4-stroke engine recommendation
07-22-2013, 05:54 AM
#1
Thread Starter
4-stroke engine recommendation
I am looking for a 4-stroke engine to power a small bipe. The complete airframe minus the engine weighs 42 oz.
Right now it has a Magnum .30 4-stroke, which weighs 10 oz and balances the plane just right. However, it is severely under powered. It can't pull it through a loop even
diving before entering the loop to pick up speed, and flies dangerously slow. I am not sure if this is a problem with the engine it came with (swings a 9x6 at about 10,800 rpm oon 10% nitro), or this type of engine
is not the right one..
I think I would like to get about 45 oz of thrust (90% thrust to weight ratio).
Is there a 4-stroke engine in the 10 oz range that can deliver 45 oz of thrust with props in the range 9' to 10'?
Thank you
Alberto
Right now it has a Magnum .30 4-stroke, which weighs 10 oz and balances the plane just right. However, it is severely under powered. It can't pull it through a loop even
diving before entering the loop to pick up speed, and flies dangerously slow. I am not sure if this is a problem with the engine it came with (swings a 9x6 at about 10,800 rpm oon 10% nitro), or this type of engine
is not the right one..
I think I would like to get about 45 oz of thrust (90% thrust to weight ratio).
Is there a 4-stroke engine in the 10 oz range that can deliver 45 oz of thrust with props in the range 9' to 10'?
Thank you
Alberto
07-22-2013, 06:25 AM
#4
RE: 4-stroke engine recommendation
Well the Magnum .30 pulls my Global T6 around fast enough, no problem with loops, but I think it weighs much less than 42 ounces. Not a very good engine though, trounbles with the carb and valves sticking.
07-22-2013, 06:51 AM
#5
Senior Member
RE: 4-stroke engine recommendation
A biplane is going to have a lot of drag also. That would handicap enough speed entering the loop as well as slowing it more on the climb.
That being said, unless it is an "aerobatic" scale biplane, having to gain speed in a dive to do a loop might be pretty much a "scale" flight characteristic.
A Saito FA40 would only weigh a little less than 1 oz more than the Magnum 30, but it's currently "out of stock" @ Horizon. Maybe e-bay?
That being said, unless it is an "aerobatic" scale biplane, having to gain speed in a dive to do a loop might be pretty much a "scale" flight characteristic.
A Saito FA40 would only weigh a little less than 1 oz more than the Magnum 30, but it's currently "out of stock" @ Horizon. Maybe e-bay?
07-22-2013, 07:20 AM
#6
RE: 4-stroke engine recommendation
I would suggest the Saito FA-40A engine as it is a bored out .30 that now is a .40 and it develops a lot of power for its size. That ought to do the trick and it ought to more or less be a drop in replacement too.
07-22-2013, 07:21 AM
#7
Thread Starter
RE: 4-stroke engine recommendation
Bogbeagle is right. With a little wind it is very twichy. The Saito .40 looks good. I will keep and eye out. Thanks
Alberto
Alberto
07-23-2013, 06:39 AM
#10
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RE: 4-stroke engine recommendation
I had two magnum 30 four strokes on a Twinstar and they were dogs, bad power and idle. Put two cheap OS 25 LA on it and it was much better and flew great. Although i have not tested the "newer" Saito 40's, the older ones were no powerhouses, nor was the original OS 40 FS. I'm sure the newer model is great and has same mount as the 30. I did run a "newer" OS 40 FS Surpass and the power was very impressive.
07-23-2013, 06:46 AM
#11
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RE: 4-stroke engine recommendation
ORIGINAL: ululi1970
I am looking for a 4-stroke engine to power a small bipe. The complete airframe minus the engine weighs 42 oz.
Right now it has a Magnum .30 4-stroke, which weighs 10 oz and balances the plane just right. However, it is severely under powered. It can't pull it through a loop even
diving before entering the loop to pick up speed, and flies dangerously slow. I am not sure if this is a problem with the engine it came with (swings a 9x6 at about 10,800 rpm oon 10% nitro), or this type of engine
is not the right one..
I think I would like to get about 45 oz of thrust (90% thrust to weight ratio).
Is there a 4-stroke engine in the 10 oz range that can deliver 45 oz of thrust with props in the range 9' to 10'?
Thank you
Alberto
I am looking for a 4-stroke engine to power a small bipe. The complete airframe minus the engine weighs 42 oz.
