Author Topic: Two little CHUK's  (Read 4024 times)

Online Jo

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Re: Two little CHUK's
« Reply #15 on: August 31, 2019, 04:47:26 PM »
Have you tried offering them a Snickers while you eat the Pringles?

Jo
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Online Jasonb

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Re: Two little CHUK's
« Reply #16 on: August 31, 2019, 04:51:28 PM »
Chocolate is not good for dogs so I get to enjoy those too, though Double Deckers are my prefered bar.

Online Jo

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Re: Two little CHUK's
« Reply #17 on: September 01, 2019, 11:12:01 AM »
The cylinder is a fairly big lump to hold at 63mm diameter over the fins. I managed to hold it over two fins in Big C's three jaw chuck to face the bottom of the cylinder (forgot to take pic  :facepalm2:).  The important thing here is to make sure that the cylinder is square to the chuck and held nice and firm then the bottom can be machined flat. With a squared off base, the flat for the inlet port measures 27mm tall which leaves 1mm still to take off later  :ThumbsUp:

Time to swap over to the four jaw chuck and using the tailstock to secure the casting against the chuck all the jaws can be tightened up and everything checked to run true before looking to machine the top spigot. I'm going to follow what Andy did with his CHUK and use a fixed steady to secure that casting before boring :paranoia:

Jo
Enjoyment is more important than achievement.

Offline Alyn Foundry

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Re: Two little CHUK's
« Reply #18 on: September 01, 2019, 11:16:52 AM »


Graham, will you be building this one in much the same way as your first one or will there be any tweaks and alterations that you have found improve performance over the years?

J

Pretty much the same Jason.

However I really liked Andy's ( Chipmaster ) use of a cast Iron exhaust valve in his build. It might be a little more time consuming to do but the " lapping " time is greatly reduced. It also alters the sound, less metallic.

I'm keeping one little secret hidden for a while, associated with the inlet port shutter. This adaptation gives the engine a fraction more of a Gnats appendage to output power!

Second nasty surprise....

One axis, well it happens but two axies, unforgivable!! A whole new meaning to " on twist "

Cheers Graham.


Online Jasonb

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Re: Two little CHUK's
« Reply #19 on: September 01, 2019, 11:28:30 AM »
That looks like a candidate for the Forest engine with it's helical fins ;)

I also went with the CI valve, easy enough to part off and good for Jo's figure too as she won't have to buy those Peking Duck Pringles after all :LittleDevil:

Look forward to seeing what the shutter improvement ism maybe a slight amount of free play in the vertical movement?

Online Jo

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Re: Two little CHUK's
« Reply #20 on: September 01, 2019, 11:29:05 AM »
 :o

We didn't find any problems on our original Cylinder like that. There are a couple of drops on the fins where the Iron didn't flow right, which should turn out.

Jo
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Offline Alyn Foundry

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Re: Two little CHUK's
« Reply #21 on: September 01, 2019, 11:49:16 AM »
Jo,

As you're at the boring stage, you might like to go " large " ?

Because of my association with Chester UK I attended a few exhibitions where I demonstrated their Model
" B " multipurpose lathe. At one event I met Bob Sier who had recently completed a CHUK 1. He said, Graham, make the cylinder bore as large as possible because you get more oomph!

He hadn't used my piston casting as he felt it was too small, this prompted me to make a new pattern, perhaps you have one of the larger diameter castings?

I felt quite proud watching one of my engines running at a show and more so, with who had built it!!

Cheers Graham.

