twoturnspin

Hi,
I've got two isssues with an OS70 Surpass that I would appreciate advice on:

1. I run on-board glow (activated at 1/4 throttle) using a 1700mah NICD battery. It runs great for about an average couple of flights but then the engine just won't start but the battery has around 1000mah left in it when I recharge it.
How low should I be able to run the battery before I need to recharge?
If I replace with a 3000mah NIMH cell will this work better?
What voltage should I be seeing for the glow to operate correctly?

2. The engine lost a great deal of power so I checked the tappets and found that the exhaust clearance was too small and have adjusted out. Seems to have improved but it is not powering up as much as it should still especially when pulling on the upside of a outside loop. Also I am getting a "burbling" noise when the engine is running at full throttle.
Any ideas on how I can overcome these issues?

Any help here much appreciated,

Simon

loading

My first guess would be a bad glow plug. Someone correct me if I am wrong, but a fully charged Nicd should be about 1.4 volts and its dead at about .8 volts.

smokingcrater

how much wire on your onboard glow? too much resistance due to wire or bad connections and a single cell won't light a plug once the voltage drops some.

Carlos Murphy

My Feedback: (72)

You don't need ALL that battery, you may be burning up your plug. A C-cell will work just fine since your only using it at below 1/4 throttle.
One system I use on a S.T. 90 is a Radio Shack nicad D-cell and a toggle switch.
I turn on the switch, start the engine and fly with the battery on all the time. I have put four 15 minuet flights on the plane in one day and the battery still had juice in it.
My Saito 180 uses a C-cell nicad OBG system I made but it's set up to shut off at above 1/3 throttle, it will last all day as well but I must remember to push the throttle past 1/3 after killing the engine and turning off the receiver otherwise the driver stay's on and drains the battery.

The Ghost

Simon,
You dont say what type of fuel you are using. With full castor you will get quite a lot of carbon on the valves(backside) which will reduce the power output. How old is the engine (hours of use)? I have run many 4st engines for many hours and only needed to adjust the valves after about 1 hr of use and never needed to adjust after. As LOADING said Check the plug first even change it with a new one and check the engine. If you are running 10% nitro fuel you should not need the onboard glow.

Cheers.

DBCherry

My Feedback: (4)

Simon,
I agree with changing the plug, it may be starting to fail.

When you say a "burbling" noise, are you sure it's not detonation? Usually described as the sound of frying eggs. If it's detonation, it's due to a setting that's too lean. If it's truly a burbling, it sounds too rich. [&:]

Good luck,
Dennis-

FlyNBHappy

My Feedback: (7)

Simon,

I'm guessing that you're running no nitro or very low nitro with the problems you're describing. I run my Saito 4-stroke with a similiar setup (except my OBG is on all the time) on 0% nitro. To answers your questions:

1) Since you're OBG cuts off at 1/4 throttle, adding a 3000mah NiMH battery will just gives you more flying time. I agree with the earlier post by loading about your wiring. If too much wire or not properly soldered/connected then the drain on your 1700mah battery may be more than it can handle for a couple of flights. Even if your setup is correct, but your system does not cut off beyond 1/4 throttle then 1700 mah will only give you two to three flights at most. If this is the case, then the 3000 mah will solve your problem. Most standard glow plugs requires a minimum of 1.2v and up to 1.5v. I run a 4500mah NiMH C cell in my setup and it is good for at least five to six 15 min flights (my setup is fairly crude with minimal wires).

2) I get a "burbling" sound at WOT also when my Saito is set up to run rich at the start of a flight. But is it fine for me because it is with a full tank and it sounds fine after serveral minutes when the tank empties a bit and leans it out.

With the loss of power, I have no clue as to your problem.

Please let us know what you did to resolve your problems.

Good Luck.

Fly and be

twoturnspin

Thanks to all for the feedback, much appreciated. I have taken the following action so far:

1. Replace the glow plug (it was black around the rim but still glowed).

2. Adjusted the tappet clearance.

3. Checked the voltage (when it was about half full) at the battery - 1.20v and at the glow plug 1.11v. Not sure if this is an expected amount of voltage drop or if I should expect less of a drop, is there a rule of thumb here?

4. Bought another battery 2400mah NICD so see if this makes a difference, maybe the current cell is a faulty as it only provide 1.2v when half full.

5. Checked that the battery stops operating above 1/4 throttle with a volt meter - all good.

6. Note that when I heard the burbling sound it was a humid day - I assume humidity makes engines run richer?

7. Am considering installing a remote glow in parallel with the on-board system to provide additional power for the start up process and allow me to charge this cell with the wing installed.

Thanks again for all the feedback, I will keep you posted on the outcomes.

All the best, Simon

a65l

My Feedback: (17)

That's a bit of voltage drop there to the glow plug. Remember that the larger a wire you use, the more voltage you're gonna get at the plug. Also, dumb question but how large is your ground wire, and is is connected to clean, paint and coating free metal? I have Saito .56 with a remote glow setup, and at first it wasn't working. The ground wire was attached to apparently clean and uncoated metal, but after working the area with some sandpaper, the system worked just fine.

Andy

twoturnspin

HI Andy,
Thanks for your thoughts.
I seem to have good negative electrical connection at the engine, I suspect the main issue is wire diameter as mentioned by FlyNBHappy.
Still yet to test but will do so this weekend.
Simon

Stick Jammer

Not exactly. High air temperature and/or high humidity will cause a noticeable decrease in performance. Vertical maneuvers will be the most obvious. The air is less dense which causes a decrease in power during combustion. The prop also has less "bite".

twoturnspin

Hi & thanks to all contributors, just wanted to follow up and let you all know the result of the engine changes you all supported me with.
Started up ok and was running well, 9 minutes into the flight the engine cut and I found that I had no compression, the reason....broken inlet valve spring!!! How common isn't that!! So, with somehelp from my local hobby store in Brisbane, I was back in the air the same day and the engine ran really well.
Still lack power in outside loops for some reason but are just bringing the power on sooner and this seems to make up for it.
Again, thanks for the feedback.
Simon