Right now it has a Magnum .30 4-stroke, which weighs 10 oz and balances the plane just right. However, it is severely under powered. It can't pull it through a loop even
diving before entering the loop to pick up speed, and flies dangerously slow. I am not sure if this is a problem with the engine it came with (swings a 9x6 at about 10,800 rpm oon 10% nitro), or this type of engine
is not the right one..
I think I would like to get about 45 oz of thrust (90% thrust to weight ratio).
Is there a 4-stroke engine in the 10 oz range that can deliver 45 oz of thrust with props in the range 9' to 10'?
Thank you
Alberto
CR
07-23-2013, 08:05 AM
#13
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RE: 4-stroke engine recommendation
Do any of you blokes know how to calculate the amount of power produced by this engine ... 10,800 rpm on a 9 x 6 ?
Obviously, you can only estimate; but it would be interesting to have a figure.
Obviously, you can only estimate; but it would be interesting to have a figure.
07-23-2013, 11:26 AM
#14
RE: 4-stroke engine recommendation
The O.S. FS30 is rated at 0.5hp. The Saito 30 must be similar. Surpass 40 is 0.65 hp. All of these are rated at rpm's that would only be reached on fairly small props; not what you would normally use on a draggy biplane.
07-23-2013, 11:48 AM
#15
RE: 4-stroke engine recommendation
Alberto, when you say 42 oz without the engine, do you mean with fuel tank, prop, motor mount etc.? So the total weight is about 51-52 oz?
How big is this biplane...span, wing area? Seems like it shouldn't be quite so bad as you describe. Have you tried a 10x4 prop on it? The 9x6 might be inefficient if there is much drag.
I agree about getting a Saito 40a. Otherwise maybe an OS 30 FS. I guess you've ruled out a two-stroke.
Jim
How big is this biplane...span, wing area? Seems like it shouldn't be quite so bad as you describe. Have you tried a 10x4 prop on it? The 9x6 might be inefficient if there is much drag.
I agree about getting a Saito 40a. Otherwise maybe an OS 30 FS. I guess you've ruled out a two-stroke.
Jim
07-23-2013, 12:15 PM
#18
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RE: 4-stroke engine recommendation
It used to power an LT 25 with a nose gear and bolt on wing. I used two different props, if the grass was a little long I used a Graupne 10.5x5, if short grass a Graupner 10x5.5. When using the 10.5x5 the little LT would literally jump off the grass.
07-23-2013, 12:46 PM
#19
Senior Member
RE: 4-stroke engine recommendation
ORIGINAL: bogbeagle
Well, that's quite a bit of power.
I just don't understand how that is insufficient for the task of flying a 3lb bipe.
Well, that's quite a bit of power.
I just don't understand how that is insufficient for the task of flying a 3lb bipe.
The OP was refering to a Magnum 30, not a Saito.
07-23-2013, 02:09 PM
#21
RE: 4-stroke engine recommendation
My only experience with Magnum 4-strokes is a 52RFS. It was a dog until you put extra nitro in the fuel. It required about 2 gallons through it to finally wake up, and 20% nitro.
07-24-2013, 06:45 AM
#24
RE: 4-stroke engine recommendation
I put two of the newer Saito FA-40A engines in my P86 Twin plane. The plane can take off in maybe ten feet with a pylon race start. I only need 1/2 throttle to fly around well with the plane in the air too. The new Saito .40A engine is the size of the .30 engine it replaced and the Saito engine actually weighs a little less than a Thunder Tigre Pro .36 two stroke engine too. The engines have been running great too. I am using 11x7 props on the engines at this time.
07-24-2013, 07:16 AM
#25
Thread Starter
RE: 4-stroke engine recommendation
To clarify a few points:
1) the dry AUW of the bipe is 52 oz.
2) I have a Magnum .30 which does not seem to put more than .3hp with props in the 9x6 10x6 range. The exhaust valve is leaking. I tried to clean it, using toothpaste to gently lap it, but not too much luck.
3) I can try a Norvel .25 two-stroke, just to see how it flies. The weight is just about the same.
4) I'd still like to fly it with a 4-stroke. Been looking around for a Saito FA-40A, but so far no luck.
Alberto
1) the dry AUW of the bipe is 52 oz.
2) I have a Magnum .30 which does not seem to put more than .3hp with props in the 9x6 10x6 range. The exhaust valve is leaking. I tried to clean it, using toothpaste to gently lap it, but not too much luck.
3) I can try a Norvel .25 two-stroke, just to see how it flies. The weight is just about the same.
4) I'd still like to fly it with a 4-stroke. Been looking around for a Saito FA-40A, but so far no luck.
Alberto
