AA5BY

They are not the same. The footprint however might be similar as the hole spacings aren't very much different. The wide two mounting holes are only 1/8 or so apart and the narrower two are about 3/8 farther apart on the 35.

GEORGE_32

[&:][&:] they change their ignition and they didnt put ... the resistor... inside... ?? holly crap ....its like they open a hole for their company to fall inside... i think jimeni in oder posts has photos of opening the cup put more solder inside ,
one question are you flying in 2,4ghz ?? also what octane gas are you using...??? because if you are in usa then you have to retard the timming all the way down ..... (lower octane ...lower timing )
from where you bought the engine ??
is this the north american version ?? ( mine is not...) + dimes 49 didnt had any problem we both bought from sdshobby ... and these engines are not north american ... we also use 95 octane gas (its the lowest that i have in greece)
and if its only a resistor i would like to play a little trying to put the resistor and also make a good soldering job + test of reliability prior to throw the ignition in the garbage .... (peakmodel sbach 342 25% )
also if any one else had problems.... please post!!!!!
and when any one used the rcxl if they change the timing to 28.. deg you can eat the bracket a little to achieve the timing... ( i hope ....[8D]
[X(] )

AA5BY

I'm using 72mhz pcm receiver. As I noted, I don't think the RF problem I had was getting into the receiver as the throttle and rudder servos operated fine. The elevator servos however went hard over, each clockwise driving the elevators opposite directions... so my thinking is that the RF was getting into the servos but not receiver.

I didn't check the timing after changing to RCexl... the engine started and runs fine positioned where the original sensor was. No more RFI or missing or inability to reach top rpm.

I purchased mine from Cermark, USA. I assume it is a North America version.

btw... the plan is to maiden the plane it is in this weekend weather permitting.

pe reivers

It would not hurt to check the timing of the rcexl. Sensor design makes a difference sometimes. Base timing is 28°BTDC. More compression = less timing; lower compression = more timing
OR
High octane requirements is less timing and V.V.
OR
Higher octane fuel than required = more timing

GEORGE_32

,........35mhz and 72 mhz has issues with ignition greate interferance something that solved with the 2,4ghz (almost)
also thats why i think they say in many manuals to put the throtle servo 13cm away..from the engine , ignition...
also they recomend to use servoextensions that are twisted help more from interf

pe reivers

If 35 and 72 MHz have problems. Solve these first before switching to 2.4GHz
That is what all radio suppliers advise!
Solve problems first, then go to safer systems.

AA5BY

I agree... it won't hurt to check the timing and see where it lies. Will do so when removing the cowl to check muffler bolts after a few runs.

The engine and plane that it is in did get its maiden yesterday. It powered a 16.5 lb sport plane adequately using a Vess 18x8 prop. Maiden can be seen at

http://www.youtube.com/watch?v=QINu1...ature=youtu.be

The plane is a self designed, scratch built, mid wing with open cockpit sport plane.

btw, the range check with engine running with the RCexl ignition showed no signs of RF interference and this with the flight batteries located forward in the fuel tank compartment so not too far from the ignition unit.

pe reivers

Nice plane. The 18x8 is a little small for a 35 engine. 19x10 would be more like it.

91zulu

My Feedback: (2)

And it sound rich too..

AA5BY

Yep... it was rich. I flew twice today and leaned it a tad and it both performed better and sounded better.

I've got a couple of other prop choices here to try... I've an APC 19x8 W and some Zinger 20x8. The Zingers are wood and will fit the spinner ok so I'll try one.

I want to verify the timing too... so will do that sometime this week.

AA5BY

Catching up on a few things since last week.

First, yesterdays outing suffered a flame out. I'd just done a high hammerhead, which misfired twice on the climb and died on the down line. Fortunately there was plenty of height to land dead stick front and center. An immediate check showed no sign of high temperature. The cause is likely (as I've not run it yet after the discovery) the pickup sensor case had shifted back in the mounting bracket and was behind the magnet. Moral here is simple... glue the case to the bracket after aligning it over the magnet. I'm referring here to the RCexl pickup sensor.

Second, Pe had suggested it a good idea to check the timing after changing to the RCexl so with cowl off, that was done. It was my first time to do so and I'm slightly unsure of the technique as TDC seem arbitrary a couple of degrees. What I mean is that the piston lies at top for a period after reaching and before beginning the descent. I chose to mark TDC in the center of what I'll call the top deadband. If it should be marked at the beginning of the top dead band when it first reaches the top, then my figures will be off a degree or so. At any rate, I read 25.5 degrees where the test buzzer goes silent. Is this slightly late timing? Should I adjust to obtain 28 deg.

