mr_matt

My Feedback: (10)

First congrats to the guys in NY with the MIG, that is a great accomplishment.

I have been meaning to post what I heard at Superman about the gear. Now let me start by saying I have only played with the gear, I have not tried anything, my friend Rob has and he is thoroughly disgusted at this point.

I spoke with Larry Tudor from Planes Plus/Fiberclassics. He has spoken with Wolfgang on several occasions, trying to get some insight as to why Wolfgang can get the gear to work when basically no one else can.

Anyway in talking to Larry, I think I might know what is going wrong. According to Wolfgang, bleeding the system (purging the air) is a very critical step. With the plane held in many different axis, he has to cycle the gear 10 times in each one (in order to try to get the air out).

The reason this is important is because of the way the ECU senses the position of the gear and doors. The ECU can actually measure the load on the hydraulic pump motor. The load varies when the gear (or doors or whatever) have hit a stop. That is how the ecu know to sequence the valves.

THe problem is an air bubble in the system may be enough to cause the ECU to think a sequence has completed when it has in fact not. And then you get the confusion. This is consistent with what Rob saw.

Now I have an idea to completely replace the ECU with another one, made from a small computer called a Basic Stamp. The basic stamp can easily recieve commands from an RC reciever, and send pulse width outputs to a number of servos (for the valves) and to an amplifier (or RC speed controller) for the pump. THe difference is we would set the Stamp up to read in limit switces on all of the gear, both up and down. If enough I/O pins exist, then even read the position of the doors and speed brakes as well.

Of course another option is to add a mechanical up and down lock to the gear (I have an idea for that too) and use air. Rob feels that air pressure is plenty to operate the gear, the hydraulic is used in lieu of the mechanical locks.

Anyway that is all I know. Fiberclassics showed a lot of interest in fixing this at Superman, I guess time will tell. I keep waiting to start mine until all of this blows over.

Sorry if I have gotten any of this wrong, just trying to pass along what I have heard to my fellow MIG 29 owners!

David Gladwin

Matt,
Even Wolfie was having trouble with his gear in Thailand causing him to scratch round three.

I am sure that the gear can be made to work but we need to make it work with complete reliability before it can be considered airworthy.

I have serious doubts that we can lock the gear down with air pressure as any rearward load on the leg will simply compress the air possibly causing it collapse.

. Anyway I think the pressure is on FC to give it theit attention and we are, with the support of some othern decdicated Mig buliders, getting there !

Thanks for your input.
BRG,
David Gladwin

mr_matt

My Feedback: (10)

David said

<<<I am sure that the gear can be made to work but we need to make it work with complete reliability before it can be considered airworthy.>>>

I personally believe that the gear CANNOT be made reliable with the ECU/ pump current sense technique, I think it needs limit switches. That is my whole point


<<<I have serious doubts that we can lock the gear down with air pressure as any rearward load on the leg will simply compress the air possibly causing it collapse. >>>

As for the air gear I agree, reread my post, the gear would have to be MODIFIED to add a mechanical lock in both up and down position. I already figured it out with the mains but I did not look at the nose.


<<<Anyway I think the pressure is on FC to give it theit attention and we are, with the support of some othern decdicated Mig buliders, getting there >>>


I think the best bet is Larry Tudor, if anyone can figure it out he can. As for continuos pressure on FC, my moto is you cannot get blood from a stone, if they were going to fix it then why haven't they already?

David Gladwin

Sorry if I missed those points Matt.
Limit switches should not be too difficult but perhaps the addition of a hydraulic accumulator as on fullsize hyd, systems might also be a partial or even full solution using a pressure switch on the accumulator to switch the Hyd pump.
BRG, David G.
(not to be confused with another David who is getting some stick on another thread !)

Jetkopter

My Feedback: (1)

Hello Matt, The secret to getting the air out of the Leimbach hydraulic pump is to run it at around 4 or 5 volts until all of the air is out of the system. When the pump is run at 7.2 or 12 volts the rpm of the pump is around 6000, this causes the trapped air to foam and you can not get it out. I tend to agree with you that the current ECU will not work. Andreaus informned me at Superman that the english instructions on programing the ECU are not correct Even if we have the proper instructions I would bet my last buck that no two of the pumps operate the same.The operating theory behind the ECU is when a cylinder reaches the end of its stroke and load the pump motor increases, causing the ECU to see increased amperage draw from the pump. The problem is unless you know what that value is and are able to set the relief valve in the pump properly, the ECU will never work. I asked Bob Wilcox to see if he could get the specs from Markus Zipperer. I know Bob is very busy so maybe remind him about it and we could put our heads together to make the ECU work.

Don DeSandre

tahfiet

Hi David!

I think you are wrong: It was not Wolfgang who had probs with his gear in Thailand. He didn't manage to start his engines in round 3 because they were flooded with kero and the glowplugs were on the bottom. What a lucky guy... . It was Dave from Thailand who had the problems in round 2, but managed to fly it in round three.

He now flies his 2nd MiG with the hydraulic-gears and Inever saw them fail. I know of another guy here in germany who already flew his Mig with original gear and built a second one for the japanese AMT-distributor. Maybe I can get his e-mail or phine-number to ask him how he managed to get it work.

Greetings,

David

David Gladwin

Hello David,
I would appreciate his e mail address ! Yes I remember Wolfgang had flooded engines but I aso saw his gear collapse at one point.

TheThai entry was damaged I believe after leaving the runway which caused him to miss round 2.

