Beat me to it... and much more effectively. Challenging Ross on ECU's?? Billski on re-drives??Pfarber- do you have the slightest comprehension of who you are so casually dismissing? Ross has overcome all of the mechanical and systems integration issues that you are just now starting to fumble around in the dark with. Auto conversion, Cooling, TV, redrives, and yes, ECU control. He's one of the few who have actually accomplished the process and now has a practical airplane. This, in an addition to manufacturing ECU's and EFI integration hardware for the past several decades.
Considering he is THE auto conversion authority on this forum, do you think it wise to try "take him to school"?
Way high. 23 years in automatic tranny design, and we ran as high as 97% with a significant oil pump and open clutch drag on half the clutches...95% with a cool running gear oil filled gearbox or 98% with belts is a conservative guess. So you lose 7 to 15 hp there.My statement " I suspect a minimum of 50 hp and probably a lot more than that will be used to drive the reduction drive." should have said "support" the reduction drive. As I said at the beginning of the post there are other things which have a cumulative affect requiring HP to offset their effect.Additional weight must also be offset by additional power, and running the engine at elevated rpms will generate more heat and friction within the reciprocating and revolving parts. Also the water pump , alternator, oil pump,will be turning higher rpms than they would at 2700 rpms, and it takes some power to offset that. More cycles of the pushrods and rocker arms per minute absorb power. Its a cumulative estimate
rather than a direct gear loss estimate....but it was a SWAG type of estimate based on a 10% rule of thumb with additions. Since we don't know the actual construction of the Redrive there is no way to have any really accurate number. Maybe TxFlyguy can provide some factory info on actual tests. One thing for sure is that it takes more power to use a redrive than a direct drive setup and there is less chance for harmonic issues. I just believe that if the amount of usable HP is available in the same engine type without using a redrive, to me thats a better solution. If the direct drive can't make the power, such as in a racing application, then reduction is warranted.
Way high. 23 years in automatic tranny design, and we ran as high as 97% with a significant oil pump and open clutch drag on half the clutches...95% with a cool running gear oil filled gearbox or 98% with belts is a conservative guess. So you lose 7 to 15 hp there.
I don't think we can accurately define how many HP TxFlyGuy's reduction drive will absorb since we know nothing about the actual design of the unit. Type of bearings used and gear size will affect the actual losses. TFG mentioned earlier that his gearbox is a larger and heavier unit than what was originally going to be used so it could withstand the Torque/HP of the LS3. It seems logical that this gearbox will absorb more HP to operate than the lighter duty unit. TFG said 380 HP @ 4500 rpms The Dyno chart below shows that an LS3 should produce 400 HP at 4500 RPMs. Since we should always plan for "worst case", 5% loss is 20 Hp.
As to extra power to haul the extra weight. 50 pounds of extra lift will cost you, what 6 pounds of extra induced drag? At 300 ft/sec, that is 3.27 hp.
Actually I think its closer to 400 than 300. I get 366. So lets just round it off at 4 HP.
So now you are losing 18 hp when running 300.
I'm at 24 HP.
Now to the accessories with the redrive. The stock pulley ratios are designed to get positive charge at 600 engine rpm and positive continuous cooling at high torque and 2000 rpm. Turning a prop at 600 rpm probably too low, but that is 1500 engine rpm. And turning a prop will only make much torque and this much cooling need in the upper 80% of whatever your operational max is. Alternator consumes power with square of its rpm, water pump with cube... accesory speed has a realLy big effect... You can run either bigger accessory pulleys or smaller crank pulleys or a little of both. Betcha there are go fast parts that are well proven for LS that do exactly this. So your added losses at the accessories might be true if you are not smart. Be smart though, and it can be zero.
Not really any actual numbers here but by my calculation I need to come up with an additional 26 HP to substantiate my 50 HP statement. Take way too much work to try to rationalize all the additional power losses due to the difference in internal friction increases due to higher rpms. Things like higher oil flow requirements to support the drive unit and the weight of components to route and cool the oil. Probably not needed on direct drive. Also, the mass and weight of the much larger 4 blade propellor compared to a smaller prop on a direct drive at higher rpm. Not suggesting a small two blade prop be used on the warbird, but its definitely something that most builders don't need, so again weight,mass,and resistance that can be eliminated with more common conversions. I do think that there is no way to make the accessory drives operate with zero loss though. Don't think any builder wants to use an electric water pump. From my experience, alternators seem to consume more power in operation than water pumps.
