Maxam

My Feedback: (62)

I just found out, the Saito 325 radial is now discontinued. Kinda sad. -Tom

ogg2000

Maybe this sound will bring some audible enjoyment...
This is the last run after several tanks of running in. Mixture still rich so a few more rpm to get. Propeller is APC 20x10, fuel is Model Technics Bekra 16 (heli fuel)

I love the sound at half throttle

Fitted to my ESM Sea Fury, but not flown yet, it will have to wait for next year.

<iframe width="560" height="315" src="https://www.youtube.com/embed/qHwEnQEv_qI" frameborder="0" allowfullscreen></iframe>

Maxam

My Feedback: (62)

Ah yes!!! Very nice. Thank you!

Rudolph Hart

The kelio ring exhaust makes them sound much better than the standard flexi tubes,thanks.

Fulcrum2111

Is a must to have a glow driver on board on radial glow engines like the evolution 7-35? Because of weight I want to run the glowplug harness and use a 1,2v 10Ah battery to start the engine and run without on board power. Will some cylinder drop in flight without the glow driver??

jymster

My Feedback: (9)

Hi Fulcrum,


An onboard glow is not a 100% must, but it does make life easier, especially for starting. Also gives a very reliable idle. In any case you should always tune the engine to get the best idle without onboard glow (OG), and the the OG just improves reliability further.


Also, no need to be concerned about the weight if you use a Microsens unit from Austria. They are super small and lightweight. Below are the single/twin cylinder and 4 cylinder versions, the 7cylinder unit is same size, but a little bit thicker. By the way, the Aussie 10 cent coin in the photo is a bit smaller than a US quarter.

Fulcrum2111

i see that the cables that go to the glow plugs have to use a cable connector. Where can I find it?

redball8

My Feedback: (128)

That Microsens unit looks like it's for a single cylinder. The real weight issue isn't the glow driver unit, but the battery to drive it. For seven cylinders and using the McDaniels unit figure an amp per cylinder, or seven amps, from a 4-cell pack. A battery in the 3300-4000 mah range makes sense, which will weigh ~260g (9 oz). Then figure another 240g (8 oz) for the onboard glow unit.

If you break them in right, the glow driver isn't essential. Maxam always ran his this way, and swears by it. But that means about a three-hour break-in, letting the engine cool down every five minutes or so. I break them in this way, note they run well w/o onboard glow, but opt for the peace of mind of onboard glow.

Fulcrum2111

For the microsens I have been looking for a lipo 3.7v 4000mah 8C that weighs 70gr. Also the plug leads should compensate for the weight of the glow plug harness.
In the past I used the cdi conversion For this engine 7-35 specially for break in but I have uninstalled it because it weighs almost 1kg including ignition sensor magnets spark plug and lipo battery. My airplane is a high wing but it is already too heavy to add such big extra weigths. But I fear that if i dont use the glow plug driver the engine could quit a cylinder and that would mean a crash because the plane needs every single hp from it to fly well.
about the ease to start I will be using an elecric starter because it is a cowled engine and priming for the fisrt time is not easy by hand as it does not have a pumped carb.

ya33a

Hi Fulcrun 2111,

I am in the process of installing the Saito R325 in a Sukhoi SU26, I intend to run the Microsens glow driver for peace of mind, I also needed to loose quite a bit of weight as the wing loading went through the roof, so opted to make the tail as light as possible and move the bulky items closer to the CG to get it to balance. Running a 3 blade prop 20x8 for ground clearance issues...

