Author Topic: Two Cylinder Engine  (Read 26207 times)

Offline AlexS

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Re: Two Cylinder Engine
« Reply #240 on: November 27, 2019, 07:40:47 PM »
Maybe a crazy idea. But what about this.

If I am correct, the valve guide was tailor-made to 2.5 mm.
Mount an axle with the same diameter in the valve guide. Just looked that this may be available in silver steel material.
You could possibly mount a valve cutter on this shaft that has the same fit as the shaft. The valve cutter could possibly be clamped in a column drill. And possibly have high speed cut (hoping for few vibrations). With the aim of no rotating movement in the valve guide and possibly better concentric of the valve cutter.

Greets Alex

Offline Roger B

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Re: Two Cylinder Engine
« Reply #241 on: November 28, 2019, 05:32:28 PM »
Thank you Alex  :) The seat cutter was made from the same cap head screws as the valves. I didn't cut the hex off and made some cutting edges with a fine file. It is hand operated to minimise chatter/vibration. After lapping the valves, cleaning and reassembling I checked the seating using air pressure from the manifold side. They all withstood 4 Bar (60psi) from a tyre pump.

There could be many reasons for this failure. The seatings may have been too narrow. Quite a lot of heat is dissipated through the seatings. The valve clearance may have been too small and closed up when the engine was hot so the valves didn't seat. There may have been residual stresses that caused the valve heads to distort slightly  :thinking: I will have to wait for the next opening of the R+D department. Maybe I should keep the revs to 6000-7000?

As I have spent too much time playing with fiddly little pieces I decided to start on the alternative 360░ crankshaft for this engine. ( I am also planning a 25mm bore 25mm stroke version in case I can't reach my desired output). I didn't have any more 30mm ST50 (~EN8) so started with some 35mm bar. Plenty of swarf  :)
Best regards

Roger

Offline doubletop

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Re: Two Cylinder Engine
« Reply #242 on: November 29, 2019, 09:43:39 AM »
Roger

A very nice engine and I like the idea of the PC radiators. My Bobcat was built for water cooling and I just conected it to the tap. I'll be ordering a radiator as soon as I finish typing here

Pete
?To achieve anything in this game, you must be prepared to dabble on the boundary of disaster.? - Stirling Moss

Offline Roger B

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Re: Two Cylinder Engine
« Reply #243 on: December 07, 2019, 07:52:06 AM »
Thank you Pete  :)

The last section was turned down to 30mm leaving a barely detectable line. I clamped the crankshaft blank in the quick set Keats angle plate and used the mill to set out the crankpin centre drilling then back to the lathe to turn the crankpins. This time I remembered to start with the one nearest the tailstock  ::) The cut was quite chattery with the interrupted cut but settled down once the pin was round. I found it best to increase the depth of cut whilst traversing the parting tool so I was only loading the corner not the full width. Doing this I could increase the cut 0.1mm per traverse. When I got down to 8.5mm I faced the webs with a 8mm tool.
Best regards

Roger

Offline Roger B

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Re: Two Cylinder Engine
« Reply #244 on: December 07, 2019, 07:57:24 AM »
Finally I set the parting tool square and finished the journals 8mm diameter ready for a final polish. As expected when I released the tailstock centre the end of the crank moved about 0.5mm due to the unbalanced stresses. I will finish the rest of the machining and then carefully straighten it. The 180░ crank didn't have this problem as the stresses were fairly well balanced.
Best regards

Roger

Online Kim

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Re: Two Cylinder Engine
« Reply #245 on: December 07, 2019, 06:49:32 PM »
Very nice, Roger!  Regarding the warping, I'm unfamiliar with the European naming for the steel. You said you're using EN8, but is that 'stress proof'?  Like the 1144 Stressproof steel we can get in the US?  Or is it just standard steel?

Also, what's the clearance problem you're referring to in image "645 Clearance problem.JPG"?   is it the clearance between the workpiece and the SHCS clamping the compound slide?  Or something else?

