ajcoholic

My Feedback: (10)

Well, I have made good progress over the last few days working a few hours here and there on my twin 040 engines for my Seneca.

I started this thread to document the engine and plane construction....

So, here are the engines so far, I have the cases done and the cranks are machined and silver brazed together. Everything so far is the best I have done (and I have made about 15 of these over the years) and the cranks fit into the cases with no binding.

Next I need to machine the drive washers and some trick piloshed aluminum spinners. I have decided to make an exhaust collector and try and fit some sort of carb to these for at least some sort of throttle action.

In the pics you can see the dual throw crank assembled, the jig I use to align the parts for brazing, and the offset turning fixture to hold the crank front and rear for turnign the crankpins. The props are APC 6-3's for scale. Also note (if you can see it) there is a tiny bearing bronze bushing ring in the front of the crank to take the thrust load. The intake is via the rear half of the case top, with the rear journal of the crank acting as a drum for induction of the fuel/air.

AJC

Bipe Flyer

Wow, you amaze me! That is so cool![8D]
How are we supposed to compete with that?

Are the con rods permanently attached to the crank?

You should post those pictures on the contest site.

DICKEYBIRD

OK, that's it, game over, fat lady's sung, last guy out turn out the light! Geez, let's start talking about next year's contest.

Awesome, Andrew....REALLY cool stuff. You is da man! [8D]

jboy381-RCU

i quit...i don't want to play anymore...i'm takeing my ball and going home...


AJ you beat all i've ever seen...the hobby gods are very prod that your here...keep going that extra mile...

john

ajcoholic

My Feedback: (10)

Well, let me say that there is lots to do yet...[X(]

This afternoon I am starting to tackle the plans. I have to scale the 3 view up to see what will look right for the twins, but I am thinking 1:12 scale which will give me a 39" wingspan will be a nice size. Maybe 1:10 which would give me a 46" WS would be nice too, we'll see. I want the engines to be a nice size respective to the nacelles.

Dickeybird, I am planning to try those AP 061 carbs on these 040 twins.

The biggest problem with these small twins is getting the crank brazed perfectly in line. If there is even 1/2 thou runout in the front and rear journals, the crank will bind and you cannot get the engine to run well. Been there done that. I took my time and it paid off, as these so far are my best two.

Yes, the rods are trapped on the crank, but thats the only practical way, as the lower ends are way to small to think about useing a strap with screws to hold them onto a 1 piece crank.

I am looking forward to this project more than anything I've done in a long time. It will also be my very first twin engined model! Talk about trial by fire!

AJC

Tim Wiltse-RCU

Gees AJ now I have to get my butt off this darn computer and get out to the shop and get working on my Sniper Disk Rotor engine... thanks alot!!


Later,
Tim

BMatthews

In addition to my idea for a special recognition for new designers I guess we need to introduce a MASTER'S class for guys like AJ and Tim..... They have to get TWICE as many of the popular vote to count for 1/2 the score

Bipe Flyer

That's why the first time designers and the master engineers all get the same prize, a spiffy T shirt.

ajcoholic

My Feedback: (10)

Spent many hours today scaling up some plan outlines from the three vies and photos. Here is the outlines so far. Done in 1/10th scale, 45.5 inch wingspan, and 6.5" chord. Going to be a decent size airframe, I have to keep it light!

AJC

ajcoholic

My Feedback: (10)

Well, I spent most of this afternoon cutting the parts for the wing. I settled on a hand-drawn "Clark Y'ish" flat botton airfoil for the wing. The full size uses a semi symetrical wing, about 13% thickness. I used a flat bottom wing for more lift at the slow speeds I think this plane will be more at home at, and since I dont plan on flying it inverted or doing a lot (if any) of anything but flying around in upright attitude, I thought it best.

I am using a dual spar (top and bottom) style wing, with the main members 1/4" square hard balsa. I am using three more 1/8" square strips on the top surface to help keep the covering from sagging in and provide some stiffness. The two wing panels will be joined by two 1/8" birch ply braces, and sheeted top and bottom out to the nacelles.

I AM going to go with flaps and ailerons, and am using the flexible sullivan cable to run them, from a centrally mounted single servo, one for both ailerons, and one for both flaps.

I have all the wood cut (I mill my own from balsa blocks I buy) for the wing construction, and all ribs are cut out (24 total).

Next build session I hope to have some pics that resemble a wing!

