danny_galaga

Phew! That was a lot of work, not even going TRY to look for the stator or rotor. You guys can do some research there 😄

Does anyone happen to know what other machines the starter and alternator appear on? I forgot to have a close look at the starter while I had the engine out, but I'm pretty confident it's a Denso. That makes sense since they also use a Denso solenoid (it does not necessarily follow, but as a manufacturer, if you've decided a companies starter motor is of high enough quality for you, then their solenoids should be too so why not stick to one supplier). Likewise, there seems to be a good chance the alternator is a Denso too. If not, following my logic, since the reg/rec is Ducati (which is probably Magnetti Marelli) then maybe so too is the alternator. That makes me sad, because if it's Magnetti Marelli, they kinda blow 😄 I have been having a bit of a look around while I compose this, and so far I have found these which are specifically for the 912: https://ecclestonaviation.co.uk/product/889751-electric-starter-set/?v=79cba1185463 (Rotax OEM 500 squids, plus freight) https://www.aircraftspruce.com/catalog/eppages/skytecRX12.php (improved aftermarket. 700-900 USD, plus freight. ) So going with my hunch, I started looking at pics of Denso motorcycle starters. Those superfluous lugs are a clue they normally bolt to a crankcase) I hit on the BMW F650 starter. It will need further investigation, my friend has a BMW F650. I can have a squizz, but not sure if I will have enough access. It certainly makes sense, since the F650 is also a Rotax engine. Single cylinder, so it would need ROUGHLY the same amount of force to spin as the 912. As well, someone else here pointed out that the F650 radiator cap is the same. What this is adding up to is that Rotax, naturally enough utilise what they are already getting for other engines they make. Of course the F650 has been around a while, so there may be a few iterations of the engine, which could include the starter. So even if it is the F650, we need to determine what years it used the same starter (if of course it is the same) The below link is for an AFTERMARKET F650 starter. Before anyone jumps the gun, I'm showing this link because it has quite a few pics from different angles. It is my preference to buy the same genuine part that Rotax buys, but paying the automotive price. I probably wouldn't get a cheap aftermarket starter. https://www.stein-dinse.biz/product_info.php?language=en&products_id=524427#prettyPhoto Too see exactly the same starter, it's useful to look for genuine second hand ones on ebay: https://www.ebay.com.au/sch/i.html?_from=R40&_nkw=bmw+f650+starter&_sacat=0&LH_PrefLoc=2&Brand=BMW&rt=nc&Brand%20Type=Genuine%20OEM&_dcat=177959 Particularly this listing https://www.ebay.com.au/itm/394431030976?hash=item5bd5ebe6c0:g:jbIAAOSwnQFjzr7C&amdata=enc%3AAQAHAAAA4BBbngib0YSE%2B6CMmjsCmTpUvXc9UZlt%2FfgQCtHur%2FN9tqAkwgwYcHrHWpcLICJlLUbPp3XbvdKtGA8KIW8R6raYzZcfQYI0gQP49M%2BQY7usc%2BqH%2BZgmY0sZwBeQTl%2BNZc0ab28Ev9pQvqeWGiUBDs7neO3lXe04bVr5ghxLIJleIFF8myKupAhmW1pZ09HT0OJTyX8IxFAibhoV%2BbPQavFTrJVmbVjI%2FPEtKbpSloRToz3CqwbwFicn6kkY7jWDj8A7psox9wg3rixECg3cM6Dl8EyZMoU3uWE%2BNtcoEv0E|tkp%3ABk9SR9K2rIXtYQ Of note, they clearly show the Denso part number ( 428000-5630 . Also 294 359 ) which is useful, should this turn out to be the correct starter. Again, gun jumpers, please I'm not intending to fit a second hand one unless I knew where it had been (only from a known 912 engine, not from a motorbike thats probably been submerged in rivers a number of times in its life 😄 ) If I'm reading the listing correctly, it's for models from 2006-2012. Italian listing, so not sure how well they translated it. They could mean only 2006 and only 2012, but that seems unlikely. Note that the Aircraft Spruce link also has some handy drawings with dimensions. Note that I'm attaching the pics from that ebay listing for posterity since ebay listings disappear after a while. The last pic (the clean, silvery one!) is of the genuine starter, for comparison from Ecclestones site. I am specifically only looking at the late model starter, as I believe the Black starter wasn't as powerful and should be upgraded anyway. NOTE NOTE NOTE NOTE!!!! I'm NOT saying this is definitely the same starter, but it's looking plausible. Something as simple as the wrong number of teeth on the armature could blow this out of the water (This starter has 9 teeth). Does anyone know anything else?

