Engine Selection
 

Got everything I need to get back into flying and I am going to build an LST . I have the following engines; TT-.07 purple head, Cox Black Widow , AP-.061. All are new in the box and I was just wondering which one you guys thought would be most suited for the LST. I also need some servos and was thinking about HS-81 Hi-tec servos. Any thoughts.

I'm thinking for that plane the HS-81's might be too heavy and you don't need that much torque. You'd do yourself a favor picking much lighter servos. I would choose the TT with a close second with the AP, then the Black Widow. Just my opinion.

What servos would you buy. I wasn't sure how much torque I needed.

I have no idea what a LST is. I need specs on this plane. The Cox has it's own tank. Turns the highest RPM, has the most expensive glow plug, and fuel requirement. Lots to consider. Do ASP .061 run OK? A popular saying is there is no replacement for displacement, all other things being equal.

I'm not an expert at this scale, but several years ago I was researching for a postal plane called the "Grace". It was designed with the Cox .049 engine in mind to keep costs down as well as using an easy to run engine. People who built copies found that it was a better plane when built lighter. Meaning, some models built were not the lightest and suffered in their flying ability. Since the conception of the design, smaller, lighter servos and batteries have become plentiful, and at pretty good prices. So, with that in mind, I'd recommend servos in the "sub-micro" range, like a HS-55. 8g/ 16.66 oz-in. I don't think I'd go Nano, unless you use one for the throttle. The "Grace" was designed right at the cusp of some of this lighter technology. Again, remember these suggestions are my opinion, and I would hope others more experienced at this scale would chime in.

HS-65HB are a good strong micro for 1/2A's. HS-55's have an notiously light gear train, they are the only micro I've stripped by bumping a park flier rudder on something. That said, they do have enough power for most 1/2A applications.

Most of the threads on the engine point out that the TT .07 is an exception to that rule about displacement. Runs fine but no powerhouse. In this case adding displacement counteracts the unequal level of performance and you get a mild mannered throttled engine with decent but unexceptional 1/2A level power.

If the AP .061 runs and behaves well enough that you are comfortable using it, you'll have a throttled 1/2A but again offering no more performance than the Cox.

The Cox has simplicity and nostalgic appeal going for it. Fuel, prime, flip and go.. fly 'till it runs out, can be all kinds of fun.

Cost of fuel for a 1/2A is not much of an issue.

If servo weight is an issue in whatever this LST is (wing type, wing span?) go with the Cox, one less servo, http://www.ebay.com/itm/24-Nitro-Glo...3D222349453233

J330 the LST Trainer is a sticky at the top of this forum this forum page. There are plans and a complete build . Looks like a 1/2a sig kadet to me.

I have been buying engines over the years as I found them and my reason for the post was I figured because these are common some of you had tried one. I bought two of the TT engines cause I thought they were pretty . I found a new OS FP 15 about 2 years ago. I would love to pick up a goldberg eaglet kit for it.

Please recommend any brand of servo you think is appropriate. I have a new Spectrum Radio 6 chanel.
I'm just not sure what size/torque on these small planes.

The TT .07 with the right prop can. I recomend the HQ Carbon blend props for performance.
I would also consider using the APC 6x4 thin blade and low weight for thrust.


https://www.youtube.com/watch?v=P10X...ature=youtu.be

https://www.youtube.com/watch?v=P10XsPvkleM&feature=youtu.be Uploaded on Dec 18, 2016

TT GP .07 cu. in. / 1.15cc
ABN engine / spec 3,500 to 24,000 rpm 95g stock weight.

HQ 5x4.5 30% nitro / 20% castor
Ran in about 2oz of fuel prior to test. 4 heat cycle break in / rich.
Static 19,864 / 12.1oz thrust / 74 mph / 118w / .158hp

Engine is quite with stock muffler and runs very clean with
it's integrated carb. NV holds settings, no air leaks. Idle
having a air bleed works very well. Transitions are fine.
Should hold 20k after some more running in. Compression
is good, needs 1 more thrust washer or one thicker the gap
is a bit much for my taste. I tried a MA 5.5x4.5 was not
spooling up as well being 5.5in dia but also due to the extra
weight and thicker airfoil. If you prefer robust props I recommend
also the MA 5x4.5.

Does not come with a muffler gasket, a online vendor makes
them. Fuel line is two sizes and long not for best flight performance
but good enough for static running. Easy start with med temp plug.
Engine is perfect for planes requiring a clean running engine, no drips,
all the spent oil went out the muffler. Clean at the prop thrust plate, nothing
around the top or carb. O ring for the NV is a bit tight, I had it oiled and
it was still tight to turn.

Gasket vendor makes many types:
http://www.ebay.com/itm/320885791416...%3AMEBIDX%3AIT

Geez, I find that actually impressive . Thanks for sharing that Pond Skipper.

