Author Topic: Another breath engine (Huff and Puff)  (Read 3114 times)

Offline b.lindsey

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Re: Another breath engine (Huff and Puff)
« Reply #15 on: April 20, 2019, 01:53:27 PM »
Moving right along Roger. The conrod looks great but really small as Roger said. I love it!!

Bill

Online Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #16 on: April 21, 2019, 12:45:44 PM »
Thank you Bill, I think you mean Per  :)

The piston was finished to size, but what is a snug fit? It's different for a fuel injection component or a breath engine. After I had turned the cylinder cover I tried to quantify this. Dry the piston fell straight through and with the cover in place it fell in a few seconds.


With a drop of light oil the piston just sat there with or without the cover  ::) Obviously what the comments about lubrication being a problem meant  :thinking:

I then started on the flywheel and excentric. I have decided I will try and cut the recesses in the flywheel with a 4mm end mill on the RT rather than attempting to make a small trepanning tool. The next steps for the excentric are also on the mill so time to change modes again.
Best regards

Roger

Online Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #17 on: May 01, 2019, 11:33:53 AM »
The flywheel was centred in the Proxxon RT and the recesses were milled with a 3mm end mill, plunging in the middle and then finishing to 4mm with 0.5mm cuts either side. The back of the excentric was milled to size with the RT set vertical. The RT was then moved to the Proxxon drill to drill the bore 0.4mm and ream 1.5mm. The RT was then set vertical again to drill and tap for the M1.4 fixing screw. Finally the flywheel was set at 30 in the normal vice for drilling and tapping M1.4. The hole position was initially flattened with a 1mm end mill so the tapping drill did not wander.
Best regards

Roger

Offline gbritnell

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Re: Another breath engine (Huff and Puff)
« Reply #18 on: May 01, 2019, 12:14:30 PM »
Roger, you're a courageous fellow tapping a M1.0 hole like that.
Nice work.
gbritnell
Talent unshared is talent wasted.

Online Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #19 on: May 01, 2019, 05:37:59 PM »
Thank you George  :ThumbsUp: Not quite so brave, it's M1.4, and I find the little Proxxon drill makes a good tapping stand if you remove the drive belt.

As the little drill was set up the next stage was to drill the ports in the cylinder. It was set at 45 using a V block, the edge was found and the cylinder was traversed 0.65mm (half the port diameter). I started with a 1mm end mill followed by a 0.8 mm centre drill and finally a 1.3mm drill (all at 4700 rpm). This was repeated for the other port.

Back to the lathe to part off the excentric. This was then mounted on a piece of 1.5mm silver steel and the little spacer piece was machined on the front followed by facing the parting pip off the back. The flywheel was then clamped on the same stub using the tailstock centre and given a quick deburr/polish. The chuck was then changed to the 4 jaw SC to finish the inlet stub on the cylinder. Next step mill out the frame.

This engine is quite a challenge to work out the correct machining sequence so you don't remove a piece you need to hold for the next operation  :headscratch:
Best regards

Roger

Online Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #20 on: May 02, 2019, 07:46:34 PM »
I took the bulk of the material out of the frame with a 10mm end mill. Unfortunately my 4mm ball nose mill was slightly too short so I had to tilt the frame to round the fillets. With the middle cut out I could drill the cylinder fixing holes and then move on to finishing the main bearing stands. I will leave the stands at full height until I have finished the main bearing holes to allow for easier location.
Best regards

Roger

Online Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #21 on: May 05, 2019, 08:44:08 AM »
The main bearings were drilled 1.4mm and reamed 1.5mm. I decided it would be quickest to remove the rest of the frame with a hacksaw and then clean it up in the mill. Leaving the main bearing stands at full height made it easy to hold. Next I milled the inlet/valve area of the cylinder down to 6mm. I will have to decide whether to radius or chamfer the corners of the cylinder (probably once I know it works  ::) ). To complete the required machining of the base I milled the 6mm clearance slot for the flywheel.
Best regards

Roger

Offline b.lindsey

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Re: Another breath engine (Huff and Puff)
« Reply #22 on: May 05, 2019, 02:32:22 PM »
Am enjoying all the pictures Roger. Lots of work in that little frame!!