Can the truck crank carry the prop gyroscopic moments? Good thing to check... might need a separate prop shaft with some weight anyway.
As I mentioned in my reply to Ross, my personal opinion is that simply bolting an extension onto a crankshaft has been proven to work in some cases but I don't feel its a good way to do it. I would only feel safe with a direct drive design that had additional support for the direct drive. Corvairs have solved the problem with a supportive 5th bearing and examples similiar to Steve Wittmans design seem to work efficiently and reliably. So I think we are on the same page as far as not putting the gyroscopic forces directly on the main bearing and crankshaft.
Last part is these engines that are big enough to run direct are going to be heavier than the smaller engine that does it all with a redrive.
I don't think there is one answer that is always correct and each conversion must be weighed (pun intended) on its own merits. There are many factors to be considered in any conversion. Its not just about weight or HP. You have to consider that elevated rpms have negative aspects other than the consideration of piston speed. Heat production at higher rpms increases and requires additional means to dissapate it. Noise levels are higher. Component wear in the valve train and bearing surfaces increases, and engine life decreases.An engine must produce more than the desired HP output and burn additional fuel to do so. You must carry the additional fuel or fly shorter flights. You must bear the expense $$$ of the reduction drive which in larger engines is significant enough to kill the whole project for many people. The point here is that its not just a simple decision that one choice...or the other is always best. It depends on the builders resources and whats important to them. I had a Geschwender redrive and when I weighed it, it was 80 lbs. Others may or may not be lighter. There always seems to be questionable info about the weight of redrives. The cost of a redrive is a significant consideration in all conversions.
Redrive s have drawbacks, but efficiency ain't necessarily one of em.
Redrives always introduce additional cost/weight/reliability/and additional harmonic considerations into conversions at some cost to efficiency. How much cost to efficiency is debateable but there certainly are successful reduction drive conversions flying efficiently out there. I truly enjoy seeing and hearing any successful conversion . The sound of the raw exhaust is music to my ears.
I would like to say that my 50HP estimate is probably too high, but I think builders should consider all the issues that arise when running an engine at high rpms. I think there is room for both direct and reduction drives in the homebuilt world, and appreciate the inputs from wsimso1,Ross, TFG, and some of the others on this thread.
Pfarber. You came onto HBA with guns blazing, insulting each person in turn, who are professionally experienced in what you were posting about- TV, redrives, engines and now EFI. You do nothing to contribute to useful discussion, information or increasing knowledge here for other folks. Your tone is abrasive and unfriendly. Your posts show you have much to learn about all these topics. I wish you the best of luck IF you ever actually build anything and fly it, which I doubt will actually happen.
I am again thankful for the Ignore feature here on HBA...
I'm not burning bridges, I'm dropping dead weight.Beat me to it... and much more effectively. Challenging Ross on ECU's?? Billski on re-drives??
Judging by his response to your last post I submit that further efforts, should you choose, are for the sake of comedy. Else, a waste of bandwith.
I and others are free to post as desired in keeping with forum rules of conduct. This forum is for the benefit of of it's members in aggregate and, hopefully, corrections to misinformation will continue... including threads initiated by you. As to the veracity of your posted information, I defer to other knowledgeable sources here with demonstrable credibility.Please don't post in any thread I start. Thank you.
Hi Narfi, my post was supposed to be a joke; any time you ask a work crew when they can do a job, they invariably say 'Tuesday'. What can I say? Humor via the interwebs is hard.Maybe I misunderstood what was being posted, but I thought it was planned to fly a couple weeks ago,
That, by far is one of the best-sounding aircraft we have heard to date. There is nothing that can compare to a cross-planed small block Chevy. Well done!!One of our customers built this plane and just got it running recently:
We'll be following this more in the future.
That's a beautiful installation of the LS3 engine. The PSRU unit looks very nice also. Is that a purchased PSRU product, or a custom engineered and built PSRU solution for this particular plane and engine?One of our customers built this plane and just got it running recently:
We'll be following this more in the future.