optech

My Feedback: (9)

Was I even talking to you???

Why do I have to come from under a rock because I'm not familiar with some yesteryear ignition. Its not like they produced anything unique or earth shattering. Coming from the UAS industry I've played with a lot of engines, some seriously sexy, over the last "20 years" and not one came with or used a CH. The last CH I played with came on a second hand Fox twin I bought. It worked sorta okay but I replaced it with a more modern one and moved on. About two-three years ago I bought some spark cap stuff from CH and pics on the web site were still the old, clunky, hob cobbled looking ignitions or the new ign which was..... an (overpriced) RCexl. So you'll excuse me if CH has been nothing but an afterthought.

I know Adrian is not building RCexls so if something is new, Great! lets hear about it without the grumpy ole' fart input shall we?

Pull Up Now!

My Feedback: (3)

Yeah the stiffer material returns to neutral deflection on it's own, w/o the spring. The tradeoff is not as much pumping, but it works. I think they're either blue or black mylar or sometimes acetate.
Rick

Antique

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There's an education coming .....

optech

My Feedback: (9)

Like Adrian said, the rep was quoted as saying they use a plastic that has enough "spring back" when the pressure is gone to provide the pumping action. He also said that they have springs available should the plastic return not be enough for your application.

Later,
Mike

optech

My Feedback: (9)

Adrian,

Sounds interesting. Being non-potted, will they handle the vibration in a gasser helicopter? Small and low pwr consumption is always desirable but man, they sure take a beating.

I'm always up for trying something new and would love to take you up on the sample offer. But I'd feel more comfortable paying for it in case I can't get to it right away.

Mike

Jezmo

WOW, and just to think, the circuitry in the RCexl is the same as the more modern CH. It's funny how perception works. I am very thankful that Bill and Terry helped bring us into the modern age of Gassers.

w8ye

My Feedback: (16)

You are still under that old rock?

Come out and enjoy what the world has to offer?

Adrain will help introduce you to present day ignitions

RTK

My Feedback: (1)

RCexl is just a lesser copy of the CH ignition. I sure hope the CH and their timing curves come back on the market.

CH Ignitions

My Feedback: (11)

tkg

My Feedback: (1)

Oh I'm around for questions.
BTW CH units were potted with a special goo. Worked very well in high vibration environments, but could be easily removed for repairs and then repotted. It just was not poured full of epoxy.
More BTW CH started using the SS (computer timing) unit about 15 years ago. The original MK1 unit was fantastic, the MKII used the same program but was surface mounted. The MKIII and the MKIV were surface mounted but had multiple programs in each chip. The MKIII had 2 programs and the MKIV had 4 programs. We could select the correct program for the engine being used. That selection is why the CH units worked so well on "difficult" engines

Jezmo

How do you tell which you have Terry? MKII, III or IV.

tkg

My Feedback: (1)

The MKIII has a land in the upper right corner that you cut to change programs. The MKIV has 3 solider pads that you could jumper to change peograms. I don't remember which was what. The MKII has zip.

Jezmo

Thanks Terry.

Ed Vollmer

My Feedback: (14)

Here is the key to unlock the four maps.

It amazes me that you remember all this stuff, Terry, I sure don't.

Ed V.

Pull Up Now!

My Feedback: (3)

It's been a while since anyone has posted here, so I thought I'd wish everyone a Happy New Year! Holidays were hectic, so not much got done in the way of RC. stuff. I was totally preoccupied with rebuilding my now 19.5lb scratch Steen Skybolt from Dario Brisghella plans. It has remaidened sucessfully. Now, am continuing work on an engine I previously and mysteriously referred to earlier in this thread. It's not glow-to-gas, but I imagine this diversion can be tolerated, especially since some of the challenges of mounting electronic ignitions are common. That is the Homelite XL12 Chainsaw 54cc chainsaw engine. Pictures attached. What plane is it for? I recently located an OLD Sig Sundancer biplane ARF and put some $$ down on it. It's a 18 lb plane, and I feel fortunate for having located this extinct bird. Next up-another Saito 150 gas conversion. The first one still runs well after 2 years, starts every time, and has plenty of power. One thing I do notice is there doesn't seem to be much static compression, but it still starts every time and runs fine. In fact, the compression is so low after sitting that it feels like the valve springs are broken. Yet it runs fine. Theories on that?? Speaking of power, has anyone done any experiments with dynos for these conversions? Seems like they have a bit less power than nitro, and it would be nice to measure the HP more accurately. Also, I've recently gotten into telemetry so I can measure in-flight head temperature. I think this is very important, as we're dealing with gasoline here. I am using a Spektrum DX8 with a TM1000 telemetry transmitter. Hasn't flown yet, but I'm setting it up as we speak. I've measure head temperature on the ground after a good WOT run, and measured temps ranging from 275 to 305 degs F. Using the wrong fuel, I've seen these engines overheat in the air. Probably from over-revving, but It will be nice to see what happens in flight.