Bill

Online Kim

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Re: Another breath engine (Huff and Puff)
« Reply #23 on: May 05, 2019, 03:27:05 PM »
Nice work Roger!  That is just a lot of itty-bitty-little machining you're doing there :)  :popcorn:
Kim

Online Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #24 on: May 05, 2019, 08:26:52 PM »
Thank you both  :)  :) I'm never sure if I post too many pictures of each machining step  :headscratch: I know I like to see how others set up to machine things and the set ups they use.

The next step was the cylinder fixings. I drilled the 3 holes in the cylinder cover using the Proxxon RT and then spotted all the hole onto the cylinder. Unfortunately I broke the plug tap in one of the cover holes  :facepalm: I took a quick family shot before putting the cylinder in the alum solution.

While this takes place I moved onto a few other bits. I was able to get some  M1.4 x 6mm cap head screws which are fine for the cylinder fixing but too long for the cover. I also need a couple of M1.4 grub screws for the flywheel and excentric. I tapped a piece of 4mm square silver steel M1.4 and then milled a 0.6 mm step 0.2 mm over the centre line. After hardening I cut the screw down to 3mm and the used the guide to cut a slot for the grub screw using an Xacto razor saw with a 0.4mm wide blade.
Best regards

Roger

Online Kim

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Re: Another breath engine (Huff and Puff)
« Reply #25 on: May 06, 2019, 05:14:35 AM »
Sorry about the broken tap  :'(   I certainly feel your pain there.  Hopefully the alum will work for you.
Kim

Online Jo

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Re: Another breath engine (Huff and Puff)
« Reply #26 on: May 06, 2019, 03:11:31 PM »
I'm never sure if I post too many pictures of each machining step  :headscratch: I know I like to see how others set up to machine things and the set ups they use.

I like to see other people's set ups as well: You can always learn something new or an easier variation of how to do something than you normally use :ThumbsUp: When Vixen visited on Friday we were talking and he likes the technical discussions about the engines and their history and is less interested in the step by step stuff. But then again we did sit chatting for a few hours on how to set up to machine his Propeller hub  :noidea:


Bummer about the tap  :(

Jo
Usus est optimum magister

Online Vixen

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Re: Another breath engine (Huff and Puff)
« Reply #27 on: May 06, 2019, 06:22:35 PM »
I'm never sure if I post too many pictures of each machining step  :headscratch: I know I like to see how others set up to machine things and the set ups they use.

It is always interesting to see other peoples set-ups and the special techniques they use. That's how we all learn. As Jo said, we spend a long time discussing the merits of various ways and set-ups to machine the tapered spline in the Jupiter's propeller hub. Hopefully there will be one that's works better than the rest.

I am also interested in how you use the alum to remove the broken tap. I have tried to do it in the past but without success. I seems that the word alum means different things in different places and not all work at dissolving broken taps or drills.

Please can someone identify the type of alum which works and where to buy it from.

Thanks

Mike

It is the journey that matters, not the destination

Offline Florian Eberhard

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Re: Another breath engine (Huff and Puff)
« Reply #28 on: May 06, 2019, 06:48:20 PM »
I took a quick family shot before putting the cylinder in the alum solution.

Hi Roger

In Case the alumn doesn't work, you can still try sulphuric acid. Thats what I used for removing a broken drill from my cochran boiler and that worked pretty well!
(Look here, answer #137: http://www.modelenginemaker.com/index.php/topic,5740.135.html )

Online Roger B

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Re: Another breath engine (Huff and Puff)
« Reply #29 on: May 06, 2019, 07:38:11 PM »
Thank you all for the interest  :ThumbsUp:

Alum (I will get the exact formula tomorrow when I am at work as that's where I got mine from) does work but you have to use it at a fairly high temperature ~80C. I was able to remove a broken HSS tap from an aluminium conrod previously, the current tap is reducing in size but it takes time. As far as I know it won't touch Tungsten Carbide (for those who use expensive taps).

I have made a few other small pieces with the Proxxon FD 150, the crankshaft, clevis pins for the piston rod and valve and the blank for the valve. Next step is back to the Proxxon mill to finish the valve and excentric rod. I did think about redesigning the excentric rod to give an adjusting screw but hopefully it won't be needed.

The clevis pins and rings are kept in a plastic bag as one sneeze and they are gone  ::)
Best regards

Roger