Litespeed Posted December 15, 2015 Posted December 15, 2015 A leadwing is very smooth- but I would think quite heavy. Geoff has one I think. Maybe he can volunteer his motor for weigh in. 1
Geoff13 Posted December 15, 2015 Posted December 15, 2015 Or maybe not. The whole bike comes in at about 425kg or about 700 2up with 3 weeks of gear on board.
Marty_d Posted December 15, 2015 Posted December 15, 2015 There's a brief discussion about the motor on the Homebuiltairplanes site. Apparently there's been a couple of conversions done but yes it remains heavy.
kasper Posted December 15, 2015 Posted December 15, 2015 There's a brief discussion about the motor on the Homebuiltairplanes site. Apparently there's been a couple of conversions done but yes it remains heavy. It remains heavy compared to what? a specialist aicraft engine costing $15-25k? If it comes out at closer to $8-10k as an engine rebuild then conversion that gives me 65-80 real horses AND we already have airframe weights sufficient to carry it sign me up. We have to be realistic - the cost of aircraft engines is prohibitive ... always has been ... that's why there were SO many VW conversions thorugh the 1960-90's then along came people with heaps of cash that bought the line you have to have a specialist aero engine and now we are where we are. Frankly Mr Rotax has been taking the pi$$ on pricing for the past 20 years and by discontinuing the two strokes are forcing everyone into the 80+hp very expensive engine areas. By contrast Mr Jabiru has been more realistic on pricing ... but a volume bike/car engine that converts for aircraft use while heavier is going to have to be cheaper to have a chance ... but IF it is then thats OK in my book. My problem with people like http://flyeco.net/index.html is that the pricing of their 3cyl car conversions is the same or higher than Rotax ... will not compute
Marty_d Posted December 15, 2015 Posted December 15, 2015 It remains heavy compared to what? a specialist aicraft engine costing $15-25k? I agree, I don't particularly like the price of Rotax either. I read one post about the Goldwing conversion, the poster had seen an article in "Contact" magazine about one, he thought the weight quoted was 250lb +. That's around 114kg compared to the Rotax's 64kg - so 50kg heavier for around the same power output.
facthunter Posted December 16, 2015 Posted December 16, 2015 There's an alloy 3 cyl Ford turbo petrol that's powerful and has to be light. Out of a prang it's not going to be very expensive The redrive is the issue. but there are other like mounts and cooling plus oil cooler The jabiru is LIGHT and direct drive. Two important advantages before you go any further, but then it's aircooled and relatively cheap and a simple design. I prefer the six. Nev
Litespeed Posted December 16, 2015 Posted December 16, 2015 Those little Ford engines are very good from all accounts. Designed with Cosworth- they know a bit about engines. Bike engine wise- I would go the BMW twin, proven and popular in Europe. Not too heavy and not too expensive.
Marty_d Posted December 16, 2015 Posted December 16, 2015 Those little Ford engines are very good from all accounts.Designed with Cosworth- they know a bit about engines. Bike engine wise- I would go the BMW twin, proven and popular in Europe. Not too heavy and not too expensive. Talk to the guys in South Africa, they've had a bit of experience with these and the TakeOff redrive. Great motor and a redrive specifically engineered for them, and apparently they're still a lot of trouble to get working properly unless you're very good mechanically.
fly_tornado Posted December 16, 2015 Author Posted December 16, 2015 Aren't those SA guys using their own homebrew ECU? so good luck with that
Marty_d Posted December 16, 2015 Posted December 16, 2015 Aren't those SA guys using their own homebrew ECU? so good luck with that Some are, some used the TakeOff unit. Success with either is apparently patchy - some work well, some don't. The advice I got was "if you want to fiddle, go the BMW - if you don't, buy a Rotax." I was initially very keen to go an auto/motorbike conversion, but I know my limitations.
fly_tornado Posted December 16, 2015 Author Posted December 16, 2015 I've heard ppl on forums talking about mechanics who are struggling with concept of balancing carburetors on the rotax. 1
facthunter Posted December 16, 2015 Posted December 16, 2015 A largish capacity flat twin in a light airframe will tend to have a few shaking problems. The light flywheeled R100RS wasn't pleasant at idling and just above. All motors where the pistons stop at the same time have a problem of losing and reversing rotational inertia. (varying flywheel effect) They balance well enough otherwise except for cylinder offset which leaves a rocking couple hard to eliminate the effects of. The way it's mounted in a motorbikeTHAT doesn't matter much. Nev 1
kasper Posted December 16, 2015 Posted December 16, 2015 A largish capacity flat twin in a light airframe will tend to have a few shaking problems. The light flywheeled R100RS wasn't pleasant at idling and just above. All motors where the pistons stop at the same time have a problem of losing and reversing rotational inertia. (varying flywheel effect) They balance well enough otherwise except for cylinder offset which leaves a rocking couple hard to eliminate the effects of. The way it's mounted in a motorbikeTHAT doesn't matter much. Nev And most people forget that the original Rotax 912 was in fact a doubling of the Rotax flat twin into the flat 4 - the flat twin was unveiled but did not launch BECAUSE it wanted to shake the world to pieces whenever it was running ;-) 1
Marty_d Posted December 16, 2015 Posted December 16, 2015 I've seen a 701 with a converted Harley motor - I thought they were asking for trouble, Harleys convert 90% of their power into vibration... 2 3
