Toad

I flew it. I was slightly disapointed and at the same time I was pleased about how smooth it ran.
On the 4.2x4 APC it only spun 28,500
Then I ran it for a short run using a 4.6x2.8 glass prop, it tuned this prop 32,500+ on the bench.
I flew the plane on the APC. I hate how that prop pulls so poorly through pylon type turns.
I used 40% fuel and the 97t turbo O'Donnell medium plug. The plug held up for the test tank and the flight and the bench run on the glass prop.
In fact, the plug looks brand new.. I heard talk that the stock head can handle up to 60% nitro without trashing the plug.
So, from the look of this plug, I am thinking I can raise the compression some and I may change the timing a bit, to see if I can get it to turn better rpm's
On the good side, the thing runs very, very smooth.. Impressivly smooth and there is room to play with the compression and timming.. I think maybe this thing
will be a great performer. For pylon racing, I think the 4" pitch is just too much for these motors, THe airplane I used is very sleek, but still, in the turns, that prop is a dog, on the straights it gets up and goes well, but you lose too much in the turns with it.
So, in stock airplane form, no internal changes, this is a smooth runner. To make it competitive, some work will be needed.
thats my 2 cents worth on it.

MJD

My Feedback: (1)

I wonder if the combat standby 4-3 to 4.25-3 trimmed from a 5-3 would work out.. it's in the right direction, more revs less pitch.

I never hear mention of anyone using the APC 4.5x3.5. Sounds like a similar load to the 4.2x4 but more blade area and less pitch. Wunner if that would turn better?

And I've been staring at Steve Wilk's prop list, there are some candidates on there maybe? In diameter/pitch combos anyway, such as 4.5x3.25, 4.625x3.

MJD

Toad

One of the racer's here, he runs the APC 4.5x3.5 combat/pylon prop, and he spins that over 32k, his plane is very fast on it. Unfortunatly his crank broke he says in his picco
I have several different props I got from Larry, I will bore the hole out in a few of those to try and see where the sweet spot is.
The GZ is stronger from what I seen today. ( I had a reworked new GZ there today also)
I am thinking the red, 4.6x3 prop is going to be the ticket for the Picco.
I have looked at Wilk's offerings, I need to try a few of his...thats all I need is more $ props laying around here...
I remember my old CS/GZ from the old days turning the 5-3 tornado over 30k... Im thinkin I may just go back to that prop just to see if the Picco will spin it over 30k. if so I m thinking that would put me in the middle of the field for speed and if the picco can hold up.. all would be good enough for this class. untill they allow the Cyclon's and the like.
What I like about this motor is the fact that of the 5 I have played with, they ALL are the same, same in pinch, fits, etc.. I really like that over buying 5 GZ's to get one good runner. I wish CS/GZ would get their collective s%^* together on quality control

DeviousDave

Really think y'all should try the APC 4.1-4.1 electric prop....

Japanman

It all sounds really promising. I wonder if tempering the crank in the toaster oven (or better) like you told me about might help it hold up. The crankweb in my engine looks thicker than a norvel 061.

S

Toad

I just think Ron is kinda rough of things ..if ya know what I mean, it probably fell out of his pickup with no tail gate on the way to his alchy still. Hit a rock and broke the crank.
IT is the only crank I have heard of that has broke in the Picco so far, I hope it is not a common occurance as we start to abuse these motors here.

RocketRob

My Feedback: (1)

My name is Rob, and I failed a picco crank.

I uh had one fail in diesel operation due to a sloppy prime[:-] This is also the one which spun up to 36k on several occasions on the mistaken 4.2x2 prop.

Crack started right from the 90degree corner in the crank opening - go figure, not a lot of meat there.

AndyW

My Feedback: (1)

Stress riser,, why do they do that? Seems to me it's easier to do it the Norvel way.. nice, round corners. I asked Cox one day and they said that it was easier to make sharp corners. ??? I had a Cox TD crank fail but that was after many dozens of cracking the throttle open when working with carbs and acceleration.

And I wonder why Picco went to a 7mm crank? Norvel added a half millimeter,, good move but bad for bearing selection. And 8mm is overkill for .049/.06,,, or is it. Maybe an Imperial size? Last time I miked a Cox crank it was an oddball diameter. Why'd they do that?

But any way, once I'm done testing the Fora, I'll be testing the Brodak/Picco hybrid on diesel. If that one breaks,,, [:@]

AndyW

My Feedback: (1)

Here's Rob's crank.

Toad

The reason why Picco went with the 7mm crank is because that was a rule stated for the car class of racing it was intended for, in an effort to slow things down.
Well, that class of racing failed due to lack of interest, Picco only made 2000 of these engine, for the USA that were Pre-Paid for by Ofna and only a few extra parts. Now Ofna is selling the things off trying to re-coup part of their investment.
I went with a 8.5 mm crank in my homebuilt, just so I could get a good size fuel passage like the GZ uses. Probably overkill like you say.
You can make the crank easier with a squared corner cut for the venturi window. To go with a radiused corner, I had to cut that window with the side of the end mill and make a fixture to time the thing sideways in the vise, it would be much faster and easier to use the face of the endmill cutter. To cut from the side, a small endmill cutter is needed, often costing more because they dull faster and break easier, and you cant simply take one or two cutting passes and be done, you have to really go conservative on the depth of cuts, increasing the time it takes. Better to go with the easy route. Norvel uses a larger cutter in side cut mode , but the radiused corners are way to large, making the window not so crisp in its function.. anyway, I can see both sides of the issue.

