JieM

As far as I know, RCexl timing curves are not linear curves, but step curves. That means that the timing is at 4deg at idle to 2000rpm and after 2000rpm jumps directly to 28deg. I will try to find my source.

JM

cathurga

This is one of the older RCxel curves. Please note this is not from an official source, and if it is under copyright, I will happily remove if it caises problems.

It seems that the clever electronics in the chip, along with the presence of the 'check' magnet can figure out that the engine is at low/start revs, and retard the ignition to around 4 Deg, then at around 1500rpm-2000rpm, it starts up towards 28Deg and then advances no further after 4000rpm. Considering, most of us are getting around 6250-6500 static, which probably unloads to around 7000rpm, the timing is not advancing at all where the power should be. This is why Saito (and others) have said best performance is with the timing around 35deg. The problem is that you have to shift the ENTIRE curve, and then at low(er) rpm ranges the timing is suddenly SO advanced that it starts the pre-ignition problem, and THIS is where the damage is taking place as the engine doesnt have the inertia of the higher rpms, and the gas is ingited very early causing LARGER pressures in the combustion chamber, and the exploding gases are now competing with a rising piston....
This is just MY THEORY, but if the upper end of this curve could be set at 34 degrees instead of 28, we would probbaly get the best of both worlds...

Smotherb

cathurga

Smother, thanks for the update. I am going to have a look at my carb and see if there is anything odd going on in there. As I say, I bought a new throttle body because I thought I had broken it, but it would be nice to have a spare, functional carb that I can install quickly should the need arise, and then I have another to recondition and keep spare.

I think the warranty is a year, from date of purchase. So best to get it run in, and use it, if its going to dismantle itself, it might do it sooner rather than later...lol. I had a guy come by the field yesterday, and he was very unhappy as his brand new FG84, which he had spent hours meticulously running in, went on its maiden and siezed in-flight. He managed to get the plane down without too much damage, but the engine was totalled....from the pics he had, looks like the main crank bearing failed. The Fg84 did not have the bronze bushing, so might have been that. he was quite fastidious with his prep, so doubt it was any fault of his own. Unfortunately, he bought his years ago, and has only recently managed to get it in the plane he was building, and as a result, no warranty whatsoever.
If your has all the new gubbins, you will hopefully be free of troubles. It would be interesting to see if they have made any changes to the timing... the new pistons will result in lower compression, and the new cylinders have more 'meat' on the mounting areas so should not be prone to cracking as easily....I wish you all the best of luck!

As for Frankensaito, we did 2 more great flights yesterday, the ambient temps were in the low/mid 40Deg C,so really warm, and that was at sunset! We have put the cowl back on, and the last 2 flights the temps were getting up into mid 170C, which is high...so we removed the fake exhaust stacks from either side of the fuse, and this opened up the cowl with 2 large exits, that are placed in such away that they create negative pressure and draw air out. Big difference. Highest temp recorded yesterday was 162C, its still a little high, but that was only for a short burst...mostly hanging around 150C for most of the flight. Where we did the opening cowl mods, after the flight, with the nose pointed into the wind, you could feel a lot of warm air being removed by the wind, so it is definately doing the cooling job.
Again, very very economical engine, got 2 x8 min flights and there was probably enough in a 500ml tank to secure you 3 x 7min flights.

Here are a few vids....again, sorry for the wind noise, and the light was getting low so quality is down....

ForcesR

Cathurga, the photos you viewed of your friend's FG84R3 destruction, did the Master Rod look similar to this one?

cathurga

foundryratjim

My Feedback: (93)

Same 4-bladed prop, running 93 octane fuel, 30:1 Stihl HP oil....[/QUOTE]

Great flying and video. Beautiful flying site!

ptallman

My Feedback: (28)

Hi all,

I lost one of my spring clips that holds the spark plug cap on. I can't seem to find where I can get a replacement, anyone know?