Online Jo

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Re: Two little CHUK's
« Reply #22 on: September 01, 2019, 12:41:42 PM »
Just checked my piston Graham: 40mm at the small end. If I was going to use it I could only go out 1mm or so. The major advantage I can see going large is that it will reduce the wall thickness on the cylinder and take less to heat it up  :thinking: Plenty of time (1/2 a day  ::) ) to think about bore diameter. The other option is to make the fins deeper. I have plenty of 2" CI if we want to go large :naughty:



Using tailstock support the outside of the top of the cylinder has been turned round (but still over sized) to take the fixed steady.  While looking to set up the steady I realised it had been growing mushrooms while in the cupboard  :ShakeHead: So that had to be removed before adjusting the fingers so that they first clamp then backing them off so they support the casting without rubbing too much. A dab of Anti Scuffing Paste doesn't do any harm  ;) And before boring, one thing I often forget is to tighten up the grub screws that clamp the fingers to stop them moving  :facepalm:

With a boring bar sticking a little way out of the holder the end can be faced off square: we don't want any lumpy bits catching the bring bar when we start the bore in anger. Speaking of which a 16mm diameter boring bar looks a bit long and skinny when it is extended out far enough to do the boring  :paranoia:

Jo



 
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Offline Alyn Foundry

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Re: Two little CHUK's
« Reply #23 on: September 01, 2019, 02:07:14 PM »
OK Jo.

Sounds like you have an earlier piston casting then, it's up to you how you proceed.

I'm a little ways ahead of you at this time, it took a little time to clean up the cylinder to become presentable. I'd normally leave the fins " as cast " but had little choice with this one!

We've ground to a halt now, the boring bar hit something on a pass and broke the Carbide tip. My bar is an early Sandvic with " brazed tip " so its over to the forge to repair it.

Cheers Graham.


Online Jo

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Re: Two little CHUK's
« Reply #24 on: September 01, 2019, 02:39:03 PM »
I might take it out to 40mm, which should allow me to use the piston casting, the bottoms of the fins are measuring 48mm so that will leave 4mm walls.

Edit: Just checked the dimension of the bearing stand and 40mm is just on the limit of the internal dimensions for where the vertical part of the support goes up. And it will leave a 5mm wall for some more screws to secure it to the cylinder.

Thinking further this is a vacuum engine so do we want mass to cool the hot air it gulps? Or more fins to disperse the heat? I seem to recall seeing someone playing a flame on the fins of a flame licker to get it running  :headscratch:

Jo 
« Last Edit: September 01, 2019, 02:49:09 PM by Jo »
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Offline b.lindsey

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Re: Two little CHUK's
« Reply #25 on: September 01, 2019, 03:00:41 PM »
They seem to need some heat in the cylinder mass to get going, but then you want to dissipate as much as possible at least for longer run times.

Bill

Offline b.lindsey

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Re: Two little CHUK's
« Reply #26 on: September 01, 2019, 03:04:58 PM »
Have you thought about using a graphite piston at all?

Bill

Online Jasonb

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Re: Two little CHUK's
« Reply #27 on: September 01, 2019, 03:11:25 PM »
Last time I ran Chuky he stated on the second flick of the flywheel from cold.

I have found it picks up a bit as it comes upto running temp but will start to drop off if it gets too hot but playing with flame sizr and position seems to prolong the run time if you don't suck too much heat in.

Offline Alyn Foundry

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Re: Two little CHUK's
« Reply #28 on: September 01, 2019, 03:19:33 PM »
Hi Jo.

Hmmmmmm, I'm glad you mentioned the bearing support yoke.    :)

We might have ended up with a problem, perhaps the new tip can wait. I seem to remember partially machining mine to allow the piston entry into the cylinder. A good call and hopefully in the nick of time!!

Yes these engines rely on a cool cylinder to " condense " the working fluid, heated air. Obviously the heat transferred to the cylinder walls and then dispersed via the finning try's to keep the differential. Ultimately the cylinder gets too hot for them to work properly.

I've never understood why some needed preheating, possibly because the cylinder to piston fit was too close? Or incorrect valve timing?  My engines have always run beautifully from cold and slowed down as the cylinder temperature increased.

With CHUK 2 the cam disc is screwed directly onto the flywheel, inside boss removed. Timing is achieved by rotation with respect to the fixed crank web.

Thanks again for the timely reminder.

Cheers Graham.


Offline Alyn Foundry

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Re: Two little CHUK's
« Reply #29 on: September 01, 2019, 03:43:09 PM »
Big bore, it ain't!!

See photo.

CHUK 1 or 3 for bigger bores.