Your input is much appreciated.
BRG,
David Gadwin

fred cesquim

Cheeres gentlemen!!
seems that we are getting near a sollution!
pity that F/C don´t enter the forum to update what´s going on there. even haven´t replied my e mail...
i had to stop mig building because i´m graduating in the next month, but as soon as i finish the university i´ll be over the gear, and thanks to all efforts of modellers here we will have this awesome plane flying!
thanks to all of you for helping each other and for running this nice forum
regards / fred

mr_matt

My Feedback: (10)

Hi Don,

Congrats on your efforts, perhaps this will inspire Rob to finish his, I am not even opening my box untill he get about 50 flights!

I would not hold my breath on that ECU, but I will mention it. As I said earlier I think the key is limit switches.

What turbines is he running?

Jetkopter

My Feedback: (1)

Hi Matt, The MIG has a pair of RAM 1000's for now, down the road I hope to see a pair of P-120's in there. The plane is weighing in at 53 pounds with fuel, he needs to find some really light weight paint! I gave Rob my number if he needs hydraulic parts or more info so keep after him to finish it. Besides his hotspot is starting to look really tired!

BRG,
Don

Gordon Mc

My Feedback: (11)

Just in case you folks with the 29's don't read all of the threads on this forum ...

A post about some fancy-looking brakes in a South African Su-27 led Marty (ozcan) to realise that the guys from Bay Turbines claim to be using hydraulics too, so are another possible source of info / solutions.

The thread is here: http://www.rcuniverse.com/showthread...619#post372423

Good luck guys !

Gordonn

Jetkopter

My Feedback: (1)

You might has well give up the idea about complaining to Fiberclassic's! Don't you think if they wanted to do somesome thing about it already they would have.Use that energy and effort to do something constructive.....there are too many people here that just want to complain about anything and everything.What serial number is your MIg kit ?

JET FX

Gordon- FYI I have sent Bay turbines an email re- their hydrualics and SU27 explaining the interest in their system for the MIG 29, being the weekend still! I will wait a few days for a response. There does not appear to be much mention of the SU27 and its systems on the Bay site, so I am pressuming the SU maybe a prototype. I hope to hear back from Bayturbines early next week? stay tuned.....

mr_matt

My Feedback: (10)

Hi Don,

THanks for the tip, Rob is plannin on 2X P-120s as well, should be a great combo.

FYI my serial number is 22, I heard rumours of issues with the wings in pre SN 24 kits, you know anything?

JET FX

Mr Matt- what did you hear about the wings? you've got me concerned! my MIG is #25.

Jetkopter

My Feedback: (1)

Hi Matt, no problem with the wings on Kit # 10 ! To tell you the truth my friend was going to sell the plane after it flew, but now after feeling how stable the plane is in flight he has changed his mind and is keeping it. I know there was a problem with the elevator pivot tube on the two MIGS we have here. The tube was not parallel and had to be cut out and an alignment jig made to correct the problem. Also major re-engineering of a lot of little stuff.
BRG,
Don

David Gladwin

One thing I will warn all Mig owners about are the mountings for the rudder hinges for which in my kit there was almost no support. (just 1/8 inch balsa)

I cut a panel to install a hard balsa block to carry the inner part of each hinge and inserted a strip of light ply up each fin and ridder to capture thee end of each hinge.
BRG, David Gladwin

LucasV_Jets

David, I'm glad you are bringing up a subject that many MIG 29 kit owners could be working on at this time.

ONE NOTE OF CAUTION -- it may be a good idea to reinforce the area you refer to, however, you should be very careful with any extra weight you add to the tail...

Remember, for every extra ounce you add to the tail there are an extra THREE ounces added to the nose. Further, for this plane, you should be aware that overall weight is critical.

In my case I put my hinges on with the same amount of balsa provided by the manufacturer (1/8" balsa) and achieved excellent results.

Good luck with this piece of work! I'm looking forward to hearing of your progress.

Best regards,

LucasV_Jets -->AKA: Kit #10

David Gladwin

Hi Lucas,
Overall weight increase was minimal and rather that than lose the rudders due to hinge mounting failure.

I have seen the Mig fly on several occassions and it is capable of very slow flight so I don't think overall weight is critical except for remaining under the limit for competition whhich is why Wolfie removed so many engine accessories.

With twin JetCat 160s (lack of) power is not an issue !
BRG,
David G.

fred cesquim

I´m just curious, how works the weight limititaion for competition?

fred / #23

David Gladwin

Fred, I think the weight limit is 25 kilos but see IJMC rules on their web site.
BRG,
David.

LucasV_Jets

David G./Fred,

David, you brought up a point I had not considered - I thought you would be using your MIG for competition flights.

Since you will not be competing, you are right, in your case, the weight factor is not critical as I know that this plane will accept a very high weight load.

Fred, for competition purposes, I suggest you go no higher than 55 lbs overall.

fred cesquim

Hello Lucas!!

nice to see you here!
indeed i plan to enter the mig at competition. the point is, i built for money, the plane isn´t mine, and i have to follow the owner´s direction. if he choose to compete, and that´s what i hope, i´ll go this route, anyway, i always put my best to build as light as i can.
i´ve just finished one plane for the brazilian competitor at TOC, fabio Trento, the aeroworks extra 300l and i managed to reduçe the weight in 1 kg less than his back up plane.
could you tell us how have you managed to make your gear work properly?
and thanks for the info David!!

regards/fred

LucasV_Jets

Fred, I'm still debugging the migs landing gear. I just followed the kits directions but did not use the ECU.

I used a combination of a speed control and mini-hobby electronic sequencing.

JET FX

G'day Lucas, I was wondering if not to much trouble could you post some pics of your MIG mods e.g. gear speed controller install set-up etc. or even a rough schematic drawing of your suggested mod would be great....

Cheers-