Build of Cirrus V8 (C Fellows design)

[Jo]

Simon, have you any slitting saws with a finer pitch on them? That one looks a bit coarse, which may be why it dug in  .

Jo

[PJW]

Hi, the other reason is that it is to far out of the chuck, like parting off you are better off as close to the chuck as you can get. that far out unsupported it will flex & grab 

[Kim]

Hi Simon,
That looks like some ugly ensuing mayhem!  Sorry that happened.  Luckily it seems that nothing important got injured! I always find it scary when stuff like that happens. I'm sure you'll get it sorted.
Good luck ,
Kim

[zeeprogrammer]

That is one scary picture! 
The image I have of bits flying around...time to review my safety procedures.

[sco]

Definitely guilty on the 'too much hanging out of the the chuck' charge but I think the bigger crime was that the stub being held in the chuck was too small.

Zee - there was just one bit of the saw that broke off and it didn't go far - I've had more dramatic breakages in the past where the blade has shattered and the bits spread all over the workshop but the bits are very light so I think the risk to life and limb is small 

Anyway strike two went ok so I now have a full set.

Simon.

[sco]

Drilled the camshaft air passages this afternoon - despite the drawing notes and Chuck's expert guidance all did not turn out rosy.

You probably need to review the plans for the engine to understand the following - in brief the cam shaft works as a rotary air valve to deliver air to the individual cylinders when they are at TDC.

I fitted the timing wheel and checked that at the angle on the timing sheet the crank pin for that cylinder was at TDC - everything lined up so set the wheel to 0 deg and drilled the first hole.  Without thinking I then saw there was another hole drilled at 0 deg so without turning the crank I drilled that one too.  I repeated this pair of hole drillings for 90, 180 and 270 degrees - when all was done and I was feeling pleased with myself I extracted the cam shaft and only then noticed that there seemed to be more holes on one side of the shaft than the other - doh - because of the 2 to 1 gear ratio between crank and cam I should have rotated the crank between every hole!

I'm not keen on re-making the camshaft so I'm going to try and plug the incorrect holes with epoxy and have another go.

Simon

[sco]

Been tinkering with the engine over the last few weeks - it seems close to a runner but despite turning over freely is more musical than motive;

<a href="https://www.youtube.com/watch?v=_dctknjOw3g" target="_blank">http://www.youtube.com/watch?v=_dctknjOw3g</a>

Simon.

[Jo]

I think I might recognise that tune I have heard similar out of my own engines   

Jo

[Don1966]

Bummer Simon, just keep plugging bud you'll sort it out. It's a nice engine and you have done a great job so far.  Awaiting to see it running.


 

Don

[Roger B]

I've only just picked up on this thread having seen the comments on the appologies thread. Good stuff, but I will have to wait until I get home to see the videos  .

[cfellows]

Simon, what length and wire-size springs did you use for the exhaust ball valves?  I used 9/16" long by .010" wire size.   If the springs are too stiff, the engine won't run.  Also what pressure are you using?  I usually run my engine(s) at full pressure (100 PSI) but use a ball-valve to limit the amount of air flow, opening it slowly until I can hear the air flowing, then gradually opening it more until I get the speed I want.  Also, are your slave ball  valves able to move freely?  If the tolerance is too tight, they tend to stick.  Several thousandths clearance is preferable.

Assuming you have all the holes in the rotary valve drilled correctly, from the video it sounds like the problem could be one of the following...

1.  You have too much air going to it.
2.  The exhaust ball valves are sticking.
3.  Your exhaust valve springs are too stiff.

[sco]

Hi Chuck,

The exhaust valve springs are 1/2" long by 1/8" diameter but I don't know what the wire gauge is - if anything I've been wondering if they are too weak such that with a bit of leakage at the rotary valve they are opening when they should be closed.  For air pressure the regulator is set to ~2bar which is about 30psi although I have tried it with ~4bar.

The slave ball valves were a bit tight to begin with and were definitely sticking but I'm pretty sure they are all free now.

Apart from stiffer springs and maybe remaking the camshaft I'm running out of ideas...

Simon.

[cfellows]

Simon, can you measure the spring wire thickness with a caliper?

Thx... Chuck

[sco]

Chuck,

The spring wire is 1/64" thick.

Simon.

[zeeprogrammer]

Been tinkering with the engine over the last few weeks - it seems close to a runner but despite turning over freely is more musical than motive;

I watched this yesterday.

I think you're closer than you think.
You're just tuning up.