New Products Flash Sale
Thread Tools
Old Apr 28, 2015, 03:10 PM
stinkyfive is offline
Find More Posts by stinkyfive
VNE ? I bite my thumb at thee
stinkyfive's Avatar
Shropshire, UK
Joined Jan 2005
514 Posts
Discussion
OS 33 GT ignition module

Hi all,

I've searched high and low and it seems that OS use a unique timing protocol for their engines, which means a standard RCEXL ignition module won't work with the magnet in it's current location.

Is there a dodge round this, or do I have to shell out the massively inflated amount OS want for their proprietary unit, which I believe is made by RCEXL anyway.

Thanks in advance, Ell.
stinkyfive is offline Find More Posts by stinkyfive
Reply With Quote
Sign up now
to remove ads between posts
Old Apr 28, 2015, 05:55 PM
ZAGNUT is offline
Find More Posts by ZAGNUT
supreme being of leisure
ZAGNUT's Avatar
Tel Aviv, Israel
Joined Jul 2004
3,014 Posts
either drill new holes for the sensor or get one of the sensor mounts that allows a higher range of adjustment. the one that should come stock with the garden variety RCEXL has 4 large slots and there is also someone selling a hose clamp version. zip ties also work, here's a photo i've seen before:
ZAGNUT is offline Find More Posts by ZAGNUT
Reply With Quote
Old Apr 28, 2015, 11:06 PM
Brutus1967 is online now
Find More Posts by Brutus1967
I convince things to work
The Netherlands
Joined Nov 2009
4,037 Posts
Is the timing angle different? or does it just not spark?

Brgds, Bert
Brutus1967 is online now Find More Posts by Brutus1967
Reply With Quote
Old Apr 29, 2015, 02:16 AM
stinkyfive is offline
Find More Posts by stinkyfive
VNE ? I bite my thumb at thee
stinkyfive's Avatar
Shropshire, UK
Joined Jan 2005
514 Posts
Thanks both,

I will try the cable tie for now.

Bert, I believe the timing angle is different in the firmware. The engine will run but there's no way it's gonna throttle past 2000 rpm.

The OS unit allows the engine to start and run backwards more easily than forwards and OS want 4 times as much for a replacement as the rcexl unit.

Ell
stinkyfive is offline Find More Posts by stinkyfive
Reply With Quote
Old Apr 29, 2015, 02:42 AM
Brutus1967 is online now
Find More Posts by Brutus1967
I convince things to work
The Netherlands
Joined Nov 2009
4,037 Posts
Quote:
Originally Posted by stinkyfive View Post
Bert, I believe the timing angle is different in the firmware. The engine will run but there's no way it's gonna throttle past 2000 rpm.
Sounds like its horribly rich, even if it is dying of fuel starvation? That sounds like a too late spark to me....

If so, a possibility is, the OS unit is triggering on the arrival of the magnetic field under the sensor, while the RceXL is for a fact triggering on the magnetic field leaving the sensor.

Either the sensor is reversed (meaning, the OS gives a high where the RceXL gives a low) and in that case just maintaining the OS sensor would do the trick, but that is not very likely, so what I would do is fit a pulse inverter (simple transistor and a few resistors, that turn the pulse upside down).

The RceXL triggers on the pulse going from low to high, and that happens when the field leaves the sensor. Inverting the pulse, makes the puls go from low to high when the field arrives at the sensor, which would typically be 20 or so degrees earlier, and those 20 degrees can cause the running exactly as you describe....

In my opinion, there is a good possibility that would do the trick, since the timing curves for most engines are near identical, or at least, not THAT different that one engine would not run on a different ignition.

Brgds, Bert
Brutus1967 is online now Find More Posts by Brutus1967
Reply With Quote
Old Apr 29, 2015, 03:23 AM
ClippedWings is offline
Find More Posts by ClippedWings
Registered User
Australia, NSW, Killara
Joined Jun 2013
102 Posts
Quote:
Originally Posted by stinkyfive View Post
Hi all,

I've searched high and low and it seems that OS use a unique timing protocol for their engines, which means a standard RCEXL ignition module won't work with the magnet in it's current location.

Is there a dodge round this, or do I have to shell out the massively inflated amount OS want for their proprietary unit, which I believe is made by RCEXL anyway.

