Gas radial engines
#501
Thanks Hector I don't know I hadn't considered this effect. The carb is quite exposed in the cowl. I do heve close baffles around each cylinder and luvers behind each of the cylinders. What would the solution be to reduce this effect?
#502
The idea is for the carb to breathe within a plenum where pressure differences are not really that pronounced; this means a volume with dimensions much larger than the trumpet's bore and as much separated as possible from openings that create negative pressures (louvres) @ speed. Ideally, then, the carb should breathe through the fuz - which, in turn, should have some air pressure "relief" holes (i.e. openings parallel to the flow direction, ideally at the bottom and/or sides) to maintain an even atmospheric pressure at any speed.
What I did in practice: my FG-60carb was just 1cm from the face of the firewall, a distance dictated by the length of the stand offs I used (had to be longer than Saito's). This would give rise to uneven flow, since the ~1cm distance is comparable to the trumpet's diameter plus it would only breath through the cowl's volume the pressure in which is strognly affected by speed (I also got louvres). So, I opened up a hole (28mm) in the firewall right opposite and then used a sort of "sleeve" to take up the distance, so that the trumpet could breathe "cleaner" air from within the fuz plenum. As it happened, I had measured several plastic cups from... toiletries' bottles until I found a plastic dosing cap from a medicine bottle to be a perfect fit. Photos below tell the story..
What I did in practice: my FG-60carb was just 1cm from the face of the firewall, a distance dictated by the length of the stand offs I used (had to be longer than Saito's). This would give rise to uneven flow, since the ~1cm distance is comparable to the trumpet's diameter plus it would only breath through the cowl's volume the pressure in which is strognly affected by speed (I also got louvres). So, I opened up a hole (28mm) in the firewall right opposite and then used a sort of "sleeve" to take up the distance, so that the trumpet could breathe "cleaner" air from within the fuz plenum. As it happened, I had measured several plastic cups from... toiletries' bottles until I found a plastic dosing cap from a medicine bottle to be a perfect fit. Photos below tell the story..
Last edited by hpergm; 04-15-2015 at 10:03 PM.
#503
Thanks Hector, it all makes sence, have you flown it yet with these modifications, I think I have a bit of work to do to try and seperate the carb intake from the cowl and create a fuz plemum. See pictures below, but all possibule I think, i like the idea of the plastc dosing cap, I'll copy that idea.
Also looking at the Saito instructions it does have the carb inside the fuz.
Also looking at the Saito instructions it does have the carb inside the fuz.
#505
John, your installation does not look too bad actually.
Mine is on a scale FW190 (Top Flite), where the cowl plenum happens to be completely isolated from the fuz volume. That's why it made sense for me to do it this way. And no, I do not use the pressure tap.. Too scared, due to flammability.
Now, your Yak is completely different, very open and will not have this problem as pronounced. I would initially try to open up a couple of holes in the Monokote between the side trusses (e.g. right aft/below the wing, where it does not show) to make sure the fuz breathes/balances with atmospheric air. I will try to post a pic of what I did to my Yak for this exact same reason.
Another easy trial would be to partially restrict your louvres (towards the rear - closer to the carb) - while watching how temps behave. This will reduce the vacuum effect @ speed. Finally, you could try to just remove the positive pressure from the Keleo to the tank, retune and fly. See what happens then...
Mine is on a scale FW190 (Top Flite), where the cowl plenum happens to be completely isolated from the fuz volume. That's why it made sense for me to do it this way. And no, I do not use the pressure tap.. Too scared, due to flammability.
Now, your Yak is completely different, very open and will not have this problem as pronounced. I would initially try to open up a couple of holes in the Monokote between the side trusses (e.g. right aft/below the wing, where it does not show) to make sure the fuz breathes/balances with atmospheric air. I will try to post a pic of what I did to my Yak for this exact same reason.
Another easy trial would be to partially restrict your louvres (towards the rear - closer to the carb) - while watching how temps behave. This will reduce the vacuum effect @ speed. Finally, you could try to just remove the positive pressure from the Keleo to the tank, retune and fly. See what happens then...
Last edited by hpergm; 04-16-2015 at 07:13 AM.
