Jab engines

[kgwilson]

Yes there is a shim washer and a new one comes with the new clutch assembly. I now have 2 clutch assemblies & 2 shim washers & both look to be in perfect condition. The clutch itself looks like an encased bearing & flies out on the shaft when the starter is activated. I imagine there are 2 face plates inside it with a calibrated spring to hold it until a certain amount of torque is applied.

[kgwilson]

Having now checked up on starter types I reckon it is a Sprag clutch often used on motorbikes as there is no solenoid pre engagement mechanism which stops the clashing of teeth on the original Bendix. The starter solenoid is mounted on the firewall.

[Yenn]

I wondered why they ever had a clutch in the starter system.ts of much bigger motors start with a Bendix screw drive and no clutch. It just seems to me to be an unnecessary failure point

[facthunter]

Better the clutch than the flywheel bolts. Savage starter engagement stuffs flywheel ring gears AND tests the flywheel bolts. The best engage fully before they spin at all.. Even the Rotax 912 has starter drive issues. A lot of GA engines engage in the accessories case and you don't want bits of metal dropping off in there. IF you want to nurse your starter have the throttle closed until it's turning properly THEN open it slightly. Often it will start so gently you have difficulty knowing exactly when it started. Nev

[Thruster88]

I wondered why they ever had a clutch in the starter system.ts of much bigger motors start with a Bendix screw drive and no clutch. It just seems to me to be an unnecessary failure point

 

Every starter motor that I have seen in automotive agricultural and aviation has had a sprag clutch between the pinion gear and armature. This allows only the pinion gear to get driven by the flywheel momentarily when the engine starts preventing over speed damage.

[kgwilson]

I found my old starter bendix/clutch & compared it to the new failed one & that is when I found out what the problem is. The sprag clutches on both are perfect so it isn't that. The main drive cog which is meshed to a pinion on the starter motor rotor is attached to the bendix shaft that has the sprag clutch & throws the pinion on to the ring gear. On the first one I had, it fits on a spline but on the later one it appears to have just been pressed on without any spline. The fit has let go and spins on the shaft. Pretty poor improvement as it lasted about 120 starts. There are slight differences with the size of the sprag clutch and thrust bearing. The first one was replaced when it stopped engaging the ring gear & was just grinding at the edge of the teeth. The length dimensions of both are identical so I have never been able to figure out why the first one stopped meshing with the ring gear.

[facthunter]

The press fit is not adequate. Someone's cut corners there. Only the inertia of the starter spinning throws that pinion into mesh and any stickiness in the fast multi start throw in or tight mesh of the gear will make the engagement unreliable. Going through a reduction makes it less likely to work satisfactorily also. Nev

[Blueadventures]

I found my old starter bendix/clutch & compared it to the new failed one & that is when I found out what the problem is. The sprag clutches on both are perfect so it isn't that. The main drive cog which is meshed to a pinion on the starter motor rotor is attached to the bendix shaft that has the sprag clutch & throws the pinion on to the ring gear. On the first one I had, it fits on a spline but on the later one it appears to have just been pressed on without any spline. The fit has let go and spins on the shaft. Pretty poor improvement as it lasted about 120 starts. There are slight differences with the size of the sprag clutch and thrust bearing. The first one was replaced when it stopped engaging the ring gear & was just grinding at the edge of the teeth. The length dimensions of both are identical so I have never been able to figure out why the first one stopped meshing with the ring gear.

[ATTACH type=full" alt="20200529_135435.jpg]53585[/ATTACH]

That’s a bugger to have happen. Best part, maybe, happened at your home airfield. Would not be good mid trip. Worthy of report to RAA tech and the supplier. May be a few out there on the way to failure. Hope you can get a correct replacement. Re not engaging I guess you checked the condition of the ring gear so perhaps the shaft condition any groove wear that would allow slight tilt of the drive spline unit or maybe not lubed. Cheers and thanks for sharing.

[onetrack]

The starter clutch is a standard automotive starter clutch, is it not? It looks like someone is getting them made in China, thus the construction shortcut.

Lack of lubricant is often the main reason for starters failing to engage properly, worn bushes comes next - which is also related to lack of lubricant.

 

https://jabiru.net.au/community/engines/starter-motor-not-engaging/

 

http://www.ransclan.com/forums/showthread.php?4055-Jabiru-3300-Starter

Edited May 30, 2020 by onetrack

[kgwilson]

Just so you know, Jabiru are replacing the starter clutch & paying the freight for me to send the failed one back. They confirmed that the supplier of the one with the pressed on gear is different (& I imagine cheaper) from the original with the gear on a spline. There have been a number of the older type that eventually failed like my one did. That is it would not fully engage the ring gear when fired and the pinion just ground at the edge of the ring gear. No real damage was done though. I could not ascertain why it wouldn't as the bendix was fine and movement on the shaft smooth. The thrust bearing though was notchy so this is the only thing I can think of that could cause it not to engage, however by the time the pinion hits the thrust bearing it is in theory already fully meshed with the ring gear.

