Starting OS 91 HZ-R Engine with Srimok

[roypwee]

I have a new OS 91 HZ-R Engine which I was breaking in last week. Using a Dynatron starter, it started at first spin.

However, today was not so lucky, was trying the whole morning to start the engine, nothing, priming didn't work, unflood the engine didn't work.

Any suggestions?

Very odd that last week break in starts were very good.

[hookmaker]

Bunch of possibilities - If I were you I'd post over in the engine section - more likely to get response there:)
/Henrik

[aussiemick]

To get my HZ-R started it requires that I crank the engine over with the carby fully open for about 10 seconds, this allows the tank to pressurise some.

Once I have done that, drop the throttle to idle and power up the glowplug, it then requires about 2-3 seconds of turning over to get it going. After the first flight it does get a bit easier to start with the residual heat in the engine.

When I had the OS91HZ it would start much easier than the HZ-R.

Mick

[SJo1]

Aussiemick,
Do You use 30% fuel? if so, have You added that extra shim that came with engine?

I'll try My FBL Srimok with HZ-R after 1 month break, yesterday I made upgrade to Vbar 5.0 pro from scratch, let see how it will fly:)

-Samppa

[aussiemick]

Yep 30%.

I added the extra shim and left the original in as well. I flew it with the stock shim for a while but burnt a hole in the piston with a badly adjusted mid range. I added the extra shim during the rebuild.

I think the vibrations are less and the fuel foams less, I have extended the fuel line between crank case and one way valve in an attempt to pressurise the fuel tank a bit less. The tank gets so much pressure in it that no amount of sanding of the tank cutout in the frames will give clearance to the tank when pressurised.

Mick

[hookmaker]

Mick, I got two very important setup tips from watching Eckman tune a Srimok to perfection this saturday on the Srimok FunFly UK.:

1) Engine setup and vibration dampening: Setup engine, clutchbell stuff, dampening block and gear mesh as per manual. Do not tighten engine slider bolts completely. Keep clutch dampening block main bolt fully unscrewed - do not yet insert black dampener screws.
Start engine and idle without blades/paddles. With a finger, feel the frame just below the main shaft and on the back of the tail pitch arm. Give a sligt amount of throttle and down again to idle. Do this for a couple of minutes. You can FEEL when theres no more vibration. Once there, cut the engine and tighten all bolts. Install clutch block dampener screws. Remember that they MUST be filed down so that o-rings can be compressed. Check by measuring against frame thickness.
Check mesh, start engine and feel for vibes, if ok then all is good. If theres a vibration now, loosen screws and repeat.

2) Tank foaming (I have a moderate foaming still): Eckman told me that foaming is mostly due to too tight a tank rubber cap. I should go home and loosen it up. Start engine. If leaking tighten untill exactly sealed. Then it should be ok. I will try this tonight or tomrrow and give you some feedback.

/Henrik

[TJ Present]

With a finger, feel the frame just below the main shaft and on the back of the tail pitch arm. Give a sligt amount of throttle and down again to idle. Do this for a couple of minutes. You can FEEL when theres no more vibration. Once there, cut the engine and tighten all bolts. Install clutch block dampener screws.



Henrik:

When you raise the engine from idle slightly is the engine self-centering? So, what I'm asking in other words, I don't do anything but feel when the engine stops vibrating?

I am assuming the point of this is to let the engine find it's own sweet spot and then lock it down.

I have gone as far as spinning it with the starter but this sounds better. Am I understanding what Eckman is doing correctly?

:YeaBaby:

[hookmaker]

Your understanding it correctly. I wouldn't realy call it engine self centering although in a way it is, - but you can help it a little with your hands.

The point is to let it kind of vibrate into place, and that you feel by squeezing thumb and index finger together over top of frame above starter hex. You can feel when the vibes are at the lowest/gone.

Also touch index finger to back of tail slider. Oh, remember to loosen boom clamp too, just so that it is not tightened down.

/Henrik

[TJ Present]

Sorry to be so thick headed, but am I looking for a confirmation of those same vibrations on the tail slider. Also, why am I loosening the boom clamp? I'm assuming you mean the two front clamps that hold the boom.

Is it because the boom has its own vibration? I am assuming that the engine is not run high enough to turn the head. This is kind of idle plus, yes?

Tom D

[hookmaker]

You're not thick headed at all..:)

Oh no, run it up so that the head turns at a good speed (Just over idle, - NOT 1000+ rpm!). You need it running to get out of the idle which has a lot of vibration.

Just touch a index finger to the tail pitch arm (black plastic). You loosen the tail clamp so that the boom is only fixed tightly to the boom claps in the body, thus you can better feel vibration comming from the engine.

/Henrik

[TJ Present]

I'll try this. When I first built my Srimok it was smooth as silk, no tank foaming. After an unfortunate encounter with the ground, I've rebuilt, but machine is not as smooth. Probably I caught the right spot for the engine by luck and now it needs some adjustment.

[aussiemick]

Do not tighten engine slider bolts completely. Keep clutch dampening block main bolt fully unscrewed - do not yet insert black dampener screws.

/Henrik

Henrik

I plan to attack this problem tomorrow morning.

I have the black clutch damper mount screws out, and the clutch bearing block bolt loosened about 3mm but still through the slot in the frames.

How loose should the engine mount bolts be?? Should the engine be able to be moved around by hand?

Mick

[Mercuriell]

YEs - loosen the pinion so it can move then engage it on pinion with ~ 0.3mm backlash, then centre the engine so it nestles in mid range or run it and adjust till it feels smooth - lastly adjust the clutch bearing block dampers - ~200° for your flying Mick !

[chasers]

Hey John, you reckon you gonna do a video on how to make adjustments on the engine mounts, and the tail boom clamp, etc? Coz i tried running the engine with the blades, paddles off and followed what eckman did, but still cant get it to vibration free.... A video definitely beats a thousand words!

:YeaBaby:

[TJ Present]

AussieMick:

Waiting to hear how you made out with your Srimok. Were you able to find a vibration-free spot for the engine position? I am planning to try this Eckman thing but still with questions. PM'd Eckman asking for some tips but he has not signed on to HF or RR for some time.

[aussiemick]

I had a play with it on the front lawn on Saturday but life got in the way of going for a fly.

I think I stopped some of the tank foaming, it was noticeably less afterwards, still has little "waves" dancing on the surface of the fuel.
I never spooled the heli up for a reference to know how much vibrations were present where I had the engine mounted before so am not sure if the vibrations in the frame are less, I think I got the heli as smooth as possible.

The thing I did notice is the VBar sensor getting the living daylights shaken out of it, it was a blur. Not really sure how I have been able to fly the heli up till now :dontknow
The vibrations were worse when changing motor rpm's so I am going to give it a try this weekend and see if it is ok with blades on and constant rpm's.

I have to pull the cyclic servos out of the heli to get to the governor sensor that is sitting too high to get a solid reading.

(if it was a farm animal it would have got shot long ago).

Mick