#506
Thanks Hector, yes please post pics of your Yak set up. I'll try removing the positive pressure first as this is the easiest to do then if no difference restrict the louvers near the carb and see how I get on.
#508
Hi Hector and all, I had 3 flights last night with out the positive pressure feed from the tank and the engine is performing much better much better............. so advice to anyone using the Keleo ring is there is no need to use pressure fed to the tank.
#510
Also posted over in the FG-60R3 forum - first flight session with the engine...
https://www.youtube.com/watch?v=x_MYY0NlbQY Prop is an APC 22x10 with a top end of 6,800. Mix was 1:20, using Castrol Synthetic. The engine tuned easily (6.5 turns out on the low and ~2.5 turns out on the High) and Ran like clockwork.
The on-board telemetry sensors for temps (1 per cylinder) showed only a deviation of <2degrees C on the ground (idle) and in flight for (mid-range)..! Seems like the careful running-in (see previous posts) paid dividents.. Temp range was between 80-90C on the ground.
Note: readings are taken between the fins just below the spark plug, on the rear side (to avoid speed/cooling effect of oncoming airflow). In reality, CHTs will be 30-40C higher on near the top of the combustion chamber.
A +20C difference between Nos 2&3 and No.1 (top cylinder) was recorder after prolonged mid/high throttle settings in the air. This was expected due to the relief airflow arrangement in the cowl (louvres only on the bottom side for scale reasons suck more cooling air around the bottom cylinders...).
A Happy customer!
https://www.youtube.com/watch?v=x_MYY0NlbQY Prop is an APC 22x10 with a top end of 6,800. Mix was 1:20, using Castrol Synthetic. The engine tuned easily (6.5 turns out on the low and ~2.5 turns out on the High) and Ran like clockwork.
The on-board telemetry sensors for temps (1 per cylinder) showed only a deviation of <2degrees C on the ground (idle) and in flight for (mid-range)..! Seems like the careful running-in (see previous posts) paid dividents.. Temp range was between 80-90C on the ground.
Note: readings are taken between the fins just below the spark plug, on the rear side (to avoid speed/cooling effect of oncoming airflow). In reality, CHTs will be 30-40C higher on near the top of the combustion chamber.
A +20C difference between Nos 2&3 and No.1 (top cylinder) was recorder after prolonged mid/high throttle settings in the air. This was expected due to the relief airflow arrangement in the cowl (louvres only on the bottom side for scale reasons suck more cooling air around the bottom cylinders...).
A Happy customer!
#511
Hi guys, my P-47 with FG-60 R3 is already in flight, today I did the maiden flight with Graupner G-sonic pro 22x10 propeller, 7000 rpm full of power, great prop.
https://www.youtube.com/watch?v=XL-cCVzCw4w&feature=youtu.be
https://www.youtube.com/watch?v=XL-cCVzCw4w&feature=youtu.be
Last edited by Alex70; 05-24-2015 at 09:32 AM.
#512
#513
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Its an private video Alex.
#517
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Hey guys, I finally got my hands on a Saito FG60 R3 to check out the inlet manifold.
Here are the pics from a brand new one a friend bought, he wanted to know if Saito had made suitable changes.
So there you have it, a bronze bush and entirely redesigned inlet manifold for an engine that officially has no issues....
Here are the pics from a brand new one a friend bought, he wanted to know if Saito had made suitable changes.
So there you have it, a bronze bush and entirely redesigned inlet manifold for an engine that officially has no issues....
#518
Thanks for the pictures Blair, looks good.
Just had flight number 30 on my stock 84FG last weekend, and its running great.
It is still breaking in, and I have not touched the needles since initial ground run break in.
Had one engine out during a landing approach because it is running rich, and the idle speed had dropped because of it being a little more broken in :-)
I like it rich, so I just bumped up the idel speed on my tx.
Would like to make an exhaust ring to bring out the sound a little more...the stock flex pipes are a little tame...... :-)
Video from a few weeks back......
https://www.youtube.com/watch?v=jhXmktYohnM
Just had flight number 30 on my stock 84FG last weekend, and its running great.
It is still breaking in, and I have not touched the needles since initial ground run break in.