Thanks,

Phil

cathurga

ForcesR

The photo shows a FG90R3 Master Rod, failure was due to over revving in flight. The recommended 24 x 10 prop was used but the mistake was made during ground tuning, the maximum RPM should have been left at 6500rpm but the HSN was leaned until 6700rpm was reached. During full throttle in flight the prop unloaded and the RPM went well above 7000rpm which caused the Master Rod to fail which caused catastrophic internal failure in the engine. If a 24 X 12 prop is used and the maximum ground RPM is set no higher than 6500rpm, the engine should not, will not over rev in flight thus no Master Rod failure, no destroyed engine to use as a boat anchor or door stop. The mistake was an expensive lesson to learn what one can and cannot due concerning Radial engine maximum RPM setting/tuning.

cathurga

elmshoot

My Feedback: (6)

Roll ypur own.
On the Kelo exhaust the caps wont fit correctly anyway. I drilled a 1/16" hole in the rear fin and safety wired the cap on.
Sparky

ForcesR

The lesson I've learned from my experience is not to exceed 6500rpm at full throttle during ground run HSN adjustment on the Saito FG90R3, FG84R3 and FG60R3 radials to prevent in flight over revving of the engine. Allowing the engine to rev above 7000rpm at full throttle in flight will eventually lead to failure of the Master Rod which in turn leads to catastrophic internal failure of the engine.

cathurga

lolo396

Hello,

I regularly read this forum, but this is my first intervention to share my experience.
You can see on this graph the engine RPM on the ground and during the flight with a Mejzlik 22 x 10 :



6350 RPM on ground and more than 7300 during the flight. Is it too much ?
My engine is an FG 60-R3 on which I moved the magnets of the original propeller hub to have 30 degrees BTCD on each cylinder

EFHANC

Seems a RPM REV LIMITER would have saved a few engines .

cathurga

I dont know if the revs you are getting is going to torch your engine, but it might be a good idea to try something with a little more pitch, and see what happens. I see there are limited vendors of 22x21, but there are a few, maybe worth trying them out and see what the handling is like, and the revs.
We dont have a rev counter on our test plane, well we do, but its onboard only and doesnt store revs, so I cannot tell you what revs we are getting in flight. I know that it does around 5400-5500 on the ground, and is quite happy doing so. As mentioned before, these engines are 4T and they like a little more pitch....

I dont know about rev limiters saving engines, but from my deduction, Saito are trying to squeeze as much 'power' out of these engines as they can, as the 'popular' perception is that more revs is better....hence the aggressive advancement on the timing from factory....

Just by the way, those videos I put up, the takeoff on that plane is always at about half throttle, for the simple reason is that the inboard gear doors dont close properly at speed, so the take off is slow, no flaps and then when the wheels are tucked away safely, the throttle goes up. We are fortunate that we have a nice long runway to do that with, and understand why some would want more grunt on take off.

duxford

I have a Saito FG R33 which went into self destruct after running in and a couple of flights. Morris Mini Motors completely rebuilt the engine with all the mods and now runs a lot better. It seems there is a common fault in all of Saito radials, I never contacted Mcgregor Industries in England regarding the problems as I have had dealings with them before. My engine is installed in a 1/4 scale Sopwith Pup but around half throttle it ran like it sounded rich, I managed to find out that due to atmospherics within the cowl it would upset the carb and to overcome this I removed the plate on top of the carb where their is a small hole which I drilled out and tapped a 2mm hole and installed an exhaust nipple I then attached some fuel tube and drilled a 3mm hole in the top and bottom of a 35mm film canister thus sucking in smooth air, the canister is placed within the fuselage. This trick as been around for a long while.