Thanks,
Kim
« Last Edit: December 08, 2019, 03:41:58 PM by Kim »

Offline Roger B

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Re: Two Cylinder Engine
« Reply #246 on: December 08, 2019, 08:09:56 AM »
Thank you Kim  :) I'm not really sure of the equivalence. ST50 is a medium carbon construction steel, nothing special may be similar to 1040. It is cold rolled so tends to have built in stresses and it will warp if the metal removal is not balanced. You are correct there was a clearance problem with the cap head screws so I had to increase the tool overhang even more.

The next stage was to finish the ends of the shaft. This was done in a series of steps to try and keep everything as rigid as possible. Luckily the tailstock centre kept it true so I didn't need to put spacers between the webs. It even ended up looking like the drawing  :)

I now need to decide how to balance it. I may just remove material from the centre web and leave the two ends round  :thinking:
Best regards

Roger

Offline Brian Rupnow

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Re: Two Cylinder Engine
« Reply #247 on: December 08, 2019, 11:57:48 AM »
Roger--That's a great looking crankshaft. 1144 stress proof is only available in round bars in Canada. I always mill away two sides so that I have a piece of "flat-bar" to work with, which is  a lot of extra work. I think by doing it the way you have is going to leave far too much "counterweight".  Let us know please, Brian.

Offline Admiral_dk

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Re: Two Cylinder Engine
« Reply #248 on: December 08, 2019, 04:44:07 PM »
Nice looking crank Roger  :ThumbsUp:

Brian - there is no counterweight right now ...!!... for that to happen, Roger will have to remove weight from the same side as the crank "pins" ...!

Offline Roger B

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Re: Two Cylinder Engine
« Reply #249 on: December 08, 2019, 06:40:39 PM »
Brian, Per is right there. The 180░ crank that is currently in the engine is made the same way but that is inherently statically balanced. For this one I need to remove enough metal around the crankpins to compensate for the mass of the crankpins, big ends and some percentage (always a discussion point) of the mass of the conrods and pistons. Leaving the crankshaft round will increase the total mass of the engine but unless you are intending to fly it does it really matter. It certainly reduces the machining.

I am sorting out a few other bits and pieces. I feel that this engine needs a silencer to avoid problems with the neighbours and have started building one based on the one on the horizontal engine. Following the advice on various threads I decided to purchase some 3mm spotting drills to use rather than the centre drills. They seem to work  :)  Silver soldering the baffles in place was fun but ended up ok. I am waiting for a length of 7mm brass pipe to finish this off. I also wondered if the limited output was due to a mismatch of the generator and engine and purchased another motor to use as a generator. This is the same frame size as the one I am using on the horizontal engine but has a different winding. The 'model' couplings in this size all seemed expensive but I found a small Fenner coupling with 6mm pilot bores that would suit and is good for 17 000 rpm  ::) The motor end was opened out with a previously made 1/4" reamer. The engine end was drilled out 9mm and then bored to 10mm to avoid the deflection caused by the grub screw hole. When assembled the motor is quite capable of cranking the engine with a 12V battery  :)
Best regards

Roger

Offline Roger B

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Re: Two Cylinder Engine
« Reply #250 on: December 09, 2019, 05:58:19 PM »
I finally received the smaller radiators but they didn't have a place for a filler/vent. I carefully drilled a 3mm hole in the end of the header tank and opened it out with a taper reamer until I could start an M8x1 tap. A small adaptor was turned up and threaded to suit. This was then screwed in place with the aid of some two component epoxy putty that is rated for 120░C (I have already been caught out by the low temperature rating of Rapid Araldite  ::) )

The piece of 7mm brass tube arrived so I could finish the silencer. I had a brief test run (too dark for photos or videos  :( ). The silencer significantly reduces the crackle and I got about 80W (9A at 9V)  :whoohoo:
Best regards

Roger

Offline AlexS

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Re: Two Cylinder Engine
« Reply #251 on: December 10, 2019, 06:42:52 PM »
Nicely done. Great job, done alot :ThumbsUp:

Offline Ye-Ole Steam Dude

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Re: Two Cylinder Engine
« Reply #252 on: December 10, 2019, 08:17:25 PM »
Hello Roger,

Super nice radiator that will look great with your setup.

Have a great day,
Thomas