Had one engine out during a landing approach because it is running rich, and the idle speed had dropped because of it being a little more broken in :-)
I like it rich, so I just bumped up the idel speed on my tx.
Would like to make an exhaust ring to bring out the sound a little more...the stock flex pipes are a little tame...... :-)
Video from a few weeks back......
https://www.youtube.com/watch?v=jhXmktYohnM
#519
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Tidy unit mate, definitely go ring exhaust, those flex pipes steal every bit of authenticity from a radial.
Last edited by Blair K.; 08-30-2015 at 04:19 AM.
#520
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Hi There,
I've just finished breaking in my FG60R3. Went perfectly. Never had to touch the low end mixture. Throttle response is smooth and instantaneous.
One question: I found I had to choke the carb with my finger to get it started. Necessary to pull the fuel up from the tank, which is a bit below the carb, unfortunately. Has anyone else had this experience? I'd like to avoid putting a choke mechanism in the bowels of the plane, and moving the tank higher is difficult in my model (a scratch built 1/5 scale Mr. Mulligan)
Thanks!
I've just finished breaking in my FG60R3. Went perfectly. Never had to touch the low end mixture. Throttle response is smooth and instantaneous.
One question: I found I had to choke the carb with my finger to get it started. Necessary to pull the fuel up from the tank, which is a bit below the carb, unfortunately. Has anyone else had this experience? I'd like to avoid putting a choke mechanism in the bowels of the plane, and moving the tank higher is difficult in my model (a scratch built 1/5 scale Mr. Mulligan)
Thanks!
#521
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Hi There,
I've just finished breaking in my FG60R3. Went perfectly. Never had to touch the low end mixture. Throttle response is smooth and instantaneous.
One question: I found I had to choke the carb with my finger to get it started. Necessary to pull the fuel up from the tank, which is a bit below the carb, unfortunately. Has anyone else had this experience? I'd like to avoid putting a choke mechanism in the bowels of the plane, and moving the tank higher is difficult in my model (a scratch built 1/5 scale Mr. Mulligan)
Thanks!
I've just finished breaking in my FG60R3. Went perfectly. Never had to touch the low end mixture. Throttle response is smooth and instantaneous.
One question: I found I had to choke the carb with my finger to get it started. Necessary to pull the fuel up from the tank, which is a bit below the carb, unfortunately. Has anyone else had this experience? I'd like to avoid putting a choke mechanism in the bowels of the plane, and moving the tank higher is difficult in my model (a scratch built 1/5 scale Mr. Mulligan)
Thanks!
I would first ask how far below the carby the tank is??
My experience with Saito FG radials is they don't have a very strong fuel pump. Dont assume they pump fuel like a 2 stroke with a walbro style carby , its a much weaker pumping system.
If the engine has ran before there will oil on internal surfaces so id suggest using an electric starter, i found it pumps up in 2-3 seconds and protects fingers too!
Cheers BK
#522
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I had similar experiences running and breaking in this engine. It was a breeze, one of the nicest engines I have ever run in. Nice smooth idle, good transition. I installed a Keleo collector ring exhaust on mine too, what a great deep Harley sound at idle! My fuel tank is centered with the carb, and when I hand flip the prop, I immediately see gas flowing through the line to engine. If your fuel tank is lower than the carb, you might try holding the tail up level whilst turning over the propellor to prime( ignition off) This brings the fuel supply more level with carb, and once wet, it should start.
#523
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Thanks Blair and Pete,
With to your expert answers, I'm confidently in the process of moving the location of the tank in the plane. Can't wait to fly it, but I'll post pictures before I do.
With to your expert answers, I'm confidently in the process of moving the location of the tank in the plane. Can't wait to fly it, but I'll post pictures before I do.
#525
Senior Member
Hey guys, I finally got my hands on a Saito FG60 R3 to check out the inlet manifold.
Here are the pics from a brand new one a friend bought, he wanted to know if Saito had made suitable changes.
So there you have it, a bronze bush and entirely redesigned inlet manifold for an engine that officially has no issues....
Here are the pics from a brand new one a friend bought, he wanted to know if Saito had made suitable changes.
So there you have it, a bronze bush and entirely redesigned inlet manifold for an engine that officially has no issues....