Original Posted By: "skellytownflyer"
Subject: Re: Pietenpol-List: Engine questionAs this all sounds like a balancing act but then engine torque/rpm issues can be mitigated in some degree by matching up a propeller to that engine to determine the best combination to avoid exceeding the 92% of Mach speed at thepropeller tip at a maximum allowable Rpm. which at any luck will be at the max torque.I located this calculator to help make those calculations and plugging in a number of variables. _http://www.pponk.com/HTML%20PAGES/propcalc.html_ (http://www.pponk.com/HTML%20PAGES/propcalc.html) Like most things in this life, its not the end all but it certainly helps take much of the guess work out of the balancing act.JohnBTW does anyone have a resource for torque curve charts I want to check my engine options to see what they actually look like on the torque chartshttp://discover.aol.com/memed/aolcom30tour________________________________________________________________________________Subject: Pietenpol-List: battery life
Pietenpol-List: battery life
Original Posted By: "Gordon Bowen"
Well I bought new Gell cell battery last summer when I got my Tri-pacer annualed.YeaI know it's not a *iet-but is aircraft.I didn't fly much and it was deadby mid-winter.messed around and charged it back up and flew once or twice butstill had to jump it.but didn't take it back in time to get it replaced.nowI'm wondering if there are any tricks to getting a gel cell to accept a charge?I put a solar panel on the roof of the hangar in winter and kept it hooked upbut it won't maintain a charge.wondering if hitting it with a heavy chargermight wake it up-have tried slow charge and it seems to indicate enough voltageto cut back pretty quick but just won't hold.might crank it that day but a fewdays later-go back and it's dead.Gill put out some bad batteries I know.butI'm a tightwad and would'nt mind trying to get a little use out of it.still planningon starting cover on my GN-1 wings in about 6 weeks.RaymondRead this topic online here:http://forums.matronics.com/viewtopic.p ... __________
Well I bought new Gell cell battery last summer when I got my Tri-pacer annualed.YeaI know it's not a *iet-but is aircraft.I didn't fly much and it was deadby mid-winter.messed around and charged it back up and flew once or twice butstill had to jump it.but didn't take it back in time to get it replaced.nowI'm wondering if there are any tricks to getting a gel cell to accept a charge?I put a solar panel on the roof of the hangar in winter and kept it hooked upbut it won't maintain a charge.wondering if hitting it with a heavy chargermight wake it up-have tried slow charge and it seems to indicate enough voltageto cut back pretty quick but just won't hold.might crank it that day but a fewdays later-go back and it's dead.Gill put out some bad batteries I know.butI'm a tightwad and would'nt mind trying to get a little use out of it.still planningon starting cover on my GN-1 wings in about 6 weeks.RaymondRead this topic online here:http://forums.matronics.com/viewtopic.p ... __________
Re: Pietenpol-List: Engine question
Original Posted By: "LWATCDR"
I think the original thread on this discussion came regarding how to get by without the PRU using a car engine. Guess if one was building an engine for a tractor pull then having the long stroke for leverage on the crank good idea, or if building a NASCAR engine for routine 9000rpm (short stroke) would be great but we're talking aircraft. Engines like Lyco have very large bore and short stroke. Designed to run hours at a time for decades at 2500 rpm and at peak torque. Think the reason for big bore aircraft engines is first for durability and then improved breathing and lower frictional losses. Without PRU cannot run any car engine at RPM's needed to get to peak of torque curve, so what can you do to move the torque curve peak back to say 2700 rpm. Very few options. Don't think any car engine is designed for long durations of 4000 rpms even if you use a PRU. Could make cam changes to open small valves on small cylinders but in a big bore engines you already have larger and unshrouded valves away from the cylinder walls, no need to experiment with the cam. To adjust for poorer fuel/air burn in bigger bore you'd need two plugs per cylinder. The shorter stroke would mean less losses due to friction and less vibration. Subaru's seem to work for aircraft because they are 3.46" bore and 2.591" stroke, but still need two plugs and PRU to get the advertised 125hp. To get a car engine to work so it could run like a aircraft engine you have to consider: vibration (less with short stroke), and fuel/air vacuum pumping by the intake stroke of the cylinder (bigger valves on big bore engines). Someplace there's a website for a guy that builds VW engines for racing, he had made many changes in the cams and still came to the conclusion it all came down to bigger bore engines means better breathing and less frictional losses. I have a V-6 3.8L Ford engine with supercharger down at the hanger in FL, including motor mount, 225hp at 5200 rpm according to Ford. I'll donate it to anyone who wants to put it on their C-172 and do the flight testing with or without a PRU. Big fan of idea auto engines for aircraft, but haven't seen anything I'm willing to fly, yet.Gordon----- Original Message -----
I think the original thread on this discussion came regarding how to get by without the PRU using a car engine. Guess if one was building an engine for a tractor pull then having the long stroke for leverage on the crank good idea, or if building a NASCAR engine for routine 9000rpm (short stroke) would be great but we're talking aircraft. Engines like Lyco have very large bore and short stroke. Designed to run hours at a time for decades at 2500 rpm and at peak torque. Think the reason for big bore aircraft engines is first for durability and then improved breathing and lower frictional losses. Without PRU cannot run any car engine at RPM's needed to get to peak of torque curve, so what can you do to move the torque curve peak back to say 2700 rpm. Very few options. Don't think any car engine is designed for long durations of 4000 rpms even if you use a PRU. Could make cam changes to open small valves on small cylinders but in a big bore engines you already have larger and unshrouded valves away from the cylinder walls, no need to experiment with the cam. To adjust for poorer fuel/air burn in bigger bore you'd need two plugs per cylinder. The shorter stroke would mean less losses due to friction and less vibration. Subaru's seem to work for aircraft because they are 3.46" bore and 2.591" stroke, but still need two plugs and PRU to get the advertised 125hp. To get a car engine to work so it could run like a aircraft engine you have to consider: vibration (less with short stroke), and fuel/air vacuum pumping by the intake stroke of the cylinder (bigger valves on big bore engines). Someplace there's a website for a guy that builds VW engines for racing, he had made many changes in the cams and still came to the conclusion it all came down to bigger bore engines means better breathing and less frictional losses. I have a V-6 3.8L Ford engine with supercharger down at the hanger in FL, including motor mount, 225hp at 5200 rpm according to Ford. I'll donate it to anyone who wants to put it on their C-172 and do the flight testing with or without a PRU. Big fan of idea auto engines for aircraft, but haven't seen anything I'm willing to fly, yet.Gordon----- Original Message -----