oh, i can see in the manual it is Setrab, same as the oil coolers. Setrab have agents in australia. I'll see if i can find a part number in the picture, otherwise i will still have to have a physical look.

I've been having fun taking note of alternative spare parts for my build. I will try and see what brand my radiator is next im at the hangar. Bushcat roughly similar specs to the Savannah.

I got a tablet JUST for flying. So I've only installed a nav app, and the build manual for my aircraft. I actually deleted some of the preinstalled apps as soon as I bought it just to keep it 'light'. I just filled in my application. fairly straight forward, but I always worry I forgot to cross an I or dot a T 😄

A bit of a crossover of my two hobbies. Long read, but very interesting 🙂 https://www.kotaku.com.au/2023/03/the-racing-game-that-changed-everything-was-built-on-lockheed-martin-technology/

https://bydanjohnson.com/fantasy-or-fantastic-futuristic-retro-junkers-introduces-distinctive-a50-junior/

Received my solenoid from the kart shop ok. I was going to buy one from Ecclestone aviation in the UK where I bought my Rotax fuel pump from but I forgot. Hence my mad scramble to find something in Australia 😄

I'm way over the hump now with my project and I definitely wouldn't have kept it as long as this guy, but a few of us have been there https://www.kitplanes.com/stalled/

Looks like you've avoided the RO-tax 😄

Agreed. I've seen it, having been an auto electrician, but it's not common. But what I'm driving at I guess is you increase the risk of it happening if you get a cheap solenoid. The contacts might not be as good a grade of alloy, or not very well aligned etc. So the original thrust of this thread was to find a reputable solenoid brand I could go with that is available in Australia. The mercruiser one was mentioned, but hard to know if I'm getting the real deal or not. But everyone can stop looking, because I've discovered a popular Rotax engine that uses the same Denso solenoid 🙂 https://www.rotax.com.au/shop/item/starter-relay-evo Which you can get from Go kart shops etc. My journey is done, and I'm also fitting a starter indicator light as well thanks to this thread. Thanks guys!

I think I've covered all that in previous posts. If engine continues running with solenoid fused, starter destroys itself through centrifugal force because the starter will remain engaged with the engine. Ratio of pinion to ring gear is easily 20:1 so even if the engine is only running at 1000rpm, the starter is spinning at 20,000rpm! If you stop the engine, then starter keeps spinning the engine over until battery goes flat, or starter melts down. As you alluded to before, starters don't like cranking for long..they get hot really quickly. If it has field windings, the insulation burns up causing shorts . And whatever type, the armature windings can also short out if very hot. The brush tags, if soldered can melt off. If the armature has soldered commutator segments, those can also melt. Molten solder is a saving grace in this case because everything becomes open circuit very quickly. The only way the starter would keep spinning for any length of time is if the pinion clutch failed, or didn't engage the ring gear. Then the starter would spin quite happily for ages. Although that would give you plenty of time to disconnect the battery 🙂

Agreed. But it won't be long before either the battery is flat or starter has melted down if the solenoid is fused. The voltage will drop extremely rapidly once it's been cranking for a while. This is because at rest a starter has virtually no resistance. When it is spinning it produces back emf. So at the instant of start, it might draw 500 amps, and within a fraction of a second, it is drawing only 100 amps because it is spinning. But say it gets down to maybe 8 volts. Now there isn't enough voltage to spin the starter, or at best very slowly.so it's virtually presenting as a dead short again to the battery. Now instead of only 100 amps, it's drawing 300 amps. At 8 volts it's discharging at 3 times the rate it was at 12 volts! The figures are just ball park to illustrate, but you get the drift. I'm not saying that's a great thing to happen, just pointing out all things being equal your battery will be quite flat quickly in that scenario, or the starter will burn out, going open circuit. I'm in two minds about adding a battery isolator. Yes, it could be safer but I'm also adding more and more weight and complexity. A ballistic chute thingy would make my plane safer too. Where does it all stop? But you have sold me on the warning light 🙂