AJC

combatpigg

My Feedback: (3)

AJC! WOW! I'd pay to see that when your'e done! Actually I'd pay to just HEAR IT! It sounds like you have made some very wise decisions about how to do the wing. Do you have a target weight or wing loading figured yet? Do you think the fuel draw with the twin is proportionally better than with a single cylinder? I think the crankcase volume could be proportionally less with the twin, but the displacement of the descending piston is offset by the rising pistons' volume. It will be interesting to hear how well the AP carb works. Like I've said to ya before, it's a good thing that you're interested in model planes and not BOMBS!!![X(]!!!

MR Flyer57

Hey AJ,
What can be said?
This is the same kind of thing that happened last time, great planes and great people. I think you may have moved the bar up a notch or two, and may have moved yourself into a new class.[8D]

It is just this kind of thing that will make wearing the shirt a little more stylish.[sm=thumbup.gif]

I would like to be the first to warn you about the talented folks waiting and salivating in the wings. [sm=devious.gif]

Yes, thanks for stirring up the hornets nest of talent, Dickybird, Bipe Flyer, Matchlessaero and a host of other guys out there are now going to have to scramble to come up with a WOW factor that matches yours!

And where does that leave the mortals? It leaves me with the greatest time I've had since the last one! [sm=biggrin.gif][sm=biggrin.gif][sm=biggrin.gif][sm=biggrin.gif]
I will do even better because of the standard your setting, and am now without any pressure and still all of the expectation. Just being in the contest is a treat, and I can't wait to see what develops.

I can't remember which Star Trek movie it comes from (or if it is correct)

CRY HAVOC, AND LOOSE THE DOGS OF WAR!![sm=pirate.gif]

Great stuff and I will be in the hunt soon!! Got a planning meeting tomorrow could be some teams coming on line.

It doesn't get much better that this AJ!! GRRRRRRAAATE Job!!!!

MR Flyer57

littlefly

Hey '57':

That flick was "Star Trek VI - The Undiscovered Country".

[&:][&:]

ajcoholic

My Feedback: (10)

Combat pig,
In any two stroke opposed twin that I know of, the pistons allways rise and fall together (boxer style) otherwise you wouldnt get any pos/neg pressure to draw in fuel and air and also transfer it to the cylinder from the case.

If you look at my picture you can sort of make out the dual throw, 180 degree offset crankpins

The little 040 twin puts out allmost the power of a babe bee 049. It isnt a screamin' demon (unless you want to break cranks) but does run very steady, and it is more of a cool thing rather than anything else.

AJC

Nate-RCU

UNBELIEVABLE!!

There are many types of people in this world,those who think of doing it,those who talk about doing it,and lastly, those who actually do it.

A very keen fellow! Well done

Regards,Nate

Andrew

OK AJC, now that the intimidation factor is up to 106%, I have to ask: Since your are drawing your own plans and building your own engines, do you have a stand of balsa growing up there in the far North that you are going to cut, process and use in your construction?

Andrew

MR Flyer57

Heck Andrew,
Legend has it that ole AJ once had to sand cast his own bridge work and braces. And using the lost wax method, he had to replace the whole bottom jaw of he favorite coon dog!!

Really he's got a small but dedicated group of robots built, that will do half the work for him!!!
And as for balsa trees, he uses a high-bred, looks a lot like carbon fiber. Just look at the plane he made last year.

I really do believe that he was involved in Roswell, but thats another story.[:@]

MR Flyer57

ajcoholic

My Feedback: (10)

Nope, Balsa doesnt like 3 month long summers, and cold, long winters...

But I do like to saw my own. I buy blocks from a lumber dealer and it works out to about 1/2 the cost from hobby shop prices.

What I dont show everyone is the long LONG list of failures I have had, both in airplanes and engine work. I am just your "average" airplane nut amongst the rest of you nuts... and untill I have a finished Seneca, with two running 040 engines, well.... I dont assume anything will work out untill it does!

This contest is great. I thought I was done with building planes for this winter, but now I have to go and build another. Without the drive to come up with something new and different, I would never have decided to try this plane, and I have enough engine projects (that got bumped now for the 040's) to keep me busy enough. But I have never flown one of the twins I have made yet (they all went to collectors) so, I said hey, why not!


AJC

2fast4u

My Feedback: (5)

Almond Joy has nuts, Mounds don't. Call me Mounds.

