Author Topic: Two little CHUK's  (Read 7969 times)

Offline Jo

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Re: Two little CHUK's
« Reply #75 on: September 08, 2019, 04:01:51 PM »
Join the gang: I have costrochondritis but today it has been compounded by the arrival of giant Hun-Yuns.  :paranoia:


Why is it that every time I hear someone else has Pleurisy I am reminded of the pleurisy joke on I'm sorry I haven't a clue..Why is it that every time I hear someone else has Pleurisy I am reminded of the plural-I-say joke on I'm sorry I haven't a clue  :slap:


Jo
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P.S. Rumour has it that these Hun-Yuns have the potential to contribute to global warming   :o

P.S.s For those of you who know nothing of the great british institution of I'm sorry I haven't a clue, some of the best games are on this page: https://www.bbc.co.uk/programmes/articles/4pfSTqkKVLNyVfr8MjPyRy0/the-five-funniest-games-from-im-sorry-i-havent-a-clue I am not sure if it will work outside the UK  :noidea:
Enjoyment is more important than achievement.

Offline Jo

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Re: Two little CHUK's
« Reply #76 on: September 08, 2019, 04:53:11 PM »
Having faced off the surface I discovered its a long way down milling that slot  :paranoia:  Thankfully I had drilled either end before starting which made life easier.

It was not possible to get the measurement on the drawings from the bore to the valve port face as the casting was already below that measurement so it was necessary to mill a bit off the base so that it was a nat's whisker below the valve port face distance.

Having sorted out my thoughts on the mounting of the bearing yoke it could then be bored. You can see how close 40mm is on the vertical - it just scrapes. The final bit that needed milling was the stand for the bearing block, which once machined I had the working dimensions for the block itself, which was a simple boring exercise.


Family shot: The bearing yoke and base have also been attached to the cylinder  :)

Jo
Enjoyment is more important than achievement.

Offline Alyn Foundry

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Re: Two little CHUK's
« Reply #77 on: September 08, 2019, 07:05:02 PM »
Blimey Jo....  :o

You're way ahead now!!

I think it's time I let you know about an improvement that was tried on CHUK 4. This engine is still not finished, but the idea is sound.

Instead of the cam pushing against a roller and spring to operate the shutter CHUK 4 lifts the roller that is mounted to some 1mm by 15mm Flat Ground Stock. This has a 10 mm slot milled lengthwise ( Scotch yoke like ) and uses the crankshaft as a guide. The improvement lies in the fact that a compression spring isn't there to sap energy from the system.

The choice is yours however Jo, but that's what I'll be doing.

I'd suggest using small precision ball races for the roller, big end and gudgeon pin as it makes quite a difference to the overall output power that's pretty low from the start.

Almost the home straight in sight Jo, pretty sure you'll win.

Cheers Graham.

Offline Jasonb

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Re: Two little CHUK's
« Reply #78 on: September 08, 2019, 07:16:08 PM »
Graham, I assume you would go for bearings without seals or remove the rubber seals if they have them to keep drag to a minimum.
« Last Edit: September 08, 2019, 07:21:21 PM by Jasonb »

Offline Alyn Foundry

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Re: Two little CHUK's
« Reply #79 on: September 08, 2019, 07:32:55 PM »
Graham, I assume you would go for bearings without seals or remove the rubber seals if they have them to keep drag to a minimum.

I never got around to a casting for the main bearings, Jo's solution looks fine.

Yes I'd suggest removing the inner seal of each and perhaps fit an " ornate " polished  Brass oil cup to finish. By replacing the grease with a light oil would definitely reduce drag however I never tried it myself.

As for the rollers, I wouldn't worry about those.

Offline Jo

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Re: Two little CHUK's
« Reply #80 on: September 09, 2019, 07:40:30 AM »
Instead of the cam pushing against a roller and spring to operate the shutter CHUK 4 lifts the roller that is mounted to some 1mm by 15mm Flat Ground Stock. This has a 10 mm slot milled lengthwise ( Scotch yoke like ) and uses the crankshaft as a guide. The improvement lies in the fact that a compression spring isn't there to sap energy from the system.