Maxam

My Feedback: (62)

Ya, the saito 325 is an especially reliable engine. It is not very powerful so light weight is important. No on glow needed. The prop you are suggesting is too big and not as efficient. Use a 20x10 two blade. Now the engines number one flaw is its carb. It is fine at idle and full throttle but the mid throttle is way too rich. If you can, order the OS 160/FF240/FF320 carb and you will need to make an adapter on the lathe. If you cannot do this , perhaps a friend? You would be absolutely thrilled with the difference in operation of the engine. On my yak 54 I had a 24 oz tank which was good for about ten minutes. Switching to the OS carb without fuel guzzling mid throttle I could fly 10 minutes on a 16 oz tank! The engine sounds way better too. -Tom

jymster

My Feedback: (9)

Hi redball,

Yes, those two units were for 1-2 and 4 cylinders, you are correct. However the 7 cylinder version is same width and length, but twice as thick (see below). The weight of the GLOW7LP is only 18g (0.63oz), which is a fraction of the McDaniels. It runs on a 1S LiPo pack or 3 cell NiMh (i.e. 3.6-3.7V). I've found these from Hobbyking to be the most convenient, which only weigh 168g: https://hobbyking.com/en_us/turnigy-...-approved.html . Fulcrum, what is the 4000mAh 8C pack you've found? That would be interesting.

redball8

My Feedback: (128)

Wow - those Microsens units do look good! I'll have to check them out ...

Fulcrum2111

Got the microsens unit, it is very light, I recommend using a one cell lipo 4000mah thats light and gives enough voltage.

chasrb

I wanted to see if anyone has done a gas conversion of their radial? I have the Siedel 7 cyl glow that I am looking to maybe convert to gas. I see where CH ignitions has a kit for the Evolution radials, I wonder if it would work on the Siedels. I also have a pair of Saitio 170R3 on a F7F I am also thinking of converting to gas.

Silver Lotus

I bought a Morris Mini Motors conversion kit for my Evo 999.
Haven't started it yet.
Expensive 'tho.

tdevince

Hello,
I am thinking about getting an OS FR7-420 but I can't find much operating experience with this engine. I realize the price will send a lot of people over to other brands. Most of my engines are OS and I really like their engines. The only multi cylinder I have is an OS Gemini 160 and love that engine. I like the OS quality built into the engines I've owned.

1. Does anyone have experience with the FR7-420?
2. Are there any issues I should be aware of with this particular engine?
3. I assume the power output will be comparable to the Evolution 7-77 (for purposes of determining if its a good match for a particular airframe)
4. What do you like/dislike about this engine?

Thank you,

Tom

Rv7garage

My Feedback: (10)

All I can say is that if I had that engine, I would probably never fly it - just mount it in a test stand and run it all day haha

What airframe(s) are you considering?

tdevince

Its final home would be a Jerry Bates SBD Dauntless (85" wing). But since that is a project that will not start until this winter I have time for such decisions. One idea I was playing with would be to mount it on my Kangke DGA-15 to break in the engine and have it ready when the Dauntless is ready.

The specs on the plans gives a weight for the Dauntless of 18-24#. Since I will be adding such things as cockpit, scale details, retracts (and a heavy engine) I expect I will be on the high side of the weight range, if not slightly more than 24#.

Tom

Radial power

Hello tdevince,

first of all let me say that I do not have a FR7-420 (even though I plan to get one sooner or later), but I do have the older FR5-300 that I've bench run quite some times and that I intend to eventually install on a warbird. I don't know how relevant my experience with the FR5-300 can be in relation to the FR7-420, so take this for what is worth.
I also saw your other thread in the OS support section, but since there's currently no reply to that I'll start with the breather question. Despite what can be read in the FR5-300 manual, the engine only has a single drain nipple at the bottom. No side breather as indicated in the instructions, so my situation is exactly the same as yours, except that my manual is even less clear I run my engine with the drain plug closed since I can't see any drawback in doing so. The front crankshaft bearing is a single shielded bearing, so it cannot hold any pressure behind it. Even if the drain plug is closed, any blow-by gas that gets to the crankcase will easily flow out through the front bearing, so no pressure buildup can occur in the crankcase. This has a good side effect in that I often find a little bit of oil that has dripped down from the front bearing after a run. This is a sure sign that oil is getting to the front section of the crankcase, thus lubricating the cam rings, cam gears and tappets.
If the FR7-420 uses the same shielded (not sealed) front bearing, then I'd run it with the drain plug closed.

