acdii

Just because of OF

https://www.youtube.com/watch?v=pAgnJDJN4VA

acdii

Which one are you referring to?

SrTelemaster150

The FA-115 is 36 gr lighter than the FA-125
It has the same size bore & valves as the FA-125 with a slightly shorter stroke thus it has better volumetric efficiency. Any difference in power output would be negligible)
The FA-115 fits into the same mounts as a .60 2-stroke/FA-65 (FA-125 is 6 mm taller, 4mm longer & 2 mm wider bolt spacing) The FA-100 is 7 mm taller than the FA-115, which begs the question, why would anyone opt for the FA-100?!
The FA-115 has 12 mm exhaust threads thus it has a much wider selection of exhaust options. (Why would Horizon list the odd exhaust thread as an advantage?)

And, the FA-115 costs slightly less than the FA-125..

SrTelemaster150

Good low friction wheels would be a MUST so that gravity induced drag doesn't skew the results.

Mount the engine on a skateboard with a tether for safety. A "die stay clamp" would secure the skateboard for starting purposes.

I have a digital fish scale & die stay clamps already. Have to look for a cheap skate board now.

acdii

Why? Because they were available at the swap meet for a good price. Paid about $180 or so for each one. One of the 100's needs bearings though, so that one wasn't such a good deal. The 125 was pretty barely broken in, had two flights and a crash which busted the end off the muffler. However, if I do need another 1.20 size engine, I will certainly look for a 115, they are on backorder at HH.

acdii

I have some drawer glides that are super smooth, you can pull the drawer in or out with a pinky. Those are what I was thinking of using.

blw

My Feedback: (3)

[QUOTE=Old Fart;12254107]I can feel a 125 joke coming...SO! acdc that was you prowling out the back of my shed after i threw my 125 out the rear window.Barry it never made the right 'loping' sound for me pard

I was talking about a 56, I think. Not the 125. My 125 is a good engine. Not the best engine in the Saito line, but an outstanding engine in it's own right.

blw

My Feedback: (3)

I've got to stick with the APC 15x6 for my 125. There's some 125's that love the 15" APCs over the 16" props for whatever reason and whether it makes sense to you or not. Mine is one of those. I haven't wasted time slapping on any MA props as they always fail miserably to put out the power and grunt the APCs give you. W8YE and I have talked a lot about the 15" engines vs the 16" 125's. No idea why it happens. Mine is one of the first batch sent to Horizon. I will say that engine was a bit tough to keep tuned dead on for a while. The sweet spot wandered for a few gallons.

Yep, 40 minutes will get you in the air just fine and you should be flying once you get that on the engine.

Hobbsy

My Feedback: (102)

I started a spread sheet for engine rpm listing max rpm, fuel % and idle. To be fair I unboxed the OS 1.20 Surpass it did as follows

OS 1.20 S
Prop=====MA Classic 16x6
Plug=====OS-f
Fuel=====Wildcat 10% full synthetic
Exhaust==Stock, very loud muffler
Max rpm=9,250
Idle=====2,000, I could not get below 2,000 no matter what I tried.,

Back to a Saito.
Saito FA .40a well used with new Boca Bearings
Plug====Fox Miracle
Prop Xoar 11x6 at w8ye's suggestion
Fuel====Wildcat 10% full synthetic
Max rpm=9,750
Idle 2,050

SrTelemaster150

That should work.

Rudolph Hart

Good news mate..don't forget to put the 125 in the draw first before you close it.Just kidding and thanks for the acdc vid

Hobbsy

My Feedback: (102)

The 1.25.


The power difference is not negligible the 1.15 turns a 15x6 @ 8,800, the 1.25 turns a 16x6 at 9,000. YS owners would say that power difference is one engine stomping the other. Below is my re-built 1.00 turning a Xoar 15x6.

Fuel Wildcat 10%/18% full synthetic
Plug===Fox Miracle and old well used one
Prop===Xoar 15x6 for all the above
Max rpm-8,900 rpm
Idle==1,835

SrTelemaster150

Unless the tests were performed with the same make/brand propeller, the same fuel, on the same day, at the same location & under the same atmospheric conditions, they don't mean diddly squat.

Now you want me to believe that the FA-100 will out perform the FA-115 by 100 RPM?

The FA-125 I tested barely out performed my FA-91 when both were running with CDI & 15% Kool Power. FA-91 9700 RPM, FA-125 10,000 RPM, both with 15 x 5 Zinger.

But then again it wasn't the same day or atmospheric conditions so it holds about as much water as the numbers you cited..

As soon as I get my home renovations done I'll see what the FA-115 will do with both GI & CDI.

BTW, the FA-125 wouldn't pull a 16 x 8 W/O detonating & throwing the prop after a few minutes @ WOT. Something I have never seen with any Saito engine when running with CDI.

I'd be willing to bet an FA-120S would pull a 16 x 6 all day @ WOT W/O doing that.

Along W/the tuning issues that were present at midrange, I was not impressed at all.

Hobbsy

My Feedback: (102)

Dan, I simply typed out the numbers I got when it was 100 degrees F. I stated Horizons numbers and then mine, I did not start a war of words, I just recorded what happened. Nobody will buy that a .91 is more powerful than the 1.25 when it's not even more powerful than the 1.00.

blw

My Feedback: (3)

You have to keep in mind these are just static tests and don't mean anything regarding how the engine will fly. You can look at it as the engine flying the prop or the engine & prop flying the airplane.