facthunter Posted December 17, 2015 Posted December 17, 2015 Phil Irving was well aware of the "problem" I mentioned, He recommended an angle of 67 degrees, as optimal I believe but it would depend on conrod length. That might affect 3-4 degrees each way. 90 degree Vee Twins are fairly smooth and a vertical twin like the early triumphs used in the benson ? Gyros are not a lot different to a single, balance wise. Some Harleys use balancer shafts so their balance would be quite good, but that's extra weight. . When you get fairly big cylinders with not many of them and only firing every second turn (4 stroke) you are going to get pulses (torque) of some significance. Balancing ANY V twin uses the same process and concepts unless the pins are staggered. I've been doing them for years A Vee 4 with a 180 degree plane crank configuration might be the go for an aero engine, otherwise a two row 2 stroke six cyl radial has appeal. Nev
Marty_d Posted December 17, 2015 Posted December 17, 2015 I've had a couple of Honda VFR750F's and often thought they'd make a good aero engine. Bloody smooth, never had a problem with them. Around 104hp. Details from Wiki: The VFR750F models all used 748 cc 16-valve gear driven DOHC liquid-cooled 90° V4 engines with carburetor-based air/fuel induction; the bore/stroke remained the same for all 750 models at 70.0 x 48.6 mm (2.756 x 1.913 inches). The engine was made of cast aluminium alloy with the crankcase being divided horizontally, VFR750P and VFR750K models use slightly different crankcases with the lower casing being modified to allow for the gear position indicator in place of the neutral switch. On all the VFR750 models the gear drive for the cams was between the cylinders. Lubrication was via a wet sump with a chain-driven, dual-rotor oil pump; an oil (air) cooler was also fitted. The transmission was a 6-speed, with a constant-mesh, wet multi-plate clutch and chain drive to the rear wheel with the exception of the 5-speed VFR750P which had a spacer in place of one of the gears. The VFR750F uses a 180° crank, instead of the 360 degree crank used in the VF and VFR750R. In comparison to the VF750 almost every component had weight shaved off it, each con-rod lost 90g, rocker arms 6g, intake valve 0.5g, exhaust valves 1.5g, pistons 20g, piston rings 1.3g per set, valve springs 17g each. The V4 engine has proven itself highly reliable, with few known faults. The gear-driven camshaft system removed any lingering concerns about cam-chain maintenance, which had dogged the VF-series of Honda V4 engines. Valve adjustment on first-generation VFR750Fs was by screw and locknut, which changed in 1990 to shim-under-bucket, along with the valve-clearance inspection interval (to 16,000 miles). However, RC36 engines have been known to reach well over 50,000 miles without any need to adjust the valve clearances. Second- and third-generation VFR750Fs have notoriously suffered from failed regulators/rectifiers, likely caused by heat damage. Although Honda eventually re-designed the replacement part, such that failures of the new, finned regulator/rectifier are rare, some VFR750F owners carry spare regulator/rectifiers[citation needed]or even install small cooling fans to prevent reg/rec units from overheating. 2
facthunter Posted December 17, 2015 Posted December 17, 2015 Might be fine. The redrive and mounting them are the difficulty A set of gears to take a lot of torque aren't easy to engineer. For simplicity and cost I would favour a direct drive, but not rule out the red.gear. A bigger slow revving prop is able to be used then, but a longstroke slower revving motor can be built pretty lightweight and cheap. Making one from scratch is not impossible, but the powers may change the rules Pollution etc and you've been to the taxidermist. Nev
fly_tornado Posted December 17, 2015 Author Posted December 17, 2015 this is the thing about aviation engines, there ain't a lot to them. Even something as common as an O2 sensor is seen as being witchcraft. http://www.aopa.org/News-and-Video/All-News/2015/December/14/Indy-car-speed-with-Prius-fuel-consumption 1
Marty_d Posted December 17, 2015 Posted December 17, 2015 Bloody expensive witchcraft, one went on the car last year and it was $500+ for a replacement.
facthunter Posted December 17, 2015 Posted December 17, 2015 Having a single 02 sensor for a pile of cylinders isn't the full answer either. Getting the mixtures even is the most important factor as a starting point. You can turn a red hot exhaust valve into a sparkler with a lean mixture and what happens to the minute amount of oil film on the cylinder walls you rely on for lubrication, when there is an excess of oxygen. Every bit of it gets burned. Weld with an oxy torch and unless you have the exact flame at the tip, you will do a crook weld. Excess oxygen will damage hot parts. Nev
Old Koreelah Posted December 18, 2015 Posted December 18, 2015 Phil Irving was well aware of the "problem" I mentioned, He recommended an angle of 67 degrees... I used to read every instalment of Phil's "Rich Mixture" column in Rev Motorcycle news. Kept the lot for decades until the white ants found them... ...90 degree Vee Twins are fairly smooth... Aprilia use 60 degrees on their twins. I loved the smoothness (and sound) of my 90 degree Ducati but it had a down side; compared to my old parallel twins it was too smooth. Lady passenger had to yell at me to change into top gear. 1 1
facthunter Posted December 18, 2015 Posted December 18, 2015 I wooden have thought white ants would feel too good about eating Phils rich mixture. His rotten pipe would keep most things away. Do many here have any idea of how many brands of motorcycles were made in Australia.? Jennifer Byrne said one night on the ABC "everybody knows Australia NEVER made any motorbikes" Nev
mnewbery Posted December 18, 2015 Posted December 18, 2015 http://www.odd-bike.com/2014/07/hunwick-hallam-hunwick-harrop-aussie.html 1
facthunter Posted December 18, 2015 Posted December 18, 2015 There's about 100 bikes made before that at least. Check Australian motor bikes A to Z by R Saward Nev 1
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