I should add that a light on it's own isn't going to save your starter motor. You will need a battery isolator as well. I haven't got a battery isolator in my plane, might add one later. But the warning light will tell me the contacts are fused and best not to take off. All I can do at that point is shut off the fuel. Motor will stop, and starter will keep cranking till the battery goes flat or it burns out 😃

All you need to do is run one wire out to the starter side of the solenoid, and the other to negative bus. Then it only comes on when starter is cranking. If contacts stuck, light will stay on. If you wanted the reverse logic, you would have one wire on starter side, and the other on positive bus. Since a starter is almost a dead short at rest, in effect it is negative until you start it. So in that case the light would be on all the time except when starting, or contacts fused, or the internals of the motor are totally obliterated! Not really any point, I'm just showing off 😄

I think I might do that. But 'saving your life' might be dramatic. When a starter stays engaged, it gets spun up to higher revs than it's designed for. The armature windings start to move out, and at some point they, or the commutator segments fly out and arc out against the housing. As you would probably have seen, it's a big explodey mess inside the starter, no doubt. But once everything has fallen away the arcing stops pretty quickly. I take your point though. It would be yet another one of a large number of things that can rob your engine of power on take off. In this case, the loose chunks of copper etc inside the starter can cause extra drag on the engine. I'll pop in to Jaycar aeronautics and get a small panel mounted LED. I'll mount it where the key points at the starter position 🙂

I wish I could re edit posts more than 2 minutes later. I meant PLANE, not PARTNER 😅

Granted, I don't have enough experience to have had an engine failure (yet) but seems to me this issue the ideal situation to be landing the plane, rather than locking in the destruction of your partner by pulling the chute? https://www.avweb.com/aviation-news/285055/

I can keep it simpler by just using a good solenoid. What brand have you got? Is it the original Rotax part?

So what are you guys using for your Rotax or Jabiru starter motors? I just ordered some bits and pieces from overseas and thought I had included a Nippon Denso relay in the order. Looks like I forgot it, so if there's something thats proven amongst you guys I can get locally I'll do that. FYI, the Rotax part is a denso starter relay part number 182800-1950. It's less than half the price of a 'rotax' one. Pretty much anything around that size will do, including the knock off version. BUT.... if I use a $20 relay, and the contacts fuse together, it wasn't much of a savings if my starter motor goes nuclear 😄 I tried looking at other similar relays to get a feel for what's out there, but hard to tell without specific part numbers for each. I looked at relays for Honda CB900, BMW R1200, Polaris, Harley Davidson etc When I was a sparky, the solenoids we used for cars were fairly cheap, but blowing up a Rotax starter is a different ballgame to blowing up a Cortina starter 🤣

Simplest thing I can think of without mucking around with aerodynamic mods is to add an extra oil cooler inline with the existing one. Almost anywhere you mount it will add some extra cooling, even if on the firewall, unless of course it's right next to the exhaust 😄

https://bydanjohnson.com/mosaic-ready-powerplant-brp-rotax-surprises-sun-n-fun-with-a-powerful-new-announcement/

From this it implies Rotax themselves say 48 month shelf life https://www.rotax-owner.com/en/912-914-technical-questions/9671-912-fuel-pump-shelf-life?start=0

Yes, that has crossed my mind, that the rubber might perish just sitting there. I will investigate. My garage is cooler than my house, so heat shouldn't be an issue

Dunno if it helps, but at least some perspective from a different system - on the Bushcat, there is one small oil cooler above the radiator. Radiator is in much the same position as the CH701 as far as I can tell. Then another small oil cooler on top of the engine. The cowl ducts air straight to the cooler ( no hoses) and then straight out again, going over the windscreen.