fuselage 3Ch Speeder
#176
Thread Starter
If you follow the leading edge of the horizontal stab there is no trim in the elevator the elevator is not tapered but the stab is foiled from the front to the hinge line. Wedge shape for positive solid wing hold when tracking a line and with the elevator squared off reduces losses. The flight test on Sunday had the .020 with the cg on the money the plane tracts straight and level on power and in glide its fast and hangs well.
Yes 20w IC isn't much to work with power wise but you can take advantage of its low 14g weight and so far has been enjoyable to use.
The 40w engine has plenty to power this 53 Sq/in wing - could do 40 sq/in and still grease it in without too much fuss if stuck going downwind.
The fuselage has plenty of beef to support the TD .020 power and weight makes a good match to this plane.
Yes 20w IC isn't much to work with power wise but you can take advantage of its low 14g weight and so far has been enjoyable to use.
The 40w engine has plenty to power this 53 Sq/in wing - could do 40 sq/in and still grease it in without too much fuss if stuck going downwind.
The fuselage has plenty of beef to support the TD .020 power and weight makes a good match to this plane.
#177
The new sheet wing on my GLH is only about 64 sq/in and it glides fine. The built up wing was a piece of cake to land. If I ever get the time I think I'll do another built up one as I think I can get lighter still. I just really have to be in the right mood to mess with toothpicks that size. Once you get below 1/4" thick it gets tough. I just cut twice as many ribs as I needed as I broke half of them building it.
I have one of the aluminum backplates from e-bay (ridenfligh) and it works well and saves running new holes if the firewall was setup already. I have learned that you need to bolt the engines on at this size, not screws, to get past the vibration barrier.
I have one of the aluminum backplates from e-bay (ridenfligh) and it works well and saves running new holes if the firewall was setup already. I have learned that you need to bolt the engines on at this size, not screws, to get past the vibration barrier.
#178
Senior Member
My Feedback: (3)
I just use #2 socket head sheet metal screws for all .049 - .061 stuff, but I use at least 5/32" to 3/16" plywood firewalls for the high powered engines. 1/8" plywood is marginal.
Same goes for beam mounted TDs on the black plastic mounts. Machine screws and blind nuts gave me more trouble and a fellow flyer talked me out of using them for 1/2A projects years ago.
With a Cyclon or Fora backplate mount, using machine screws and blind nuts would force you to use a firewall that is larger than the backplate, creating more frontal area.
I use a #43 pilot drill for the #2 sheet metal screws. The drill bit needs a few winds of tape so that a typical drill chuck will grip it.
Same goes for beam mounted TDs on the black plastic mounts. Machine screws and blind nuts gave me more trouble and a fellow flyer talked me out of using them for 1/2A projects years ago.
With a Cyclon or Fora backplate mount, using machine screws and blind nuts would force you to use a firewall that is larger than the backplate, creating more frontal area.
I use a #43 pilot drill for the #2 sheet metal screws. The drill bit needs a few winds of tape so that a typical drill chuck will grip it.
Last edited by combatpigg; 06-06-2014 at 08:22 PM.
#179
It's not the power that is the issue. The 020 TD sets up an occilation in the 22k to 23k range that becomes a brick wall holding the rpm down. Even mounting it on a piece of pergo on the test stand and pre-drilling the screws I ran into this. I could take the same motor and bolt it in and pick up 2-3k or more. Could be why cox propped it with the 4.5 X 2 prop and keep the rpms down.
#180
Senior Member
My Feedback: (3)
Has this engine had the piston lightened..?
I'm no mechanical engineer, but it seems that the smaller you go in engine size the more smooth [intrinsically] it ought to be at higher revs.
I've heard of tinkerers using out of balance props to diagnose whether the piston is too heavy or too light by doing short trial runs. According to Clarence Lee a steel piston model plane engine is usually going to be heavy on the piston side once you reach a high enough rpm to reveal that.
I took a bunch of weight out of several .049 pistons and felt that was always a win - win to improve smoothness and increase the red line and longevity. With the load carried by the piston dome, you can make the walls as thin as paper..or as thin as you dare.
I'm no mechanical engineer, but it seems that the smaller you go in engine size the more smooth [intrinsically] it ought to be at higher revs.