Prop selection, RPM and power: this obviously changes quite a bit when the displacement increases by 40% With my engine I initially used a 20x10 prop during the break-in, but I quickly found out that it was too much prop, at least for a not-yet-run-in engine. With the MenzS 20x10 I could barely get 6500rpm, and the engine was difficult to tune. Then I switched to a MenzS 20x8 and the rpm figures jumped to well over 7000rpm, eventually reaching 7500rpm with the engine fully leaned out. I expect these figures to improve even further, at least by a little bit. I may even try again the 20x10 to see if the situation has improved, or at least switch to a 20x9 if I can get hold of it (no one carries that size...).
With the FR7-420, a 22x10 is at the bottom end of the prop range. Based on my experience above, it should be a good prop for the break-in phase, but use a tachometer to make sure that you don't get too close to the engine's maximum recommended speed of 7000rpm. My understanding is that the FR7-420 is not as rev-happy as the FR5-300, but it's much torquier. While my engine didn't seem too happy turning less than 7000rpm at full throttle, most likely the FR7 will easily handle props that result in at least 6000rpm at full throttle. Maybe it could even digest "heavier" props resulting in sub-6000rpm full throttle speeds, I don't know. Personally I'd choose a prop to try and keep the ground rpm in the 6000 to 6500 range and start from there.
As for having the power to haul a 24 pound bird, on youtube you can find quite a few videos of warbirds powered by either the ASP-400 or the Saito FA-325R5 radials, and quite a few of these fall in the same weight category. Take a look at this video, for example:


The Top flite giant corsair should start right at 24 pounds, and it doesn't look like it's underpowered. And you can find many more videos like this with different warbird / engine combos. Given that the FR7-420 is larger than either the ASP 400 and the Saito FA325R5, I'd say that power should not be a problem

Now for some general observations. You may find that the rocker boxes of the upper cylinders tend to dry out, as the oil drains down by gravity. This is not an issue with my Saito FA-90TS flat twin (and, I suspect, should not be an issue with your FT-160 either), but be aware that a radial is different. You may need to periodically add some oil up there.

I'm sure that you know this, but before you first start up the engine, make sure it's well lubed. Inject quite a bit of oil through the drain nipple and, maybe, through the glow plug holes as well. Also oil all rockers. Tilt the engine around to try and distribute the oil as much as possible and then turn the engine over to further distribute it. Finally drain the excess oil.
Also, another obvious point: after run oil. With my FA-90TS I never used after run and I never had any problem. With the FR5-300 when I did the same I was rewarded with rusty bearings. Perhaps it's the fact that in a radial the crankcase volume remains more or less constant, so there is very little breathing that takes place when compared to a single or a boxer twin. This reduced breathing might promote an accumulation of acids and moisture that could be the cause of the rusting I got. Even if the FR7-420 is advertised as being "plated to resist corrosion", I'd take no chance and thoroughly oil the engine after each session.

I'd suggest checking the valves before starting the engine for the first time, even if they should have beed adjusted at the factory.
When you adjust the valve lash on a radial with a "classic" cam setup (like the OS radials), you have to be aware of a small idiosincrasy of such a setup. The cam rings in these engines have a number of reparate lobes on each ring. The 5 cylinder FR5-300 has 3 lobes per ring, while the 7 cylinder FR7-420 has 4 lobes per ring. in the case of the FR7-420 this means that when the crankshaft makes 2 complete rotations, the cam rings only rotate by 90 degrees to engage the next set of lobes. This also means that there are 4 sets of "lands" between the lobes in these rings. Due to manufacturing tolerances, these lands may not be perfectly identical, and since these lands represent the positions where valves are closed and where one adjusts the valve lash, you may find that if you adjust the lash of, say, cylinder #1 with the crankshaft at TDC, then if you turn the crankshaft through 2 complete revolution the lash may no longer be correct. Adjust it again in this new position and turn the crankshaft 2 more revolutions and, again, it may no longer be correct.
What I do is find the "land" that results in the smallest amount of lash for each valve and adjust on that land. In my case, since my engine only has 3 lobes (and 3 lands) per cam ring, after adjusting a valve I turn the crankshaft 6 times (3 x 2) and check again the valve on the same cam ring position. In your case you'd have to turn the crankshaft 8 times (4 x 2) and then recheck. The reason I use the tightest location is that if I adjust for that location, then all other points on the cam gear will have more lash than that. Too much lash can reduce power, but too little can result in a valve not closing completely and thus burning out. Also notice that the tightest "land" for the intake valves may not be the same land that produces the tightest lash on the exhaust valves, so I suggest finding the "tightest" land for each valve individually, just to be safe.

