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RE: Seidel 7-70 radial: Help me decide! - 2/12/2012 1:09 AM   
Mein Duff



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Status: offline 		Teus, Thanks for posting that fabulous engine...makes my mouth water just hearing that sound and crackle...just the way they should sound... Will check out his website, awesome machining.

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RE: Seidel 7-70 radial: Help me decide! - 2/12/2012 1:27 AM   
geezeraviation


 

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Status: offline 		I have been fortunate enough to be present during engine run up and testing of the VERY Originally built Fokker DR I replica at Olde Kingsbury Aerodrome in Kingsbury Texas. Its Le Rhone powered and the entire bunch of us that were present were up close and personal holding the aircraft down. The exhaust note is quite present as there is no manifold or header but what impressed me most was the extremely busy mechanical sound of the valve gear. Like a large room full of large sewing machines. A truly extrordinary sound when coupled with the whirring of the spinning cylinders. A magical experience for a WWI modeler.

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RE: Seidel 7-70 radial: Help me decide! - 2/12/2012 2:03 AM   
TFF


 

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Status: offline 		I wish I was closer to Olde Kingsbury; Steve Freeman is local and have talked with him about flying the Dr1.

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RE: Seidel 7-70 radial: Help me decide! - 2/12/2012 2:19 AM   
geezeraviation


 

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Status: offline 		Is Steve related to Roger? I know Rogers father was in California and passed away a couple of years ago or so. He was also into replicas and restoration and they had to go truck a bunch of stuff to Kingsbury. I put maiden on my 1/3 Nieuport at Kingsbury, its a two hour drive from my house. Its a great place to go hang out for a day and help work on old airplanes. They're redoing the Tommy right now along with a gaggle of other projects that always seem to be in progress. There will be a crew on the Tommy and guys working on the old ambulances and war era vehicles and some on the fire engine, the laser (they have a big one, I dont know how much power) is always busy as they do a lot of contract work with it as fund raising. Ive seen it burning neat pieces out of 3/8 steel, awesome.

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RE: Seidel 7-70 radial: Help me decide! - 2/12/2012 3:54 AM   
TFF


 

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Status: offline 		Steve is Rogers' brother. He has the PT-22 he flies down. I think Steve is a big fund infuser. From what I Know the Tommy was the fathers; been in the family a long time. They were friends with Frank Talman. Lots of good stories. Steve's hangar up here is the only one I know of that is perfectly equipped; every tool I can think of that I would want.

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RE: Seidel 7-70 radial: Help me decide! - 2/12/2012 1:09 PM   
geezeraviation


 

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Status: offline 		They have two Tommys, Thier dads needs a full restoration and the one they're freshening up right now is the one thats been flying at Kingsbury for umpteen years or twenty???

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RE: Seidel 7-70 radial: Help me decide! - 2/12/2012 3:00 PM   
Spuetz



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Status: offline 		Doc and the others...

as far as "mass production": may be not quite "mass", but I have been looking at replicaengines now for a number of years. I rememeber contacting them a couple of years ago because I, too, was dreaming of a Fokker E3, Dr1 or something similar, equipped with a scale Gnome ore Le Rhone. I even had come up with a "scale" way to introduce a throttle (which they don't have...): I was going to use a govenor as is used to keep the rpm of helicopters constant. I would have connected that govenor to an interrupter for the ignition. Much like they did back then: on final approach they would kill the ignition periodically, thus bringing the power down... neat idea?
may-be.

However, the problem is that their Gnome would turn a 24 x 10 at roughly 2,400 rpm which results in a propeller wind speed of 22mph! - waaaaayyy not enough power even for the lightest built E3... Hence I gave up. But what beautiful engines they are!
cheers, Martin

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RE: Seidel 7-70 radial: Help me decide! - 2/12/2012 3:29 PM   
abufletcher



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Status: offline 		Martin, I'm curious about the math. If a 24/10 is something like a scale size prop for a 1/4 scale EIII spinning at something like a scale speed, why would that not be sufficient for a scale EIII? Also how do you get to that number of 22mph? And really what does "propeller speed" mean anyway?


