danny_galaga

Love it! A story to tell 😊 In my case I thought I knew everything about aircraft. I didn't. I didn't understand that in most regular aircraft, the elevator needs to produce a little bit of negative lift in level flight. I actually added a positive angle on it. Just that one thing probably cost me several metres at least, and probably first prize. I came third. The flight itself was a total blackout for me, didn't remember it at all! Basically one moment on standing on the edge. The next I'm swimming to shore. Probably doesn't help that I'm not good with heights 😄

I can smell the ether just looking at it 😊

Man, just chuck a four barrel on it and wear the slight reduction in power 😊 On a serious note, I'm not quite getting what happened with the computer. Do those tuning sensors run though the computer? Or is it a typo and they meant to say those sensors were on the same circuit as the computer? Whatever the computer normally draws, it would still be drawing so I'm not quite following. And yes, WTactualF regarding taking off anyway. They were testing for power. But why bother if you're just going to ignore the result!

I rather like this little engine, designed from the ground up for aircraft. For their own aircraft as it happens. Listen to that cute chug in the last video clip ☺️ Built to rev at 'airplane' revs, it tops out at 3000. Only thing is it seems to not be dual ignition, but I could be wrong. https://spiriteng.com/spirit-v2-engine/ This is the plane it's designed for. What a lil beauty 😍 https://aopa.org/news-and-media/all-news/2025/july/31/a-neat-little-package

Yes, Cox have the glow plug built into the head. There is a diesel conversion for 049 but it's not very good. In the case of the 010 (0.15cc!) a regular glow plug would be nearly as big as the piston 😄

Do the guys designing redrives not know all that you know? I'm being serious. In these discussions, some guys here have concerns about the engine design (for instance, the crank bearings not being built for the types of loads an airplane puts on them), others say it's mostly peripheral things that let them down, like redrives. I seriously feel if that's the case (and I don't know if it is, I haven't looked at failure rates) then that should be something SOMEONE must be capable of engineering properly. Ostensibly, the engine it's connected to is way more complicated. There seem to be some big players saying they've got it sorted. If they have, they should make that a HUGE selling point and offer their design to suit all the most popular conversations. Their GOOD product should crowd out inferior products in the market. What is for sure in my mind, is that along with most of these engines being single ignition only, you have three distinct areas (engine design, redrive design, single ignition ) that aren't 100% 'aero' that allow for a higher chance of failure than an actual aero engine.

Bushcat too, and possibly the widest cabin in the ultralight category..

Thank you so much for this ☺️

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.