D Bronk

... Hi Jim .The Velocity Stack, was made long ,and it slips off, Just for the purposes ,you`ve mentioned .Haven`t had a chance to Fool with it yet,But, when I do ,I`ll just pop it off ,Rub the file on it, and shorten it ,bit ,by bit,and test..Didn`t cost much, to make that ,just a,few pennies,and some time..I`ll probably make a couple more Stacks,with different "FLARES" on top of each of them..Then once I find a Stack, that is a,"Keeper "I`ll just solder it to the Venturi..

..Fora #3, and ,#4, were in the mailbox today.They must have been, Stuck at Customs ,for a while..Maybe ,they thought these were parts,of a larger part, of a weapon, of "MASS Destruction".!!!![sm=48_48.gif][sm=what_smile.gif][sm=omg_smile.gif]

hogflyer

Watch out for DB – he’s coming out of the terrorist closet and will single handedly destroy the known world with 7 Fora .020’s.

D Bronk

...The World, has nothing to fear in me.All I want to do, is , RULE The UNIVERSE !!!!

D Bronk

Still Foolin` with Fora # 1.I lost track of how many different Venturis I had made .They were all different in some way.One of the more Wierdo attempts was this one .One of the pics shows a fuel jet angled to the center of an enlarged venturi.The pic shows the Tube hanging way out .But after soldering it was ground down so the spray bar would fit when ,the whole deal was installed.Everything I tried didn`t make any drastic improvements,That`s the Bad news[:@]. The good News ,there were no Drastic, Decreases in performance, either.Most of my venturis, ended up as scrap ,due to Shortening the overall lengths ,and reaming out, the Main Air passage, as well as opening up the fuel inlet hole, to the point of making the Venturi to junk....At this point ,no more horseing around with the venturis,untill I can find more Rpms, somewhere else.Then I`ll look at that Dept. again..

D Bronk

While working on Venuris I also modified a needle and spray bar..Again no big power gains ,but it did help with making tuning easier.By Sharpening the tip, of the needle, to a longer point,The adjustment was much finer ,than the blunt tipped needle.I also, had to change, the spray bar a bit.That part was shortened for the needle to bottom out. I also opened up ,the fuel outlet.That worked well with the Needle changes..But still, not the answer. for more RPMs.

Larry Driskill

But don't we all "know" there is something there.

Back when many CL Combat flyers were serious about Slow Combat I messed with venturis a bunch.

The rule in Slow was that you could not use a pressure fuel system. Yes, yes, I know - suction fuel in a Combat (or other high G) plane is dumb thinkin', but it was the rule.

So you needed a setup that would draw fuel when street variety suckin' just would not hack it. Chrome off bumpers and all that . . .

The best venturi I ever tried was a 'post' venturi. Actually the venturi itself was pretty standard, but the fuel spigot was a post that stuck out in the middle of the venturi and deposited the fuel in the middle of the airstream.

I tested many venturis on a simple setup that used the vacuum cleaner for suction and measured the effectiveness of the venturi by how far it would pull water vertically up a clear fuel line.

The good ones looked something like your reject.

D Bronk

...Well it`s good to hear, that the center venturi injection ,worked for you Larry .I haven`t totally given up, on the Venturis yet .Once I find some Rpms ,I will look at those experiments again. Then at a higher Rev, there may be enough of a positive effect, to Use one ,or some ,of those venturis again.Next time, I won`t Butcher them up.. I`ll just make, more ,&,Different Styles....

...I`ve started making more Mechanical Changes again also,mainly in the Cylinder head Dept..So far ,I`ve shimmed the Cylinder up,Shaved a few thou.,off of the Cylinder base.I`ve jacked(shimmed) the Head up, I`ve dropped(shaved), the Head Down..,.Tried different Nitro with all those changes.Right now, FORA #1 ,has the glow element sitting 0.025" from the Piston face at T.D.C.To get the piston Closer to the head..I can shim the piston up..The problem is, I can`t seem to get the engine to Break 21,000 RPMs Barrier.[:@].I now think all my earlier Tach readings were Bogus ..I`ve been Running the tests,in my Basement ,and have been useing a flashlight, for the light source..I believe my readings are correct now..Fooling around, with the head ,and moving the cylinder around,useing different fuels, there has still not been a Major power gain..[&:]

...I`ve pretty much Tried everything ,I can think of, to the point ,that I now, have to start working over, the cylinder ..But First I`m going to Swap, part ,by, part,From Fora #1 to, #2...FORA # 2 ,won`t break the 15,000 Rpm Barrier..What I`m, going to be looking for ,is ,if any one component ,in particular, makes it come alive.Example swap modded Crank, for stock Crank ,test it, then Change it Back,and so on..One thing at a time..


...I`ve got ,some Hot plugs, coming From Larry, along with Foras #5,#6,& #7..I just hope, they`re not going, to, Keep them at the Border, so long this time.Dangerous Goods you know

...I`ve got ,one of Skaliwags ,TEE DEE 0.020" so, I`m going to figure out, what the timing is ,on that engine, and Compare, with the Foras`,.I`ll most likely, take a few days, and, think things through,before, I go ,Hacking on the Cylinder..Maybe the Hot plugs will show up before ,I get on to this..There`s definately, a rich Burn, on the Glow plug ,as if ,there`s too much intake Duration..I have a few ideas I want to try ..So, Hopefully something clicks ..

D Bronk

Oh Yeah ..I`m going to "Stuff " the Crankcase yet too.See what that does for #1 ..

combatpigg

My Feedback: (3)

Full size engine builders in top notch shops use either a torque wrench reading or an amp gauge reading [ off of an electric starter] to determine how much effort is needed to turn over the bottom end, then check to see how much cranking effort is needed to turn over the fully assembled engine with the valves adjusted. for these tiny engines, we need a very sensitive way to gauge the same thing.

D Bronk

Cp.I used My sensitive fingers by dropping the cylinder I think I hit a New pinch.Took a while spinning the engine over, so that it would start.It got tight..