Glow plug heating. Now, I use a scratch built system to light up the plugs on my radial, so I had to go through quite a learning curve before I could get reasonable results. And there is still ample room for improvement.
The main point is that you have 7 OS F plugs to light up at once. Each plug needs around 3A at 1.5V to properly light up, but if it's drowned with fuel and oil it may take well over 4A to clear out. Possibly close to 5A. That means that your glow driver must be able to provide al teast 7 x 3 = 21A of current. That's a lot of current, and any resistence in the wiring can result in a substantial voltage drop, which can then prevent the plugs from lighting up.
If you want to use a commercial glow driver, then you need to make sure that you use a BEEFY battery and short, THICK wiring. If you want to scratch build the glow plug heating system, then I can go into more details about what I did and what I plan to do.
The bottom line is: if you have trouble getting all cylinders to fire reliably even with glow heating on, most likely your glow driver setup is the culprit. In this case you can try using a regular, single cylinder glow igniter on the offending cylinder and see if the situation improves. If it does, then make sure that the glow driver battery is fully charged and try measuring the battery voltage while it's feeding the plugs. If it drops substantially, then you may need a larger battery. If the battery voltage does not drop significantly under load but the engine still refuses to run on all cylinders, then maybe the system itself is not strong enough.

Finally, I'd say that before taking to the air, it would be wise to change all the plugs even if they still seem to work ok. This is because during the break-in process the engine may produce fine metal particles that could degrade the plugs. So changing them before the first flight should be a (not so) cheap insurance

tdevince

Radial,
Wow, Thank you for such an in depth response. It's greatly appreciated!!

Tom

Radial power

My pleasure

I myself have a small program that periodically checks Tower Hobbies' price for the FR7-420 and, if it detects a change, it sends me an email. But since last May (when I wrote that program) no price changes, so I'm still waiting...

If I may ask, if and when you get the engine, could you post your findings? As you have found there's a near-complete lack of real world experience with the FR7-420 on the internet. If you could post your experience, maybe some prop / rpm figures and the like I, think it would be much appreciated.

redball8

My Feedback: (128)

Sheesh. Just get an Evolution 777 and be done with it!

tdevince

I definitely will post what I experience if I get one.

If I wanted an Evolution 7-77, I'd be asking about the Evolution 7-77. That's why I'm asking about the OS, because I'm interested in the OS. I thought that would have been obvious.

Radial power

Thank you very much.

Oh, and another couple of little things that I forgot: these multicylinder engines have a lot of metal to warm up when compared to a single cylinder engine with the same displacement. And they also have much more cooling fin area to dissipate heat. So don't be surprised if the engine takes a while to fully warm up.

For the first runs I'd avoid using exhaust collector rings and instead I'd run the engine on a test stand with the 7 independent exhaust pipes. This way it's much easier to see if a cylinder is not firing: you only need to place your hand an inch or so behind the outlet of each exhaust stack and feel whether the pulses coming out of the stack are crisp, "hard" and hot exhaust pulses (indicating that the cylinder is firing) or much weaker lukewarm "puffs" (indicating that the cylinder is not firing). You can always fit a collector ring at a later time if you want to, when you are sure that you do not have problems with dropping cylinders.