I don't particularly like math at all, but the formula to test prop efficiency tells us a lot about what is going on if you read how the formula works. The formula shows that it's a no brainer that larger props pull better because of the larger radius of air velocity and volume going through the prop. You add that to the speed the prop/engine/airplane is flying, so you have two velocities to work with- v and V. That larger radius means a lot to the bottom line of performance. Static tests only give you one of the necessary velocities.

I don't put much into static engine tests except to listen to the engine itself, and to see if all sounds like it did the last time checked. The real test is in the air.

SrTelemaster150

Read my post again. I didn't say that the FA-91 was MORE powerful than the FA-125, I only posted that it only made 300 more RPM than the FA-91 with the same prop. And, I was careful to qualify my number with the disclaimer that the tests were done at different times under different conditions..

You on the other hand post numbers that suggest that the FA-100 IS more powerful than the FA-115 with no disclaimer & nobody is going to buy that.

Hobbsy

My Feedback: (102)

I posted the numbers the 1.00 made I don't remember the numbers my 1.15 made, I wasn't all that impressed by the 1.15 and I sold it. That's it. I like it better when discussing engines is fun.

acdii

I do know that the Fa-125 can run backwards very well. Mine started backwards and I had no way to shut it off, and it kept running, smoothly, even as I advanced the throttle. I finally just pushed the starterinto the cone and pop, it ran the correct direction. The guy holding my plane said he has never seen any engine run that good backwards.

OF, if you hate that 125 so much, go dig it out of the backyard and send it to me, I will find a nice home for it.

acdii

I did have my 100 GK in the Mustang the 125 is in now, and it flew it well. Too bad I dont have baselines on performance between the two in the same airframe, but I might just do that since I can easily swap them out for the other with no mods other than throttle adjustment. If I can find someone with a radar gun I can do several high speed passes with each, that should help.

Hobbsy

My Feedback: (102)

Be careful AC. Pete may have fed the 1.25 the wrong kind of alky.

acdii

Well if he fed it scotch, that WOULD explain why he had to toss it. Have to use Bourbon if you want it to run right.

SrTelemaster150

Any time someone disagrees with you, you jump to conclusions, misunderstand the text & you seem to get offended. That's why you don't have "fun".

Hobbsy

My Feedback: (102)

Good One AC, I am going to take Barry's and C 429's hints and put another 60 minutes on the 1.25 at near peak and see where we end up. I have a 16x6 Xoar coming today and I broke down and ordered an APC 16x6 to do a test. No one seemed to notice that I ran my ancient OS 1.20 Surpass, (with new Bowman ring and Boca Bearings), with the same MA Classic 16x6 and it out turned the Saito 1.25 by about 225 rpm. Engines is funner than anything.

SrTelemaster150

I always run engines that I am comparing on the same day and/or run an engine that has already established a baseline for "control". When that is done, static testing is a useful tool to compare performance.

Static testing is a useful tool to estimate what propeller will be suitable for a given airframe.

Static testing will give an indication as to how the plane will perform during takeoff or in vertical as the plane scrubs off momentum. The rule of thumb is that 1 1/2 times the weight of the aircraft in static thrust will achieve unlimited vertical.

Given that rule, a = or >24# of static thrust should have unlimited vertical with a = or <16# aircraft.

As cited, different aircraft will react differently in the air. A sleek aircraft like a P-51 should never be propped at or near maximum RPM static as the prop will unload in the air & RPM will increase as speed increases.

Something like a J-3 Cub can be propped static to within a few hundred RPM of maximum due to the fact that the aerodynamic drag will prevent high speeds that would allow RPM to increase significantly.

BJ64

Just my 2 cents worth on "drawer guide" thrust measuring tools....

I opted for some really nice multi-ball drawer sliders. My test were 20 to 40% less than what others had quoted using different methods.

So I tried pushing down on reliable electronic scales, and sure enough, my readings for the same combo were suddenly 20 to 40% higher. Mind you, these were done using electric. Back to back using the same motor, prop, ESC and battery on both test rigs.

The important part here was that it illustrated to me was that even if you can't "feel" any perceptible drag on your horizontal rig, there maybe more drag there than you realise, and your static figures may be quite a bit less that 'absolute'.

I then opted for some 'linear' bearings - but haven't gotten around to building a new test rig to use them yet. If I ever do, I'll run back to back to back tests to see what sort of correlation I get.

And yes - while what you get during a bench test can vary a fair bit to what you get during actual flight, at least is can serve as some sort of a guide. Apples to apples kinda thing. i.e. if something is pulling 1/2 a kilo more thrust just by switching from, say, a 7x5 prop to an 8x6, it's pretty easy to see which one produces more thrust. But...at what cost? In electrics, you can pretty easily see which one draw more Amps and induces more battery sag over time.

I/C engines seem to work the opposite way - over-prop them and they'll just slow die in rpm and either stall the engine.. or stall the aircraft.

With electrics, the more you ask of them, they more they will try to deliver. The ESC/battery/motor will keep on trying to to give - until something burns out. Usually the weakest link in the chain. Be it the motor, the ESC, or the battery.

All the above guff said - *any* test bench can still provide a level of comparison between changing one thing in an engine/prop/(fuel) combo, providing only one thing is changed at a time, and the test bench and environmental conditions remain basically the same throughout each testing process.

How absolutely 'correct' that measurement is does have a bit to do with any friction of all the measuring components involved doing a kg/lb pull/push test.

When testing anything v's anything else, I try to keep things as fair and constant as possible. i.e. change only one item, and don't test today when it's 15 deg C and humidity is 80%...then run the other test tomorrow when it's 30 deg C in the shade with 60% humidity.

It's all E=MC^2 in the end...

BJ