Just thinking. Even a Cox .049 Flyer, which has a throttle might even be considered. A Black Widow could be converted to have a throttle. See my engine test runs with different heads. https://www.youtube.com/watch?v=pdnC55uOhfk

I would never run Hitec HS55 or any HS-80,81,82 or 85s with plastic gears... MJD is spot on for the servos. Those Hitec HS-65HB are the best small servos out there. very very strong gear train, light weight and no slop over time. Of those three engines I say the AP then TT then black widow. Run the APC 6x4 1/2A prop. it is a big load for it but pulls large planes very well and is about 19 ounces of thrust in a plane.

I've been having good luck with Dymond 4.7 servos in a couple of 1/2A planes the last few years. Small, light, strong, reliable(so far), but not the cheapest on the market. Been satisfied with them enough that I've bought some smaller 3.7s and larger 6.0s to use in slightly smaller and larger glow models in the near future. I've used lots of HS-55s in 1/2A planes over the years but have had to replace at least a handful of them. Never lost a plane due to a failure. They just got to the point that they started quivering at the neutral position. I always pulled them from service when I saw those symptoms. Still have some in service, bit my newer stuff is flying with HS-65MGs or Dymond servos. No failures so far.

I had a few quivering HS-55's, and the one I totally stripped by bouncing the rudder on the ground in the pits. Great on electric parkies, but I would avoid them with glow.

I've used the HS65's on up to .15 tail surfaces, I flog the crap out of them on electrics, and on several 1/2A's. I really like them. It was Combatpigg who first trumpeted their virtues on this forum, maybe 7-8 years ago, and I own more of them now than any other small servo.

The Dymond 6.0 and 4.7 are known to be pretty tough little servos. I have a couple of D60, great servos and I believe they would do the job great on 1/2A's, but I only have experience with two so far so that's only an opinion. I know I would have bought a handful of D60's had the HS65's not come along.

Tee Bee should try the HS-65HB servos lighter and much better than the metal gear ones.

11g, good for 6v (31 oz-in!) and tight, strong gear train. I have run a few of them on a 2cell LiFe pack but nobody recommends that. I think the resin gear train in the HS-81 is weak relative to its rating. It weighs about 50% more than the HS65HB, but has about 33% more torque. The 65 already has more torque than any 1/2A needs unless you make stiff linkages, which isn't the servo's fault.

I use these cheapo's in my 1/2A Lil Speedy thus far after many flights over 100mph no issues.

http://www.ebay.com/itm/1x-Micro-9g-...id=p5731.m3795

Just 9g as I recall bit more than that really with the wires.

• 1.6 kg / 56.4oz @ 6.0v

This ones are outstanding servos, more than enough for your project:


https://hobbyking.com/en_us/hobbykin...sec-13-5g.html

Support those who support you. by buying cheap servos we are hurting the hobby industry and those big names that made the hobby. By buying cheap soon all we will have is cheap....

Here is one to help with that warm and fuzzy feeling.

http://www.rcuniverse.com/forum/atta...mentid=2194500
http://www.ebay.com/itm/Savox-SV1232...YAAOSwvzRX1hxp

Savox SV1232MG Micro Digital Servo 0.05/69

US $99.99

Too bad he only has two of them....

http://www.ebay.com/itm/Savox-SV1232...sAAOSwyQtVrp3u

This guy has 8 of them $61.80 ea. so for a mere $494.40 your all set with 8 servos... not as greedy on profit / with free shipping.

That may be a good servo but one thing to think about with ANY high speed servo is amp draw. High speed servos constantly try to stay centered like all servos but with less torque being applied to the motor it draws more power. So on a small plane with a tiny battery you will need to watch the battery capacity. You can almost double the power drawn from the battery going from a .10 speed to a .05 speed servo.

Thus far with no issues:
I use 1S 80mah with my 1.7g / 2.2g servos - TD .010 / 130.4 mph
(engine moved to new plane for next level testing)

4cell 140mah with 2.7g / 3.7g servos TD .020 / 106 mph
(engine moved to new plane for next level testing)

4cell 270 mah with 4 to 7g servos TD .049 / 122 mph
(still prop testing room yet, will need a new plane soon)

4cell 400 mah with 9g servos TD .09 / 148 mph (done needs a new plane)

Next summer I will do more testing with the TD .01 / .020 and .049 I am done
with the .09 as it will require a new plane to go faster. .049 will need a new plane
after a few more tests. 4x5N will be it's best prop leaving enough thrust on the plate.

I like high torque over speed for servos and of course small cases
for planes up to .049 is a must. I don't like thirsty high end servos.
Will be putting a TD .15 on something new for next summer. Such broad
prop selection 170 mph is possible. 5.5 x 6.5 should yield a frightening blur
28k down wind. 14g -17g servos / 4cell 600mah range.

4 to 5 flights per session is enough for me.