danny_galaga

So what's sillier - Rotax knowing they have to try hard to make a safe gearbox, or all the car converting people (some with millions in their budgets) who don't seem to know you need to try really hard to make a safe product 😄

It's designed around that spring. So much so that there's anecdotes that taking the spring out makes it run rougher! A Cox engine compared to any other engine we are familiar with is like quantum mechanics compared to Newtonian physics- you just have to accept it works, without fully understanding why 😄 Pic is from the net BTW. However, THIS pic is mine. If I'm having trouble with an 049 (0.75cc) imagine what it'd be like running this 010 😲 . But then again, strangely enough, at this size they go back to rotary valve, notice the venturi and external fuel hose. It would probably be easier to start ☺️ I will never run it through. It's worth more as a collectors item in its box.

In which case, since only Rotax are seemingly able to build a reduction drive for aircraft engines, for safety's sake it would be best if all other punters desist.

Radial mount Cox 049s have a fuel tank attached to the back of the engine, from the factory. I'm pretty confident they are using the correct stuff ☺️. The only problem is variation in length, sometimes the end gets squashed

I'm hearing this a lot in these discussions - the engine is supposed to be fine, but the redrive is a weak point. Why the hell is it so? It's just a couple of pulleys or gears in/on a housing. It's not a freakin Saturn rocket engine. Try harder, car converty people!

The fuel hose has a roughly 2mm ID. I can't imagine any 20+ cc engine running on that size hose. Besides, there's no need to screw around with incorrect stuff when there's stuff available for model engines. 049 fuel tank is just not a great design. If the fuel hose is a tad long, the end gets blocked like mine did. It actually has a tiny spring inside to help stop it kinking. If the hose is a tad short you're seriously reducing your run time.

I think why not is adequately covered by the simple fact that for car manufacturer that makes millions of the same thing, the tiny profit to be made from bespoke aircraft engines is just not appealing. I'm actually quite amazed (and grateful) that Rotax make the 912. How many have they made? I think I heard somewhere in the range of 50,000. In the same kind of time period they made three times as many 650cc engines for BMW, and MILLIONS of snowmobile engines, without all the headaches that come with the aviation world.

Be that as it may, Rotax 912 is a very reliable engine. As is the texron range. Isn't this thread about automotive compared to aero? In this discussion, Rotax and texron are on the same side.

Point is, they didn't blow up getting there.

Yes, and they look the part. But seriously, Google how bulletproof the gsx 1100 was.

Damn, that's a LOT of trips to the shopping mall!

So while I'm in the camp of prefering engines designed from the get go for aircraft, still the idea is intriguing. Here's what I would do to start with for two different scenarios depending on aircraft size: For big boy planes first, I would look at many years worth of Paris to Dakar rallies. I'm sure there are many categories, not just standard and modified. In the categories of standard and slightly modified (whatever that might be called) which cars were the most reliable? Not including the support trucks, which had an open class of their own at one stage. I suspect an 11 litre DAF truck engine is a bit out of the airplane league 😄 Don't look only at what won, but what used the least spares, and what spares were needed. That there is your most reliable, bullet proof engine most akin to an aircraft engine. Will probably be over engineered in some places, and maybe a tad weaker in others, but to me would be your best bet. Talking of bullet proof, for ultralights, look no further than a late 80s Suzuki GSX1100. Around 120hp, air-cooled. Built in gear box sounds a hindrance at first thought. But you need a reduction box anyway. Pull out all the gears and lay shafts and just fit the minimal to get your prop right. The output shaft already is designed to take an absolute flogging from the chain drive. Maybe a short prop shaft and bobs your uncle! The only downside with my pick is these engines are now 30-40 years old, so careful reconditioning is key.

So about 50 hours per engine? My Rotax is good for 2000. And a number of them have gone to around 4000.

How many hours before overhaul on an F1 engine 🤔

Less power on takeoff and also no filter at a time when you most need it!

The idea is that the ice tends to form on the inside of the carby throat. If that's warmer then the ice doesn't form. There's no particular need to warm the air as such, just that on air cooled engines it's a pretty easy solution, with a side effect of having a useful alternate air inlet.

Depends what type. On mine, and many others, it's liquid heated. And only heating the inlet flange, not the air. It's permanently on. Since online the inlet flange is heated, it has virtually no effect on performance, but obviously it would probably take too long to work if you could turn it on and off

What I mean is, compared to my rotary valve 049 on the other plane, this one, with its ostensibly safer spring start has caused me more injuries 😄 049 fuel hose is way smaller diameter than chainsaw hose. As you can see, it's running now 🙂

Well, I took the lil model to the club today. It wasn't playing the game. The guys recommended 3 to 3 1/2 turns on the needle valve. I ended up flattening my battery and getting way more raps on the knuckles than I do without a spring start 😄 Went home and pulled the attached fuel tank apart because we all suspected something was not quite right. Crimped fuel pick up or missing reed valve etc. Sure enough the fuel pick up end was kinda squashed. I fixed it up and started it up at home. Running at 1 1/2 turns! A couple more tanks will see it settle in. VID_20260208_163601.mp4

One cell is just a smidge over 2V. 2.2V will actually do in the plug faster than leaving my 1.2V connected.

While it's been a while, it's not my first rodeo ☺️ Once started, the glow plug still glows, so I'm not sure how much life I'm saving. But it's prudent to be fairly quick to not flatten the battery. This was super important as a kid when I only had those huge 1.5v alkaline batteries.

So, continuing with scratch building stuff I could just buy, heres the other end of that clip. Made from some pen barrels, K & S tubing and a small bullet head nail. I don't want lots of paraphernalia or a giant flight box, so this keeps things about as simple as can be. The glow driver is USB charged and fits almost everything else. Now I can use it on Cox ☺️

Well spotted! I was googling for ohlssen with the ignition set up to emphasise it's 'olden dayness ' 😄 No idea why that came up instead 🤔

At the risk of sounding pedantic, because yes the odds are big, they are not 100 billion to one big. If there is an inherent design fault in the switch for instance, and they are from the same batch, chances are much higher. That is, if they have the same built in issue, there's a good chance they will wear out at roughly the same time. And I'm not suggesting they did this, but if one switch has been a bit iffy for a little while, and someone just holds it on takeoff just to be sure, you've allowed the other, very slightly better switch to 'catch up'. Again I don't have any experience with this sort of thing, but the odds of two switches failing at the same time are not quite as steep as you might first imagine.

Matthew followed me in his aeronca and took this in passing, my first air to air picture of my Bushcat 😊