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RE: Seidel 7-70 radial: Help me decide! - 2/12/2012 3:56 PM   
geezeraviation


 

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Status: offline 		Yes if its going to turn that slow it needs to have pitch in the 20 to 24 range to provide enough speed for proper flight. Propeller speed is achieved by multiplying the pitch by the rpm which gives distance in inches per minute then multiply by 60 for distance per hour then divide by the number of inches in a mile to achieve miles per hour. Props arent 100% efficient though having as much as 20% slippage depending on some variables like temperature, humidity and altitude (its all lumped into altitude density) anyway actual speed is always less than the figures add up to.

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RE: Seidel 7-70 radial: Help me decide! - 2/13/2012 9:38 AM   
Spuetz



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Status: offline 		Don, good morning and greetings from ice cold Germany...
The answer is simple: because the density of the air and gravity is not 1/4 scale...

Just some musings around this:
Have you ever noticed that model ships don't produce a scale looking wake? However, if you put the ship in some special kind of oil (as they do in film making) that looks different... you probably also have noticed that scale models almost always have a problem with getting the scale of the propeller right. They are always too small. When you do get them right (gear box, electric outrunner, slow turning radial) they still turn too fast for scale.
Also: A model at 1/4th scale does not weigh 1/4th of the full size. Otherwise we'd be looking at 500 lbs or more per model...
All in all: when it comes to weight, power needed, air resistance and so on, scale is not a linear function, but has an exponential element to it...

Here is a little math:
I chose propeller thrust speed, because it is easy to calculate and gives me a rough idea.
How to calculate?
"Pitch" is the indication of "clean" forward travel per turn (clean meaning, if air was solid - like a thread in a nut)
So the prop theoretically travels forward 10 inches per turn
at 2400 turns per minute thats 24,000 inches per minute or 1,440,000 inches per hour.
1,440,000 inches are 22.73 miles.

at 5200 rpm that's 50 mph - much bettter!

as far as thrust is concerned: I have a thrust calculator (that I was too lazy to find, open and use in the last post ).
This tool gives me for a 24x10 prop, turning at 2,400 rpm a required power of only (!) 0.3 HP and a Thrust generated of 1.8 lbs.
At 5,200 rpm this changes drastically to 10 times the required power of now 3.02 HP and 18.1 Lbs of thrust generated!
Note: a (little more than) doubling of rpm requires 10 times the power! That's why the Seidel wouldn't pull the FW 190!
Another way of looking at this:
5200 rpm give 18 Lbs of thrust. 6540 rpm (not that much more, right?) give 36 lbs of thrust! DOUBLE!

Cheers, Martin



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RE: Seidel 7-70 radial: Help me decide! - 3/11/2012 12:13 AM   
radial1951


 

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Hi Martin

You raised an interesting point. Many people fall into the "SCALE" trap!! Perhaps an explanation may clarify...

If a full size plane, or any 3 Dimensional object, is e.g. 2000lb then a 1/4 scale model is NOT 1/4 of the mass of the full size. It will be the CUBE of the scale factor i.e.  4 cubed = 64 Therefore the mass will be 1/64th of 2000lb = 31.25lb  this assumes that EVERY component has the same material density and is exactly 1/4 of the SIZE in length, width and thickness. 

Typically, 1/4 scale models vary from the calculated mass either because the materials are usually less dense e.g. balsa vs spruce, aluminium vs steel, CF vs metal etc.  AND / OR, the sizes of frame members are often larger than true scale size as the chosen material may be too weak in very thin sections.

For a 2 Dimensional object, say WING AREA, it is the SQUARE of the scale factor which does the job i.e.  for 1/4 scale,  4 squared = 16  Therefore the wing area will be 1/16th of the full size plane's wing area.

So we have a 1/4 scale model with a wing area of 1/16th of the full size, supporting only 1/64th of the mass and therefore a much lower than "scale" wingloading. This very much works in our favour...

Regards RossG
radial1951
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quote:

ORIGINAL: Spuetz

Just some musings around this:

Also: A model at 1/4th scale does not weigh 1/4th of the full size. Otherwise we'd be looking at 500 lbs or more per model...

All in all: when it comes to weight, power needed, air resistance and so on, scale is not a linear function, but has an exponential element to it...

