DR-1 (Sands): Builders Group

[worldcrusier]

A gentleman by the name of Ron Bloomquist built a DR1 with an AI-14, a close cousin and his comments indicated a good flying aircraft. His weight and balance came out at 30% MAC (Mean aerodynamic chord at 11.5" aft of the leading edge of the middle wing), very close to the original. By the way, I have heard that he was well along in building a Gotha. The M-14D variant does not have a (very heavy) gear reduction which helps the weight issue considerably.

[Belli]

Originally Posted by franzkait

OK. look how mutch a 1 cylinder shake . More cylinders les vibration. A 4 cylinder car engine shakes a lot but you do not realy feel it becurse the engine is in a heavy steel construction on 4 big weels. Radials have a special problem. Only the master rod cylinder has a good timing. All cylinders at the left side have 10 to 20 degrees wrong timing for spark and valve.If the left side cylinders have 10 to 20 degrees bevor TDC
the right side cylinders have have 10 to 20 degrees after TDC. So not 2 cylinders have the same timing. Engines like the Oberursel do not have this problem . Oberursel have a different con rod system.

This is really not true, I have done some investigation, including modelling and testing on a PC the timing issues with a seven cylinder, with even crank pin spacing the maximum error in the timing was 7 degrees, (on only 2 cylinders and less than 3 degrees on the others!) by adjusting the positions of the crankpins, you get even firing. A radial can be balanced almost perfectly as all the pistons and conrods, crankshaft and counterbalance weights are in one plane.

What cases most of the vibration in a single cylinder is the 'torque ripple', i.e. every time it fires it tries to accelerate the load quickly, with 2 cylinders this ripple is halved, with four etc. When you have 7 cylinders it is as smooth as a babies bottom! An inline four has little vibration as you have 2 cylinders going up when two are going down and the counterbalance weights are all balanced, (balance a 4 cyl. crank before assembling the engine) What cause the vibration here is the the maximum accelerations are around 75 deg. of crank rotation and not 90 dag. (close but not quite)

Greg

[jumpinjan]

Belli,
In this chart, they refer to it as "Q", the ratio of max torque/mean torque. This is the smoothness that you are referring to:

Then there are the balancing issues: Primary, Secondary and rocking moments or couples.

Then there are the unbalanced piston accelerations with respect to crank angle that you mention:

[franzkait]

for example 450 hp Pratt and Witny has even krank pin spacing , becorse there is not
enought space at the master rod to move the pins. Siemens SH14 7 cylinder still the same problem one cylinder is olways to hot.BMW 5 cylinder ,enought space to move the pins but still the same problem, becorse the master rod center makes a circel all ather con rods make a elipse.Make a drawing in your computer and put all togeter. The master rod circel and all the elipses, if you muve the elipses to far away you get more vibration. No engine is balanced 100 %. single cylinders have most time 50 %. More cylinder engines les than 50 %. My company did a big research abaut this vibration maybe 20 jears ago and we gave up with radials. Today we still have this problem
with same engines for the US army becorse we can not balance them 100 %. I am glaad to see there are people like you with engine knowledge.

how can the weight and balance be good if you look at the weight from a m14 to a Oberursel ? 95 % from all the Dr1 and D VII are tailheavy,becorse wrong tubing. So with a tailheavy Dr1 the balance is OK but the aircraft is to heavy. Do you know how heavy a original Dr1 is ? Orangos Dr1 is nearly double and F. Raiders Dr1 was not much better.It flys like a stone. To high landing speed.

Originally Posted by franzkait

guns and ammo, are in the center of gravity, but the engine is in front. It is not possible to use a m14 in a Dr1. Orango in LA has a 220 Conti in his Dr1 ask him how his aircraft flys.

M14D
This is completely incorrect, with the air compressor removed, and plenum removed or replaced, the engine is lighter and more powerful than the Clerget Jacobs himself perferred. If the engine power is governed to 1700 rpm it willl drive a full size prop, nothing else will. I speak from first hand experience, the engine is the best suited engine for such use. If Arranga's Cont 220 rattels and shakes, its because the engine and prop are improperly installed. The CG with engine, Oil and Gas on one end and a 200 lbs pilot on the other, is right on. The arcraft flys like a dream not a stone. It will drop like a stone but that is because of High Lift / High Drag (wings x 3) not because of the radial engine.

[franzkait]

How heavy is the clerget, and how heavy is the m14 ?

[Belli]

I suppose I should mention that the work I did was for a 7 cyl HCI engine for which I had purchased the plans, I say this as this topic creeps in every now and again. In my opinion the HCI is not suitable for the DR1 or anything else for that matter. I say this as the plans are terrible, one of the members on the CI group has redrawn the plans for CI and I hope that now they are much improved. As far as I know only one HCI has actually flown and that is the original 5 cel by it's designer. Rotec on the other hand built (if memory serves me correctly) about 5 prototypes and had around 500hrs running time before they built a production example. Sadly their engine is too small for a DR1 (I think it was a big texan who said"Ain't no substitute for cubic inches!"). Their engine is a very fine piece of work and they now have examples that have reached 1000hrs of running time.

Jan, very nice book you have there! A little more technical than I was going to go but very interesting. The rocking motion from the master rod is obliviated on the Clerget and the Gnome (I think) by each piston having it's own rod and using slipper pads on the crank, all held in place with a retainer ring. This is difficult to make but shows the tremendous skill those craftsmen from then had!

Greg

[Jim Bruton]

i am glad we have so many smart people here!

Belli (good to see you again!) - Rotec is looking for some initial purchasers for a larger 9 cyl 150hp- weight looks to be good too. If you and JumpinJan, DarkAngerl and Frankkait could look at it and render an opinion, it would be great to compare it to the M-14D, that would be great.

It is the likes of your recent postings that makes this forum a wonderful resource for us all. Thank You.

i am glad we have so many smart people here!

Belli (good to see you again!) - Rotec is looking for some initial purchasers for a larger 9 cyl 150hp- weight looks to be good too. If you and JumpinJan, WorldCruiser, DarkAngel and Franzkait could look at it and render an opinion, it would be great to compare it to the M-14D, that would be great.

It is the likes of your recent postings that makes this forum a wonderful resource for us all. Thank You.

The next time you sit down and ponder your sage reply, or are out in your hangar working on your DR-1 (or D-VII, in Achim's case), tune into the past to create the right ambience.

http://www.dismuke.org/Acoustic/index.html

4 Real Media streaming volumes of turn-of-the-century music. It's perfect for setting the mood!

[franzkait]

Greg, Gnome and Clerget have the standard con rod problem. Only Le Rhone and Oberursel have a different construction.my friend had a hci ,we did look at it and send it back. This is not an engine.And about cubic inches was it not H. Ford ?

[Maxim08]

Interesting dialogue regarding radials.
Regarding the M14, does anyone know where a hub for a wooden propellor can be purchased? Exhaust collector ring?
You have to just love the Aerodrome's forums!
Maxim08