MR Flyer57

Just attempting this kind of work puts you a little higher on the food chain. Failing isn't the worse thing, not trying in the first place would be!! It really is good your on our side and not making bombs for the trouble makers of the world.
You take a good ribbing and I hope all this good fun isn't taken to seiorusly!
We'll be comming back to this thread often to see what has happend.
MR Flyer57

ajcoholic

My Feedback: (10)

Yeah I can take the ribbing, extra sauce and all

So here is what I did tonight, didnt plan to work on anything but my girlfriend wanted me out of the house tonight, so...

I managed to finish the drive washers/prop washers and time and mill the intake (remember the rear crank journal acts as a rotary drum intake) passageways. Reassembled them, and checked for binding - everything is fine!

They look neat with the props and Goldberg 1 1/2" spinners. I may make some aluminum polished up ones later (thats what the full scale has), but these will do for now.

Now I need to make the exhaust collector rings...

AJC

combatpigg

My Feedback: (3)

HI AJC! Thanks for clearing that up, because I was scratching my head trying to figure out how you got pumping action. Even with your crank jig, is it a hit and miss proposition getting a perfect crank? Do you need to support the crank in the middle to get higher performance? It would be a real CHINESE PUZZLE to figure out a center support ! A split case is the only way I could visualize doing it. I've heard that large twins shake, do you notice any of that? I would like to get geared up to try some projects like what you are doing. I got a 9 by 20 CHINESE lathe from HARBOR FREIGHT, but it would be too sloppy for this stuff. I tried a SHURLINE to make FOX 36 combustion chambers, and it seemed like a good tool, but I would like to find a combo mini mill/ lathe that can work as finely as what you've got. Have you any recommendations?

ajcoholic

My Feedback: (10)

CP,
Opposed twin boxers are some of the smoothest running engines - big or small. I have made a 66cc twin and an 80cc twin and they are smoooooth. Dont know who would say otherwise, as the piston motions and weights are all ooposing and cancel out.

The crank is not hard to assemble and braze, provided your assembly jig is made accurately, and you know how to braze small things, with a small oxy/acetylene torch (have to just heat up the pin and web to get the silver to flow, and not heat the rods, pistons. ect or they will warp) I wrecked a few before I got it right, but after making about 12 or so of these I have gotten the hang of it.

The rods are so close together, there isnt room, or need for a center support/bushing. The front and rear journals of the crank provide about twice the support of a standard cox reed engine. Also, since the indiction is from the rear, you dont want anything to distrupt the flow of gas/air mix to the forward cylinder. The central web has a large hole in the middle to aid in the fuel/air mix getting into the forward section of the crankcase.

As for lathes, any good lathe that can work to a 1/2 thou tolerance can work. This engine can actually be made on a Taig, Sherline, etc as it is so tiny. The only thing you have to do that needs threading is the cylinder seats, and that is something a Taig cannot do.

Your lathe probably needs to be set up and adjusted, and any play taken out of the ways and such. Have someone familiar with lathes to have a look. Even a good lathe needs tuning up regularly.

AJC

ajcoholic

My Feedback: (10)

In anticipation of getting my AP carbs maybe by the end of the week, I decided to get cracking on the exhausts. I started with a piece of 3/8 by 3/4 6061-T6 and milled them to the correct thickness for the peewee 020 cylinders, then bored them and opened them up inside for the exhaust collector ring. Then I drilled the exhaust hole, and cut away the excess on the metal bandsaw. Turned the exhaust round, and finally cleaned them up on the sander, and bead blasted.

The cylinders, I had to mill flats on the top to accept a wrench, and then installed them onto the cases. They are lightweight, and should provide some muffling, and more importantly keep the plugs lit at anything under full throttle.

Also, the exhaust will be exiting the cowl straight down, to keep things clean...


I also did most of the wing construction on Sunday (yesterday) and have it framed up. Just have to do the tip blocks, and ailerons and flaps. Install the servos and sheet the tops.

Its coming along....

AJC

combatpigg

My Feedback: (3)

HI AJC! Nice job on the exhausts! Did you hollow them out freehand? The only info I barely recall reading about vibrating twins probably had to do with 180 degree firing designs, yes I can see how simultaneous firing would aid smoothness. 180 firing would spread the torque impulses out more evenly, but then you would be looking at 2 seperate engines coupled, which would be pretty bulky. Thanks for the info about lathes, I'm glad to hear that periodic tuneups are SOP. I have heard of a HEAT DAM material that is basically clay. It blocks the heat and be a sure fire way to prevent damage to the rods and pistons. Auto body repairmen used to use this stuff back in the days when the torch was king. Keep up the great work!