Thanks in advance, Ell.
I don't think the sensor position in relation to the magnet is different but the advance characteristics were changed and are unique to OS (which is why they run backwards). I have an OS GT33 and will check the magnet/sensor position later when I get home.
ClippedWings is offline Find More Posts by ClippedWings
Reply With Quote
Old Apr 29, 2015, 03:53 AM
ZAGNUT is offline
Find More Posts by ZAGNUT
supreme being of leisure
ZAGNUT's Avatar
Tel Aviv, Israel
Joined Jul 2004
3,014 Posts
is it possible that OS is doing like the euro ignitions and setting the sensor to the retarded position and actually advancing in the firmware? RCEXL, CH and others took the easy way by setting the sensor fully advanced and adding in delay to retard the spark at lower RPM.

to me that would explain why they start so easily backwards. back when i used 3W ignitions on converted engines i could get the same if the pick up coil wasn't advanced enough....
ZAGNUT is offline Find More Posts by ZAGNUT
Reply With Quote
Old Apr 29, 2015, 04:36 AM
Brutus1967 is online now
Find More Posts by Brutus1967
I convince things to work
The Netherlands
Joined Nov 2009
4,037 Posts
If they run backwards, then most likely my assumption is true: The ignition triggering on the arrival of the magnetic field: Only that configuration would allow for a spark to be triggered in the reverse direction at the approximately correct timing....

The RceXL, with the pulse and magnet-angle chosen by the designers, triggers a spark at say, 28 degrees BTDC in the normal running direction, but in the reverse direction at 28 degrees PLUS the width of the magnetic field AFTER TDC. That will never run reversed.
The OS running backwards more or less proves that it triggers on the arrival of the field, and when you run that configuration backwards, it will still most likely spark before TDC in reverse direction.

Like I said before, just invert the pulse coming from the RceXL ignition before it goes into the module (with a transistor and a couple of resistors, there are plenty circuit diagrams of pulse inverters out there) and your engine will run with an RceXL unit....

If you want to be sure: hook up a LED or a voltmeter to the sensor, and see at what angle it triggers (should be just 28 degrees, like all others), and if that is the arriving or the leaving of the field, and if it is on the rising or falling flank of the signal....
Then check what your RceXK sensor does at that exact angle.... invert as needed.


Brgds, Bert
Brutus1967 is online now Find More Posts by Brutus1967
Last edited by Brutus1967; Apr 29, 2015 at 04:41 AM.
Reply With Quote
Old Apr 29, 2015, 04:45 AM
Brutus1967 is online now
Find More Posts by Brutus1967
I convince things to work
The Netherlands
Joined Nov 2009
4,037 Posts
Quote:
Originally Posted by ZAGNUT View Post
is it possible that OS is doing like the euro ignitions and setting the sensor to the retarded position and actually advancing in the firmware?
To me, that sounds like they have invented future-telling (fortune telling) software.....

It would mean that the actual spark is always the result of the previous revolution....

You can delay the spark AFTER a trigger signal, but you cannot, simply CANNOT advance a spark to BEFORE the trigger signal.... negative time does not exist, telling the future does not exist time travel does not exist....

Brgds, Bert
Brutus1967 is online now Find More Posts by Brutus1967
Reply With Quote
Old Apr 29, 2015, 05:15 AM
ZAGNUT is offline
Find More Posts by ZAGNUT
supreme being of leisure
ZAGNUT's Avatar
Tel Aviv, Israel
Joined Jul 2004
3,014 Posts
Quote:
Originally Posted by Brutus1967 View Post
To me, that sounds like they have invented future-telling (fortune telling) software.....

It would mean that the actual spark is always the result of the previous revolution....


You can delay the spark AFTER a trigger signal, but you cannot, simply CANNOT advance a spark to BEFORE the trigger signal.... negative time does not exist, telling the future does not exist time travel does not exist....

Brgds, Bert
yes, that's how they do it. firmware must be a PITA. the DA and older 3W were using an inductive pick up coil with a tear drop shape to advance the trigger point as RPM increased.

there is also this programmable module that lets you put the sensor wherever you want: http://ignitionmaster.com/ don't think he's actually selling though, poor guy is paranoid that someone will clone it...telling him that it can still be copied with the security fuse turned on didn't seem to help.
ZAGNUT is offline Find More Posts by ZAGNUT
Reply With Quote
Old Apr 29, 2015, 05:32 AM
AA5BY is online now
Find More Posts by AA5BY
Registered User
AA5BY's Avatar
East Texas
Joined Aug 2007
1,861 Posts
Have you tried another ignition yet? A friend had problems with his and borrowed a RCexl ignition from one of his DLE engines and it ran fine on it.
AA5BY is online now Find More Posts by AA5BY
Reply With Quote
Old Apr 29, 2015, 05:51 AM
ClippedWings is offline
Find More Posts by ClippedWings
Registered User
Australia, NSW, Killara
Joined Jun 2013
102 Posts
OK just had a look at my OS GT33, the magnet goes past the sensor very close to TDC. It was only a visual measure but the angle is nowhere around 28 degrees BTDC it is more like 0 - 5 degrees BTDC.
If replacing IM one should turn the sensor clockwise if the propeller is in front or left if you are looking from behind the propeller. The sensor did not seem to have enough room to move for a 28 degrees gap so repositioning as suggested may be required..
ClippedWings is offline Find More Posts by ClippedWings
Reply With Quote
Old Apr 29, 2015, 05:53 AM
Brutus1967 is online now
Find More Posts by Brutus1967
I convince things to work
The Netherlands
Joined Nov 2009
4,037 Posts
Quote:
Originally Posted by ZAGNUT View Post
there is also this programmable module that lets you put the sensor wherever you want: http://ignitionmaster.com/ don't think he's actually selling though, poor guy is paranoid that someone will clone it...telling him that it can still be copied with the security fuse turned on didn't seem to help.
I know him (not in person, he is Dutch and member of a forum I'm on as well), and when I was busy with the first prototypes of my backplate sensor (inductive proximity switching) he did provide some assistance.