 

The pressed on gear starter clutch has some subtle differences. The spag clutch is a little narrower and the thrust bearing has a bevelled face at the shaft bush end. This thrust bearing can be moved back against the bendix return spring as well exposing a stop circlip on the shaft.

 

This is apparently the first failure of the pressed on gear they have had. I hope it is the last.

[Bluboyz]

IIRG the Jabiru starter motor’s original overrunning clutch assembly was a Honda 31207-ZE3-003 Clutch Over Running GX390 available from Honda small engine stores, Honda marine stores, and the internet.. Replaced one, a few years ago, at around 500+ hours in a J430.

[Bluboyz]

Sprag clutch failure, pinion shaft spline meshed to main drive cog, starter motor spinning down to stop audible after button released, virtually no prop movement.. (edit time expired)

[kgwilson]

Installed the new clutch & flew yesterday. It is virtually the same as the original with the main drive gear fitted on the shaft via a spline so the press fitted versions were obviously not successful. The only noticeable difference is the main drive gear is slab sided and there is no shim washer between the gear and motor bushing. The original was indeed a Honda confirmed by Jabiru but now are manufactured in China specifically for Jabiru.

[facthunter]

That type of starter engagement is not kind to flywheel bolts. Better to have the gear engaged before the motor is energised. This can only be done by a solenoid or a pull cable . Nev

[kgwilson]

Jabiru mandates flywheel bolt replacement at 500 hours I imagine partly due to stresses induced by the starting mechanism.

[facthunter]

The sandwiching effect is what takes the drive load and I'm not convinced with all the oil around you can successfully rely on the assembly doing that as well as when the whole engine is being put together originally. Nev

[onetrack]

You need to figure out a soft-start arrangement for the starter. Leece-Neville are producing new 12V and 24V starters for truck and industrial diesels that contain an inbuilt soft-starter.

There must be some smart electronics whizz who can design up an electronic "black box" that feeds in the electric current on a "current ramp-up" basis, to prevent the bang you get now, with full current supply upon starter initiation.

[facthunter]

The inertial throw in works on the starter commencing to rotate quickly. Do it softly and it doesn't move. There's a light spring trying to keep it out of engagement when not used. Put the starter gear behind the prop and all OK. Looks crude but works. Nev

[440032]

Today, I hit 500 hours and nearly 15 years on my Jabiru engine 2200 #1583.

Thank you Jabiru Aircraft Australia.

[kgwilson]

The inertial throw in works on the starter commencing to rotate quickly. Do it softly and it doesn't move. There's a light spring trying to keep it out of engagement when not used. Put the starter gear behind the prop and all OK. Looks crude but works. Nev

There will still be a sandwich effect load on the ring gear bolts that connect it to the crankshaft or prop flange so what is the difference?

[facthunter]

Much bigger diameter and area. You wouldn't use the prop studs as you can't tighten them enough. You could extend them through the flange or between the others on the other side. Also no oil about. Oil between the faces makes it un likely to not move more easily. Once it starts to move it's all over. I would be loctiting the cleaned faces at assembly and that keeps the oil away. Also much easier to get at to check. It's unlikely to be a problem Nev

[Old Koreelah]

You need to figure out a soft-start arrangement for the starter...

I would like one, ‘coz when my engine is warm, my lithium battery turns it violently.

 

I’ve read of an old Rolls Royce being started by spark alone.

I suspect you could start an engine without cranking motor, via smart electronics that sense piston position and combine fuel injection and retarded spark.

Edited June 6, 2020 by Old Koreelah

[Geoff_H]

The goggomobile used the generator starter motor, the one device for starting the engine. The engine was 2stroke. 4forward gears, 4reverse gears. For reverse start the engine in reverse. Gas turbines for power generation use the generator as a motor, when up to a speed where combustion can continue, turn off the motor, run the turbine up to speed and connect the generator.

Modern car engines have big generators to supply the electrical load, I wonder if these could be used to start an engine, maybe just push the engine to a position where spark ignition could start the engine.

[Bruce Tuncks]

Those flywheel bolts: It seems to me that while the bolts should be retained with nordlock washers, there should be loctite between the mating faces.

But this is not in the manuals...

[Bruce Tuncks]

So I agree with Nev.