I had been thinking about a pull rather that a push shutter mechanism: I would like it to have a look/feel more like the original Planck mechanism and have been reviewing some other Flammenfresser designs but none were a inverted engine :noidea:

Jo
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Offline Bluechip

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Re: Two little CHUK's
« Reply #81 on: September 09, 2019, 09:03:51 AM »

P.S. Rumour has it that these Hun-Yuns have the potential to contribute to global warming   :o



Indeed they do ........  :embarassed:  :embarassed:  :embarassed:

Anon.

Offline Jasonb

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Re: Two little CHUK's
« Reply #82 on: September 09, 2019, 09:21:03 AM »
Are they not carbon neutral having taken in all that CO2 while growing before the methane gets produced

Offline Alyn Foundry

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Re: Two little CHUK's
« Reply #83 on: September 09, 2019, 11:38:32 AM »

 but none were a inverted engine :noidea:

Jo

As I've stated many times, I have a " thing " for inverted engines Jo, look at my Avatar. CHUK 2 is a
" ME " engine.

Ultimately the choice is yours, the compression spring offers little resistance to the overall running.

My friend Mike Rodgers from Nantwich had several cam discs produced via the relatively new CNC process, where the profile was milled as a slot. A small roller was made to follow the slot, we called it a " Desmo " drive. He nearly died when he went to pick up the finished parts, never got a price, nigh on 200.00 for 10 cams. A small fortune 20+ years ago! Backyard stuff these days.

I'll be back with you when I can.

Offline Jasonb

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Re: Two little CHUK's
« Reply #84 on: September 09, 2019, 01:09:33 PM »
The slot option sounds good Graham, I was wondering how the lifted shutter would close again if there was no spring to pull it back down onto the cam. Jo you can send me a drawing if you want a CNC groove

For the scotch yoke option is the horizontal slot larger than the pin to give some time where the shutter is stationary much like you had on Nattie

Offline Alyn Foundry

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Re: Two little CHUK's
« Reply #85 on: September 09, 2019, 04:05:38 PM »
The slot option sounds good Graham, I was wondering how the lifted shutter would close again if there was no spring to pull it back down onto the cam. Jo you can send me a drawing if you want a CNC groove

For the scotch yoke option is the horizontal slot larger than the pin to give some time where the shutter is stationary much like you had on Nattie

Ah, but there's no need for a slotted cam on CHUK 2 Jason. We have good old gravity acting for us, the mass of linkage, shutter and roller all help to reclose the port as the cam rotates.

I'm wondering if my term " Scotch yoke " is perhaps a little misleading here? I'll try and get out to the workshop and grab one to photograph.

Cheers Graham.

Offline Jasonb

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Re: Two little CHUK's
« Reply #86 on: September 09, 2019, 04:19:51 PM »
Graham, if you mean that the slot is vertical to go around the crankshaft and keep the rod vertical then I know what you mean. Very similar to this arrangement on my RMC engine except the pin or roller would be on the left of the crankshaft to lift it rather than as shown on the right where it is pushed down.

You can stay in the warm now ;)




Offline Jasonb

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Re: Two little CHUK's
« Reply #87 on: September 09, 2019, 04:34:24 PM »
Or even this

Offline Alyn Foundry

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Re: Two little CHUK's
« Reply #88 on: September 09, 2019, 06:58:51 PM »
Or even this

LOL

That's exactly what I meant Jason, spot on.. :ThumbsUp:


Offline Jasonb

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Re: Two little CHUK's
« Reply #89 on: September 09, 2019, 07:02:58 PM »
So the next question is will the shape of the cam need altering?

That cam would have held the shutter down for longer when pushing but will hold it up for longer now it is lifting.