I've heard of tinkerers using out of balance props to diagnose whether the piston is too heavy or too light by doing short trial runs. According to Clarence Lee a steel piston model plane engine is usually going to be heavy on the piston side once you reach a high enough rpm to reveal that.
I took a bunch of weight out of several .049 pistons and felt that was always a win - win to improve smoothness and increase the red line and longevity. With the load carried by the piston dome, you can make the walls as thin as paper..or as thin as you dare.
#181
Thread Starter
I used Mikes -ebay .020 aluminum mount with 2 peewee caskets and two allen head screws through 1/16th thick firewall. A trick I do after the threads are cut in the wood I saturate them with thin hot CA to allow some gusto once ready to mount the engine. In my case I had to drill two holes in the aluminum mount as 3 of the 4 tabs needed to be removed to match up to the .010 firewall. It worked out great the .020 mount dia is a close match for the .010 dia and its two mounting holes. Mikes mount allows upgrading any .010 size firewall.
#182
Thread Starter
My bladder is old and needs the surgical tubing replaced the pressure fades a bit much causing lean outs mid way through the run.. so I fabricated a micro size fuel tank that could yield some reasonable run time and fit within this small airframes fuel bay. I had used a modern 1oz tank as my inspiration for the mid size 3/4 oz tank as a step down for a .049 and now with some help from a cork a .020 tank perhaps a 1/2oz. very light only 5.3g I plan to tap the engine shown for crank case pressure. The void in the back plate will be filled halfway with some epoxy then drilled and tapped giving the pressure nipple plenty of bite. I hope to be able to taxi / take off with this set up with the bladder the exhaust throttle would allow the engine to load up a bit. Perhaps this will be more consistent through the power band using this wee lil hard tank a perfect size for great duration with the .010. and perhaps 4 mins. with a some throttle play using the TD .020 will see how it goes.
#183
Thread Starter
Managed to get a better fly by pic today at the field.
And here is a vid with the 3.3 x 3.15 prop using a perfect brand tin tank no pressure tap.
Average good passes at 25.4k and 26.557K rpm on the best pass theoretical speed 79.22 mph
https://www.youtube.com/watch?v=ZM2cn0mdHx4&feature=youtu.be
And here is a vid with the 3.3 x 3.15 prop using a perfect brand tin tank no pressure tap.
Average good passes at 25.4k and 26.557K rpm on the best pass theoretical speed 79.22 mph
https://www.youtube.com/watch?v=ZM2cn0mdHx4&feature=youtu.be
#185
Thread Starter
The stock TD .020 with that brand prop does allows it to unload at the expense of some thrust being only 3.3in dia. Steep dives do scream with the 3.15 pitch with enough load to keep in a safe rpm range at least thus far for the engine.
The posted footage was done keeping things more level on the passes by the cam. Its tough to radar this one I need assistance or learn to deal with it with a quick left handed read. I feel stuck on the sticks at all times do to size. Downwind leveled off that day was with a 8-10 mph winds looks like upper 60's. Cross wind looks to be in the mid 50's. Temp was 87 deg, with 25% nitro. No way will I get 80 out of this one.
What has been learned based on the design;
Need the engine mods,
reduction in span (17in)
trim down the tail feathers,
rolled fuselage with a nose to cowl the engine
Could get 80 mph level flight with a 3 x 3.5 pitch at 29k. gives you 96.2 mph /16 mph drag loss which is still wishful thinking to see 80.
On the bright side its the fastest 3ch stock TD .020 I have ever flown or observed.
The posted footage was done keeping things more level on the passes by the cam. Its tough to radar this one I need assistance or learn to deal with it with a quick left handed read. I feel stuck on the sticks at all times do to size. Downwind leveled off that day was with a 8-10 mph winds looks like upper 60's. Cross wind looks to be in the mid 50's. Temp was 87 deg, with 25% nitro. No way will I get 80 out of this one.
What has been learned based on the design;
Need the engine mods,
reduction in span (17in)
trim down the tail feathers,
rolled fuselage with a nose to cowl the engine
Could get 80 mph level flight with a 3 x 3.5 pitch at 29k. gives you 96.2 mph /16 mph drag loss which is still wishful thinking to see 80.
On the bright side its the fastest 3ch stock TD .020 I have ever flown or observed.