But along the way, it got a bit confusing, one time it would look like he knew exatly what he was doing, the next time he made errors and mistakes that even me, with my very limited knowledge of practical circuitry building could see as completely off the charts wrong.... Not only in circuitry, but also in advancement curves and the likes....

But the strange thing is, he offered to sell me one of his processors, as according to him it was relatively simple to extract the processor of an RceXL unit, and replace it with his processor, after which the RceXL would be fully programmable over Bluetooth....

I guess, he sells, but as a complete system including installation....

Anyway, you are not completely free in the placement of his sensor: it should be between 30 and 60 degrees before the earliest point of actual triggering....

Brgds, Bert
Brutus1967 is online now Find More Posts by Brutus1967
Reply With Quote
Old Apr 29, 2015, 06:19 AM
Brutus1967 is online now
Find More Posts by Brutus1967
I convince things to work
The Netherlands
Joined Nov 2009
4,037 Posts
Quote:
Originally Posted by ClippedWings View Post
OK just had a look at my OS GT33, the magnet goes past the sensor very close to TDC. It was only a visual measure but the angle is nowhere around 28 degrees BTDC it is more like 0 - 5 degrees BTDC.
If replacing IM one should turn the sensor clockwise if the propeller is in front or left if you are looking from behind the propeller. The sensor did not seem to have enough room to move for a 28 degrees gap so repositioning as suggested may be required..
What you describe, is exactly what allows the motor to run both ways, since ignition timing does not vary much in either direction.

Then please try my suggestion, and connect a voltmeter between black and white on the sensor leads. The sensor triggers when the magnet approaches the sensor, NOT when it is centered under the sensor. it triggers again but the other way, when the flied leaves the sensor.
The ignition unit is programmed to respond to only ONE of these trigger points.
Very big chance you see the meter jump (either high to low or low to high) at 28 degrees before TDC instead of very close to it. No idea which way it jumps with the original OS sensor, but I AM 100% sure, the RceXL sensor jumps from high to low at exactly the same point. For the RceXL ignition unit to work correct on this engine, it needs to see a jump low to high at that point, and that you can achieve by inverting the signal.

IF the OS sensor jumps from low to high at this first point (28 deg before TDC) then most likely, your RceXL will work on the OS sensor, and the ignition unit is more or less identical to the RceXl, only the sensor and the magnet location are different in that case...

It is less than 50 cents of components to achieve this and in the past, you could simply buy servo pulse inverters (to connect Futaba servos to Graupner equipment).

Brgds, Bert
Brutus1967 is online now Find More Posts by Brutus1967
Last edited by Brutus1967; Apr 29, 2015 at 06:25 AM.
Reply With Quote
Old Apr 29, 2015, 06:38 AM
ClippedWings is offline
Find More Posts by ClippedWings
Registered User
Australia, NSW, Killara
Joined Jun 2013
102 Posts
As said, the OS GT33 does not trigger at 28 degrees BTDC.
I have many RCEXL equiped engines, in a standard RCEXL setup the magnet is well over 20 degrees past the sensor at TDC. In the case of the OS GT33 the magnet only clears the sensor at TDC (hence the 5 degrees BTDC). Even without equipment you can visually see there more than 20 degrees difference in the relative position of the magnets and sensors at TDC.
ClippedWings is offline Find More Posts by ClippedWings
Reply With Quote


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Wanted Os max gt 33 tantar Aircraft - Fuel - Engines and Accessories (FS/W) 0 Mar 26, 2015 03:26 AM
Sold New in box! OS GT-33 ljmartin44 Aircraft - Fuel - Engines and Accessories (FS/W) 0 Mar 25, 2015 11:42 PM
Sold Os 33 gt los36 Aircraft - Fuel - Engines and Accessories (FS/W) 0 Feb 27, 2015 02:50 PM
Sold OS GT 33 new in box zeus3313 Aircraft - Fuel - Engines and Accessories (FS/W) 3 Mar 10, 2014 07:08 PM
Sold Bnib os 33 gt tm77 Aircraft - Fuel - Engines and Accessories (FS/W) 2 Sep 24, 2013 10:34 AM