Japanman

I would think that if these cranks where fragile, we would have stumbled across rants from car guys who broke them. I have watched a few youtube vids of rc cars with them in and they really rev-out in a car on a straight, which i think would really load the cranks up.
they also have a flywheel on them and when the cars change direction quickly or just porpose over bumps, they must test the crank also.


I could understand why the 7mm crank might not hold up as a diseasel though. Rob: are you maiming innocent engines for your own sadistic pleasure? what other engine crimes are you guilty of? repent now, before it is too late and stop your moral slide.
...And don`t think that blaming it on Andy W will help your case.

S

DeviousDave

Probably was the minimum diameter needed to meet the durability requirement for the average to semi-advanced flyer. It's not like these companies have people like you in mind when designing engines so that people can install ball bearings during a long, cold winter. A plain bearing case allows you to make the lightest crank you need to get the job done. Or, it may have been that they wanted to work with a certain size of stock on their screw machines and the finished sizes were a result of the starting diameter.

Toad

Actually, the 7mm crank was determined to be the largest allowed for this class in car racing, it was simply a rule.
I think that if picco wanted to make an .049/.061 size for the 1/2a folk, they would have went a bit bigger on the crank.
Not much of a market in 1/2a. I am surprised that Ofna even dared to do this for the cars.
I am glad they did, I think these little guys are gems, Cant get a BB 1/2a any cheaper right now and the parts are excellent.

Japanman

I could not agree with you more. these are $$$ engines, and for $50, they are a steal. I would happily pay $120~$150 for an engine as well made as this.
I think engines like this are hard to appreciate until you have had one.

S

RocketRob

My Feedback: (1)

Guys, don't think of it as a weak crank, but think of it as a very strong rod

AndyW

My Feedback: (1)

DISEASEL ??? [:'(] Damned if I didn't split a gut and spilt my coffee. Them's fighting words. [sm=devious.gif] Just for that, the FORA is going to have the glow plug issue solved in anudder way. Especially since I saw what a bullet proof rod is in there. And I have no doubt that the crankshaft will hold up. [:@]

Car repairs have got me bogged down. I do my own, mostly, but brakes,, blew them the other day. I just need to splice in some good line. I know double flare fittings are the proper way but some guys are talking compression fittings. Legal? US? Canada? It's a 91 Corolla wagon.

DeviousDave

I was speaking more to Cox and Norvel which were discussed

Toad

Ah!

I get ya now Dave.... Brakes? hell if it slows ya down some they must still be good...Andy...who cares about legal these days anyway...oops I better stay on topic

DeviousDave

I'm reporting your post to www.whitehouse.gov.


I wonder if it would be worth making new prop nuts that have a threaded portion of the prop nut extend into the prop hub to make up for the short length... Making one or two wouldn't be a huge project, making 20 would.

Toad

that is exactly what I do on mine dave
I have the lathe fired up, the program wrote, Im ready if folk want a few.
I make that spinner in two styles, one for the APC brands and one for the Glass props Larry sells
I can also make the drive plate, And now I am working on making the split collett. THe OFna stuff for this is just too big and heavy for my liking,
Oh I can make the Head also that replaces the huge car headsink.

If anyone is interested. The GZ collett is what I want to buy, but so far I cannot seem to get the distributor to get back to me on those, so I will make a few, but damn Im slow on those.

P.S. The glass european props, that Larry or GRS sells need the prop hole bored to 6mm to fit the spinner's and the .236 ring that comes with the apc prop should be used on the APC's, or you can use the heavy Mecoa spinner and use the stock APC drilled hole that they say dont use, as they dont drill them on center.

DeviousDave

Nope. He's creating spare parts for his other Piccos![>:]

Toad

I made a venturi adapter that allows the use of the TD .049/.051 venturi and needle assembly. I ran it, it works with one major drawback.
No matter how I position the needle body on the engine, the fuel line is placed right in front of the exhaust port, It gets charred or melted each run.
I decided it is not a good option. It would require a fuel line change too often, like in between heats at a race or god forbid, have the line melt in flight and making the fan stop.
I was hoping this would work out well, as it would have alleviated the problem of finding suitable needle assemblies to use.
So, I am stuck with using the GZ needle, which I dont like very well as it is too coarse for my liking.

DeviousDave

What about using a VA needle assembly from Larry? Or how about a heat shield made from shim stock?

Toad

The 4mm spray bar that Larry sells is just a bit big. IF I bore the hole out to that, there is very little meat left to hold the thing, I think it would break out on the first run.
There is barely enough wall thickness left after boring that hole to use the 3.5 mm GZ bar.

planebuilder66

My Feedback: (8)

Do not use compression fittings on brake line, only double flared ends allowed, for a good reason, the single flare and compression fittings will leak and fail.