#186
Thread Starter
Updates the steel tank only provides around 2 min 40 secs of run time which just doesn't give me enough flying, Being spoiled over the years with much more duration its frustrating to hear the engine crackle lack and stop abruptly. The bladder tank ended up pushing too much pressure to the engine and needs a restrictor fitting. It looks like the effort making the bottle tank has paid off I now get just under 6 mins and allows me to land at idle after a satisfying flight rather than forced down by an empty tank. Using a Cox Lil Stinker 4 x 2.5 prop gives me enough thrust to climb out vertical.
#187
Senior Member
My Feedback: (3)
It sure is nice not to deal with bladders unless you really see no better solution.
They have many faults, but one of the worst is they can't ramp up fuel delivery based on demand like crankcase pressure [or tuned pipe pressure] can.
A really neat device to "tame" bladders is a diaphram actuated check valve that operates off of crankcase pulses. It's almost like having timed fuel injection. It broadens the needle like you wouldn't believe. A local flyer / machinist used to make them for .36 Combat engines. They tuck right inside the recessed rear cover of the engine. Fuel can't pass through them unless the prop is turning, so they also cure accidental flooding.
They have many faults, but one of the worst is they can't ramp up fuel delivery based on demand like crankcase pressure [or tuned pipe pressure] can.
A really neat device to "tame" bladders is a diaphram actuated check valve that operates off of crankcase pulses. It's almost like having timed fuel injection. It broadens the needle like you wouldn't believe. A local flyer / machinist used to make them for .36 Combat engines. They tuck right inside the recessed rear cover of the engine. Fuel can't pass through them unless the prop is turning, so they also cure accidental flooding.
Last edited by combatpigg; 06-30-2014 at 11:24 PM.
#188
Thread Starter
I read a thread you and a few folks were trying with the bladder inside a hard tank with pressure collapsing the bladder good idea for steady feed.
Back in the day we had a diaphragm type pump using the engine cycle to feed fuel nice and predictable and would monitor the flow as demanded just not practicable to fabricate a micro version for most folks.
Yes I tried a few tricks even tapped and put a pressure nipple on the back plate but the pressure was too great the nipple was allowing too much into the tank and setting the needle was fussy fussy. Going to the clunk tank with just a breather tube seems to be giving me predictable runs each time the trick is to lean out a hair on the ground as air rams into the vent tube at speed pushing more fuel. I need a smaller hole in the nipple to use crank case pressure the nipples I had bought have too much ID so maybe install a inline metal tube to pinch down to just allow a tad in. The one way valve holds pressure allowing it to build up in the tank and the wee engine responds to this quickly richening up so really need a muffler with a tap perhaps. I bought a G-Mark .030 for 75 bucks from Tim to try on this plane its in the mail at the moment comes with a nice lil RC carb and muffler I can tap for pressure. May save that engine for another project will see how it goes haven't given up on the crank case pressure yet just need to fab up a restrictor tube next. I want every last drop of fuel pushed out of the tank to allow acro even when the tank is down to 15% fuel.
Back in the day we had a diaphragm type pump using the engine cycle to feed fuel nice and predictable and would monitor the flow as demanded just not practicable to fabricate a micro version for most folks.
Yes I tried a few tricks even tapped and put a pressure nipple on the back plate but the pressure was too great the nipple was allowing too much into the tank and setting the needle was fussy fussy. Going to the clunk tank with just a breather tube seems to be giving me predictable runs each time the trick is to lean out a hair on the ground as air rams into the vent tube at speed pushing more fuel. I need a smaller hole in the nipple to use crank case pressure the nipples I had bought have too much ID so maybe install a inline metal tube to pinch down to just allow a tad in. The one way valve holds pressure allowing it to build up in the tank and the wee engine responds to this quickly richening up so really need a muffler with a tap perhaps. I bought a G-Mark .030 for 75 bucks from Tim to try on this plane its in the mail at the moment comes with a nice lil RC carb and muffler I can tap for pressure. May save that engine for another project will see how it goes haven't given up on the crank case pressure yet just need to fab up a restrictor tube next. I want every last drop of fuel pushed out of the tank to allow acro even when the tank is down to 15% fuel.