Third... Pe suggested the engine should have a little more than the 18x8 Vess prop running at 8250. I tried a Zinger 20x8 that was on hand and it tacked 7,050 and the break in suggestions want a minimum of 7500 so I've ordered a Vess 20A which loads slightly less than a normal 20". Question is, will the Zinger unload in flight and reach the 7500 mark? Is the 7500 threshold out of concern for break in temps?

pe reivers

The top dead center deadband has a quite well defined left and right if you rock the prop slightly. true TDC is in the middle.
26° is latish, but the engine should run tops and smooth with such timing. I use this timing on the Mokis, even using 105 octane (RON) fuel.
The Zinger will be fine once in the air.

I don't know why the 7500 lower limit. The fields we fly at, would have a 7000 rpm upper limit to keep the noise down. If you tune the engine on a gas mix with some extra oil, go fly as soon as possible. Use light loads with occasional short bursts of power. Heat will then not be an issue.

Jimeni

Lol!! Sorry to disagree, but the only place a Zinger is fine, is stirring paint .

AA5BY

Buttoning things back up after securing the pickup sensor, the engine ran fine.

As to the timing... Redoing the procedure to verify my numbers, I was more careful the second time to find TDC and more careful with carrying the marks back through the center of the timing disc and perhaps the larger issue, the play in the timing disk on the mounting screws was secured. The result was a read right on 28deg.

In four flights, there has been no hint of overheating.

The Zinger is mounted... will give it a comparison try. I've also a Vess 20A and Vess 19A coming to try.

pe reivers

You just showed your ignorance of the properties of JZ propellers.

Jimeni

Compare performance specs of an equal size Vess, Xoar, and Zinger on the same engine. I saw the same results on 5 different engines, on the stand, and in the air. I will put my 30 years as an aircraft mechanic behind these findings.

This is not a personal attack on anyone or their opinions. If it comes off that way, I apologize. I spent alot of time (and money) testing props, and probably get a little over passionate about it. I guess, as always, it boils down to personal preference.

pe reivers

I have had very good results using JZ props. Their problem is, that pitch denomination seems different due to the used airfoil. When comparing props, use a Zinger with about 1" more pitch, and get the surprise of a lifetime. Good for stirring paint? Maybe in the American way. Otherwise, no way! They have a character of their own. Consider that, and they serve their purpose very well indeed.

Jimeni

Fair enough. To be honest, I have never tried extra pitch, nor stirred paint with one. I always compared pitch to pitch. And now a Vess fan to the end.

pe reivers

Vess does not mention pitch. Maybe he is wise to the American way?

AA5BY

Comparing the Vess 18x8 to the Zinger 20x8 flight performance, I'd say the Zinger yielded slightly better torque with better up lines and quicker acceleration on takeoff but less speed on the flats.

Of some note is there was almost no left drift on up lines with the Zinger. The left drift is not serious with the Vess but does require some rudder correction.

There was no overheating problem with the Zinger running at 7,000 static. Immediately after landing, head temps were fine. As to noise level, I'd say running the Zinger was quieter but not by a great margin.

pe reivers

Good info.
I guess the Zinger turned a few rpm less than the Vess as well?
Vess 3D props load the engine a lot lighter than their standard props which are numbered.

AA5BY

Yes, there was a 1200 rpm difference with the Vess 18x8 running 8,200 and the Zinger 20x8 7,000.

For this airplane, I preferred the Zinger slightly because speed is not a goal and at 16.5 lbs it benefits from the better torque prop in the up lines.

I received two other props to try... a Vess 19A and 20A.

Jimeni

20A = 20x8. That will be a much better comparison. I use a Vess 20A with an SPE 43 on a 13.5 lb edge 540, and it is a rocket in vertical.

pe reivers

Can't judge 3D props by pitch only, because it's twisted in a special way. Compare with Vess 18x8 = yes though, because it's not a 3D prop. I'd bet the engine of AA5BY is more like 30 - 35cc, judging by the numbers.
OOPS, it's a melody 35

AA5BY

Jimeni... you were spot on... the Vess 20A is hands down the better prop tried so. 16.5 lb plane with 96" wingspan - MLD-35 at 7,250 rpm static. I'm super happy with the performance for sport aerobatic flying (no 3D).

As to the MLD-35... what a great running motor at least with the RCexl ignition. It is not hard to start cold, but after the first start of the day... it needs no choking and starts the first flip. If it proves durable... it is a winner.