gkamysz

My Feedback: (19)

Cutting chamfer that wide with the side of the tool is cheating

CH Ignitions

My Feedback: (11)

What ever it works...LOL,

I am working now on a conversion of a RCV 91CD to gas and CH ignition and so far all looks ok,
Have to find some time to time it, Have to look at the port degree to see when it gets to the Spark plug side and figure from there.

I will let you know how it runs....If it runs.

Pull Up Now!

My Feedback: (3)

Even though that 4 stroke is a rotary valve motor, you're still going to fire every revolutionone in the exhaust and the one that countsthe compression stroke. So with respect to the timing, it really doesn't matter, right? What effect would the port timing duration and location have on any timing modification one might contemplate? Isn't the typical 28-32 degs timing more a matter of flame speed and piston speed physics? What are your thoughts on that Adrian?

CH Ignitions

My Feedback: (11)

Yes you right, I am curious my self how it will work . The spark plug is 180 degree from the exhaust . I have to see now at what degree the port in the rotarry cylinder will start to open in the sparkplug position.
Imade the carb addaptor, timing ring on the hub and I let the timing part the last. But I will make it to work...one way or another.
I have couple things Imy like to talk with you , Iwill email you this week .Iallways value your opinion.

Thanks
Adrian

P.S.

I went to bed and I could not sleep...thinking about...so I jump out and opened the engine and watch the piston relation with Cylinder opening port. I did not put a degree wheel on it but Port opens on the SPK fron like 10 -15 degree after BTDC and stay open 5-ish after TDC .

So YES can be easy done, the waist spark will actualy be "closed' between SPK and Rotary Cylinder.. Ihope to start it this weekend if I have time.


Adrian

gkamysz

My Feedback: (19)

RCV uses the same setup for the own spark ignition engines. Nothing to worry about.

Gordon W

Hi guys. I've read all of this thread and would like to thank everyone for all the information I've gleaned from it. Right now I'm in the process of converting a Laser 240V to gas from glow ignition. As the photos show, the engine is a four-stroke 90 degree vee twin with one carb per 20cc cylinder. The beauty of this powerful engine is that it has a very low level of vibration, making it ideal for use in a wire-braced biplane. With glow ignition it's pretty thirsty and dispenses the usual large quantity of oil, which is why I want to convert it to gas, and I have a couple of questions about that.

Whilst a flat twin can use one dual-output ignition unit, this conversion needs two single ignition units each with its own sensor. The sensors are mounted on the crankshaft housing spaced at 90deg round the shaft, and a single magnet is mounted on the prop driver. I'm using two Rcexl ignitions, with the sensors mounted on a split ring clamp on the tapered and ribbed crankshaft housing.

For mounting the sensors and magnet I turned up a couple of aluminium ring clamps on my old Unimat 3 lathe. The rings are split and are secured by pinch-bolts. Photo 1 shows these rings. The left-hand ring fits the prop-driver and carries the magnet. The right-hand one has internal steps, which clamp on successive ribs on the crank housing. Also visible are the slits in the rings, the pinch bolt positions, and the sensor mounts screwed in place.

Photo 2 illustrates the ribbed crankshaft housing, and the prop driver in which the groove makes securing a magnet difficult.