#189
Senior Member
Join Date: Jan 2003
Location: Spring Hill,
FL
Posts: 4,734
Likes: 0
Received 0 Likes
on
0 Posts
If the nipple is brass or a metal you can solder you can just use telescoping brass tube to fill the nipple until it's the size you want. The K&S stuff works well for things like this. I've done it for a couple things that I don't remember but it wasn't for an engine. Basically I just coated all the pieces with non-corrosive flux, then slid all the brass together and used micro torch to flow solder in. It will flow between the tubes. It doesn't need to be air-tight because they go inside the nipple and when the fuel tube goes on it's all contained.
Edit: Of course if you have some brass rod you could just solder it in place and drill it to whatever size you want.
Edit: Of course if you have some brass rod you could just solder it in place and drill it to whatever size you want.
#190
Senior Member
My Feedback: (3)
PS.....You don't normally use a check valve in the pressure line, do you..?
It WILL build excess pressure that is hard to control.
If you can get great runs without any gimmicks or gizmos, that's all that counts. You would need to be a swiss watch maker to build a backplate mounted pump for a .020..!
It WILL build excess pressure that is hard to control.
If you can get great runs without any gimmicks or gizmos, that's all that counts. You would need to be a swiss watch maker to build a backplate mounted pump for a .020..!
#192
Thread Starter
Yea I have the .061 it required a few rich tanks of all caster blend to break in and come alive they just don't scream like a TD but will make good torque. I have read the .030 will put out about the same power as a .020 with torque again being the advantage over a drop in rpm. Having a RC carb and muffler was why I bought the engine perhaps may make a great sports engine for acro flying if tapped for pressure with a clunk tank.
Lol I tried it without a check valve and the nipple being bored to used as a muffler tap was causing the engine to run rich also thought perhaps with a fuel tank I was back feeding fuel into the crank so tried a check valve and the pressure was too much so looks like the only fix is to source a small nipple with a pinhole with no check valve or leave the nipple alone or fill it up with epoxy with a oiled soaked needle in the center and wiggle it out after its set enough to maintain form orrrr a bit of aluminum tube inline with the pressure line to crimp down to reduce the pressure to just enough to help push fuel when flopping about. With a .020 it doesn't take much tank pressure at all to motivate steady fuel flow in the air. Cafeenmans idea with a rod would work if I had a small enough drill bit ok just remembered I have some red plastic tube from a WD40 can that uses a pinhole size extension will try putting that inline tonight no tube crimping needed or buying another nipple.
Thanks gents you all made me think
Lol I tried it without a check valve and the nipple being bored to used as a muffler tap was causing the engine to run rich also thought perhaps with a fuel tank I was back feeding fuel into the crank so tried a check valve and the pressure was too much so looks like the only fix is to source a small nipple with a pinhole with no check valve or leave the nipple alone or fill it up with epoxy with a oiled soaked needle in the center and wiggle it out after its set enough to maintain form orrrr a bit of aluminum tube inline with the pressure line to crimp down to reduce the pressure to just enough to help push fuel when flopping about. With a .020 it doesn't take much tank pressure at all to motivate steady fuel flow in the air. Cafeenmans idea with a rod would work if I had a small enough drill bit ok just remembered I have some red plastic tube from a WD40 can that uses a pinhole size extension will try putting that inline tonight no tube crimping needed or buying another nipple.
Thanks gents you all made me think
#193
Thread Starter
Ok tried some of the red spray tube from the WD40 about a inch and it worked but pushes the fuel faster allowing more power leaner settings but gobbles up the fuel and reduces run time on the bench will see if the extra power in the air is worth the loss in run time. Cut it down to about 3 mins 25 seconds from 5 mins 45secs.
#194
For the Tee Dee .049 backplate pressure, we used a pressure fitting soldered right up closed, with a piece of wire going through. The wire was waxed or oiled so it could be removed easily. The rule of the time was the same size wire as you would fly with. (control line) I used .009" in the TD and .015" in the Rossi/Supertiger .15's for Goodyear. I had/have about a mile of .009" wire. Maybe .006" would be suitable for your .020 or .010 TD. The pressure regulator sounds like a nice device. I think there was a guy flying combat on the weekend from Detroit I believe, with one of those. Wonder where you get them, or how to make them. Maybe they are the same as the RC ones, Cline or Perry or whatever? I have never seen anyone use one here for rc that I am aware of. Nevertheless, if the motor works fine on suction, I would just use that. If the carb is bored out way too much to run on suction, then pressure is needed. Otherwise it is just a source of problems from air leaks or bladders blowing up in your face. A limp balloon tank may work too on suction.