cathurga

Its not so much a common fault, its just that Saito thought that converting engines designed for glow, is as simple as adding an ignition system, and changing the carb, and hey presto! New line of gas engines.. It is not impossible that it could work, as many people are doing the conversion of glow engines by getting new carbs, ignition systems and doing it successfully. The biggest differences being that they need to have a higer than normal fuelil ratio than gas engines normally have. In most cases, this is 20:1 as opposed to 2T engines that are running 30:1, 40:1 and in some cases, successfully on 50:1. The reason is that there is no lubrication APART from what blows by the piston rings. In theory, there is nothing wrong with this, and it seems to work in many cases BUT it also means that many engines are getting a lot of carbon build up on the valves (exhaust mainly) and in the combustion chamber. The engines are NOT able to burn off all the oil as they NEED excess oil to blow by. Problem is, most of these oils are going past the HOT exhaust, and sticking to it, causing build up.
I have been looking into some 4T engines that have been designed from the ground up, as gas engines. One of them is the NGH range. The NGH38 is an interesting one, it has a series of breather pipes from the backplate to the carb and inlet manifold. They seem to be using crankcase pressure to run the carb, and distribute oil/vapour. They seem to run well and apart from a few cases of badly worn cam lobes, they seem to have operated well. Some have even admitted that they 'may' have underpropped/over-revved them which has caused valve bounce and the resulting cam wear.....NGH suggest 32:1 oil ratio for these engines.
The UMS gas radials are ALL using the crankcase to distribute fuel air mix, and they are all specified at around 30:1. They are fairly new, and not many people run them, so longevity is questionable. I know nothing about quality of materials in these, but they look great, and they have a nice range of sizes too, this will be my next radial.
The OS GF40 single gas 4T has a PCV valve type set-up that is what is regulating their lubrication, and is using crafty methods of getting the oil around the engine, and apart from one or two cases of excessive valve train wear, they seem to be good engines. The ones that have had wear problems on the rocker shafts, have cured this by avoiding over-revving. Apparently the PCV valve (ball and spring thing) was not able to open/close properly at high reves, and lubrication ability went down....result: engine wear and failure.
Saito have their radials, and they also have the single gassers (I have the FG40). The singles, like the radials, DO NOT have any method of lube APART from blow by and ALL of them require 20:1 oil. The singles do not appear to have the failure rate, and seem to be quite reliable.....and here is the kicker in my opinion... The singles are all timed around 28-30Deg BTDC....the radials at 44 Deg BTDC.....WHY?......WHY? ....WHY? The ignitions ALL run the same curve..... my guess is that they are constantly trying to appease the masses that demand MORE POWER, MORE POWER, MORE POWER.....theyre getting it, but they are also getting failures.

• UMS engines, timed at 30DegBTDC, with crankcase lube @30:1 oil ratio
• NGH engines, cranklube through breathers @30:1 oil ratio. Strangely, they time this at 40Deg BTDC from factory, but everyone running them has changed this to around 30-35Deg BTDC and they run better.
• OS engines,crankcase lube through PCV setup, timed at 30DegBTDC @30:1 ratio
• Saito Singles, timed at 30DegBTDC, blowby lube @20:1
• Saito Radials, timed at 44Deg BTDC, blowby lube @ 20:1
• FrankenSaito, timed at 30Deg BTDC, crankcase distribution lube @ 30:1

I have not looked at the Valach Engines, Kolm Engines, Laser, Roto or Moki Singles but from what I can see on their pics, all of them seem to employ either a breather pipe setup such as the NGH setup, or they are connected to the inlet somehow. I dont want to speculate on their engines, but it seems to add up to me, that lubrication is a problem, ignition timing is a problem on the Saito's. Over-revving is also going to contribute, especially if its timed wrong, and badly lubed.....although even if those to conditions are met adequately, I would not want to run the revs too high anyway....

All speculation, but it seems to add up. Some people cannot believe that the awesome people at Saito would make such a glaring error, and will stand by the expertise of Saito. I understand this and hope your engines last....

shorte

Are the new saito FG-60r3 coming with the new intake to distribute oil?

cathurga

JieM

For your information Olivier Rogeau (Modelisme Micromoteurs Service) makes some tests with a needle bearing on the master rod. This guy is a French craftman who also makes intake modification on the Saito (and other) radial series. He is very active on Facebook and is english speaking. He has also a web site (unfortunatly only in French)

A picture of his main rod modification.




JM

shorte

I wonder if it is all the heat build up ins cowls causing problems. If it was on a a stick where it stays nice and cool. It would hold up better.

cathurga

shorte

I like to have all needle bearings in rods and a big slit in them to lube them like zenoah have. I cant see spending 1200 bucks and another 500 to do the mods. No motor is worth that.