Cheers, Martin



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RE: Seidel 7-70 radial: Help me decide! - 4/28/2012 10:24 AM   
Teus



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quote:

ORIGINAL: Teus


Two 1/4 scales Gnome's are currently build and almost finished. One intend for a ''Brik'' (pusher version) and one for training on a Proctor Fokker E.III


First engine test runs



And if you can't build your own working replica engine, Achim Engels shows here how to build a wooden mock-up:

1:1 wooden Oberursel build

Starts at the bottom of page 12.

< Message edited by Teus -- 5/14/2012 8:06 PM >

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RE: Seidel 7-70 radial: Help me decide! - 4/28/2012 10:41 AM   
Spuetz



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Status: offline 		Hello Teus,

great! What rpm? What Prop?
Does it have a throttle? or just full power, as per original?

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RE: Seidel 7-70 radial: Help me decide! - 4/28/2012 10:56 AM   
Teus



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Status: offline 		I will try to find out Martin.

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RE: Seidel 7-70 radial: Help me decide! - 4/28/2012 11:18 AM   
abufletcher



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Status: offline 		Teus, the engine sounds AMAZING! Just wish I could SEE it! And Martin, thanks for explaining the calculations. I didn't respond back when you posted in February because I was traveling. But very useful information!

By the way, looking at the nifty "motor bicycle" that Achim is riding at the beginning of that thread reminded me of the bike that an old guy here sometime rides up to the flying field. He says he can get it up to about 50 kilometers per hour. That's faster that I'd want to be going on it!



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RE: Seidel 7-70 radial: Help me decide! - 4/28/2012 3:45 PM   
John Cole


 

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quote:

ORIGINAL: Teus


quote:

ORIGINAL: Teus


Two 1/4 scales Gnome's are currently build and almost finished. One intend for a ''Brik'' (pusher version) and one for training on a Proctor Fokker E.III


First engine test runs




And if you can't build your own working replica engine, Achim Engels shows here how to build a wooden mock-up:

1:1 wooden Oberursel build

Starts at the bottom of page 12.


DH-2, DH-2, DH-2 (chant in unison...)

John



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RE: Seidel 7-70 radial: Help me decide! - 4/28/2012 4:06 PM   
Spuetz



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Status: offline 		how about those?

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RE: Seidel 7-70 radial: Help me decide! - 4/28/2012 4:26 PM   
abufletcher



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RE: Seidel 7-70 radial: Help me decide! - 4/28/2012 4:58 PM   
Mein Duff



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Status: offline 		Just needs a set of wings and a tail to be complete

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RE: Seidel 7-70 radial: Help me decide! - 4/28/2012 5:13 PM   
Spuetz



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Status: offline 		and it would be interesting to lean into a turn - especially with the right one. What with the torque forces...

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RE: Seidel 7-70 radial: Help me decide! - 5/14/2012 8:08 PM   
Teus



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quote:

ORIGINAL: Spuetz

Hello Teus,

great! What rpm? What Prop?



Hi Martin,

Just heard that the engine runs approx. 3000 Rpm with a 26x18 prop!

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RE: Seidel 7-70 radial: Help me decide! - 5/14/2012 8:47 PM   
geezeraviation


 

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Status: offline 		That's a speed of 51mph at 100% efficiency. At 1/4 scale that should be enough to fly most models. Not much extra though.
Doc

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RE: Seidel 7-70 radial: Help me decide! - 8/25/2012 4:06 PM   
Pull Up Now!



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Status: offline 		Hello, I'm a nubie on this forum. Considering which radial to buy. It's maybe down to Evolution or ASP. WHICH IS BETTER? is Seidel now Evolution? Are parts available? Repair? Is the Evolution reliable? Any comments on ASP's reliability?

Thanks guys
Rick

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RE: Seidel 7-70 radial: Help me decide! - 8/25/2012 5:21 PM   
BobH


 

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Status: offline 		Evolution engines are sold by Horizon Hobby. Big supplier and big support (for our hobby). ASP engines are cheaper. I doubt that they are as reliable as the evolution engines. Nor are they as reliable as the Saito radials and the OS radial.

You can check the engine forums for better information.

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RE: Seidel 7-70 radial: Help me decide! - 8/30/2012 9:20 PM   
Mein Duff



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Status: offline 		From what I am hearing from people who actually have either of these engines..(the original Seidel or Evoloution I mean)...they are very happy with the performance so far of both engines. A recent conversation about them was that they run just great on 95% alcohol and only 5 % oil.

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