#195
Thread Starter
Should be interesting to find the best setup for a mix of duration and power. .030 came in the mail thanks to Tim!
-43.9g .030 with throttle and available muffler pressure
-39.3g .030 back plate no muffler
-29.4g .020 with throttle
-25.1g .020 no throttle -added muffler / pressure
Note if you try using the muffler with the .020 it will not work with a pee wee tank as is would need to be cut for clearance and secondary fuel tank used.
As shown the aluminum mount is in the way a hair can be filed some to fit and requires a thick O ring to seal the bottom side of the muffler ring for snug a fit. The top fits just fine.
Looks good always wanted to see if this was possible.
Other notes the plastic tank is more robust than a .020 tank. although would rather use the additional black back plate with an internal tank.
-43.9g .030 with throttle and available muffler pressure
-39.3g .030 back plate no muffler
-29.4g .020 with throttle
-25.1g .020 no throttle -added muffler / pressure
Note if you try using the muffler with the .020 it will not work with a pee wee tank as is would need to be cut for clearance and secondary fuel tank used.
As shown the aluminum mount is in the way a hair can be filed some to fit and requires a thick O ring to seal the bottom side of the muffler ring for snug a fit. The top fits just fine.
Looks good always wanted to see if this was possible.
Other notes the plastic tank is more robust than a .020 tank. although would rather use the additional black back plate with an internal tank.
#196
Thread Starter
Tried without pressure today with the white pill tank - with pressure it loaded up about mid way into the run.
Used the Lil Stinker 4 x 2.5 prop ran on 25% nitro
Stock TD.020 with throttle sleeve- best duration with new tank at full throttle- 4min 12 secs.
Used the Lil Stinker 4 x 2.5 prop ran on 25% nitro
Stock TD.020 with throttle sleeve- best duration with new tank at full throttle- 4min 12 secs.
Last edited by Pond Skipper; 07-08-2014 at 01:42 AM.
#197
Thread Starter
Here is a new vid / finally started using a editing program to cut n snip clips with better resolution.
[video=youtube; Removed - made a HD 1080p on the next page
[video=youtube; Removed - made a HD 1080p on the next page
Last edited by Pond Skipper; 07-12-2014 at 05:32 PM.
#199
Thread Starter
Thank you CP!
The rpm reads:
17.2k just prior to launch
18.6k right out of the hand
20.3k best level pass
Makes good thrust for 46-50 mph typical pass no pressure feed solid feel tracks good climbs out with ease -frame can handle 80mph.
I look forward to trying the thinner blades of the APC 4.2x2 prop / keeping with the no pressure theme the extra rpm will be good on the ears and in theory I can run leaner for longer run times.
Thus far 3.43 mins. is the best time with the 4x2.5
The APC is not quite constant pitch if the tips are cut to 3.5 dia may act like a 3.5 x 2+ Will try that after I run the stock prop next.
APC makes a 1/2A 5.5 x 2.5 may snag a few to cut down. 3.75 x 2.5
The GM .030 can swing a 4.5 x 2 at 18k ish I hope to get 25k with a cut 3.3 x 3 MA prop.
The rpm reads:
17.2k just prior to launch
18.6k right out of the hand
20.3k best level pass
Makes good thrust for 46-50 mph typical pass no pressure feed solid feel tracks good climbs out with ease -frame can handle 80mph.
I look forward to trying the thinner blades of the APC 4.2x2 prop / keeping with the no pressure theme the extra rpm will be good on the ears and in theory I can run leaner for longer run times.
Thus far 3.43 mins. is the best time with the 4x2.5
The APC is not quite constant pitch if the tips are cut to 3.5 dia may act like a 3.5 x 2+ Will try that after I run the stock prop next.
APC makes a 1/2A 5.5 x 2.5 may snag a few to cut down. 3.75 x 2.5
The GM .030 can swing a 4.5 x 2 at 18k ish I hope to get 25k with a cut 3.3 x 3 MA prop.