Photo 3 has the rings and sensors in place. The magnet is a force-fit in its ring. The two grooves on the magnet ring are at 28 degrees spacing, which is the spark advance figure specified in the Rcexl instructions. When the groove at the rear of the magnet just exits from beneath a sensor, the attached ignition unit then activates to produce a spark at the appropriate time for the plug it's controlling. The second groove, which follows 28 degrees later, is set to TDC on No 1 cylinder when it is just exiting the sensor for No1 cylinder.

Photo 4 shows that the sensor installation is quite neat.

Initially I bench ran the engine to get used to adjusting two carbs, first on spark ignition and Laser mix glow fuel, and after half a gallon had gone through the engine I changed to 20:1 petrol:Evolution oil. At present the engine has the original Laser carbs. These were reasonably easy to set up on petrol for reliable running from idle to max revs with smooth transition through the range, though the main needles are very sensitive with only 1/4 turn between rich and lean, as is normal with glow carbs on petrol. Photos 5 and 6 show the test bench, and you can see that unlike the Japanese 4-strokes, the Laser carbs are mounted on the cylinder heads.

Photo 7 is the Laser 240V installed in my 27.5% scratch-built Jungmeister, along with its ignition system The two Rcxel units are secured with Velcro and a tie-wrap onto a liteply shelf, and an 8A Ubec atop that provides the 5V supply. The tortuous route of the plug leads keeps them well away from the hot silencers.

The underside view in the Photo 8 shows the fuel lines and the crankcase breather outlet, with its yellow/green flagged stopper to prevent drips on the hangar floor. The yellow Tygon tube pointing towards the prop-driver is the fuel tank vent, oriented forward as per the Laser instructions.

Photo 9 shows the engine fitting easily insie the cowl without having to cut holes for the plug caps.

Now comes my request for advice. When I bench ran the engine on ignition and gas, it handled really nicely. When mounted in the Jungmeister, it was again very tractable ….. until I pointed the fuselage nose-up, when the engine stopped every time. No matter how I adjusted the carbs, it always stopped. So clearly it needs a means of ensuring a constant head of fuel at the carb. Is it likely that simply pressurising the tank from one or both mufflers will suffice? Or should I fit a pair of proper gas pumper carbs?

As the engine is 20cc per cylinder, a carb sized for that capacity with induction pulse pump operation sounds as if it ought to do the job. However, I see that the Walbro WT-456-1 is now discontinued, but the Zama C1Q-P8-8YA has been identified as a viable substitute. Do you guys think that I ought to have a reasonable chance of success with a pair of Zamas?

Thanks

Gordon

RTK

My Feedback: (1)

...

CH Ignitions

My Feedback: (11)

Hi Gordon,

I have to say that you did a real nice job. I have a Enya VT240 that I want to convert to gas. Zama is a good carb I have use it in many conversions on RCV91CD, Saito 120,125,150,180. And it works real good. It is a direct replacement of WT-456-1.
Bad part is that both are discontinued but still available.
What I want to do in mine is to make an Intake and run one carb. Looking at your setup it will be hard to set 2 carbs in that small space.
Any way it will "fill" one cylinder at the time and will be enough with one carb.
Check around and you may find some old stock .


Thank You
Adrian

triumphman49

My Feedback: (149)

Hello Gordon and a big hello to Adrian,

Was wondering if you might consider using a Cline or Iron Bay regulator to assist in constant fuel flo to the stock carbs.

T-man49 in Al
Club Saito 723

SrTelemaster150

There is a way to insure adequate exhaust valve lubrication.

Purchase a set of check valves W/inlet filter screen. P#SAI130T68A


Screw the inlet valve into the back plate, drill & tap the cam housing for the outlet, run a line from the outlet to the exhaust rocker cover that is D&T'ed for breather nipples (you will need 3 additional nipples besides the one from the backplate that was replaced by the inlet valve) P#SAI6519



Run an additional line to the inlet rocker box & then vent to the atmosphere. If you need the crankcase pressure to pressurise your fuel tank, run the pressure line through a bleed valve to allow some pressure to vent to atmosphere. P#SAI300TTDP102


This will assure that all excess oil from the crankcase reaches the cam, tappets, cam gear, then the exhaust valve stem and just for good measure, the intake exhaust stem.

If you run the engine inverted, you can probably eliminate the lines to the rocker boxes as plenty of oil will likely travel down the pushrod cover tubes to lube the valves.