Author Topic: Little Wall  (Read 2400 times)

Offline Johnmcc69

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Re: Little Wall
« Reply #30 on: April 26, 2022, 05:50:22 PM »
 :ThumbsUp:
It's a shame that the crank will be hidden inside, that turned out beautifully!

 John

Offline Jasonb

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Re: Little Wall
« Reply #31 on: May 01, 2022, 04:46:28 PM »
Indeed it is, maybe that is why I prefer the open crank IC or steam engines where you can see a bit more of what is going on.

I did not take many photos of the flywheel being made as the process was very similar to others I have done. Basically a slice of cast iron bar was turned and bored undersize, some waste material removed on the manual mill before cutting the spokes on the CNC.



I also turned up the pulley for the starter cord and then it was safe to set over the topslide so all the tapers could be cut without disturbing it. First the two ends of the crankshaft were done.



Then the two bores. As the taper got smaller towards the headstock and the topslide was advancing the opposite way I needed to cut on the back side of the bore I needed to use  one flute of a 3 flute cutter held in the topslide which worked well fiving a taper from 8mm down to approx 7mm with a little room to spare around the 6mm dia cutter. Here you can see me gauging the size using a park on the crankshaft to get the right length of taper into the hole.



The piston was straight forward turning but I did use the CNC to form the dog bone recess in the underside as well as the shaped top, a flange type ER32 collet chuck comes in useful for these types of jobs and does nor damage or mark the thin skirt of the piston



A group shot of progress at this stage. There is also a Tufnol disc which clamps around the end of the exposed main bearing and that carries one of the ignition contacts, rotating the disc advances or retards the timing.




Offline RReid

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Re: Little Wall
« Reply #32 on: May 01, 2022, 05:29:57 PM »
Continuing to enjoy this build, Jason. That is a pretty little piston!
Regards,
Ron

Offline Zephyrin

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Re: Little Wall
« Reply #33 on: May 01, 2022, 08:16:27 PM »
Nice piston with the deflector, true vintage model !
the transfer does not seems to be piston ported ?

Offline Jasonb

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Re: Little Wall
« Reply #34 on: May 01, 2022, 08:37:24 PM »
Here's a couple of extracts from the original drawings showing the ports

Offline Jasonb

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Re: Little Wall
« Reply #35 on: May 07, 2022, 04:40:37 PM »
The carb design for this engine is quite similar to that of the Stuart Lightweight I made some time ago and I took the same approach of silver soldering a bunch of brass parts together to replicate the casting all done on the manual machines. I did however make use of the CNC to shape the fuel bulb, first roughing it out with an adaptive cut - the inside has a shallow draft angle.



And then a finishing path to tidy things up



While still in the vice the two lugs were drilled and tapped M1.6 and then used to hold the previously turned cover which was nounted upsid edown so as not to crash the cutter into it's threaded spigot. Again a roughing and then a finishing pass were used.



Here are all the parts prior to soldering the body together



Once soldered the body could be treated much like a casting and the various remaining hole sand passages added, here the throttle body is being drilled prior to reaming.



And the completed carb in bits and all assembled





I'm not one for silencers so a simple stub pipe exhaust was bent up from 8mm copper tube and silver soldered to the flange



Finally a quick trial fit on the manifold




Offline Alyn Foundry

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Re: Little Wall
« Reply #36 on: May 07, 2022, 05:39:30 PM »
Very nice work Jason. :ThumbsUp:

I can see something else that is nearing completion too !  ;)

 :cheers: Graham.

Offline Admiral_dk

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Re: Little Wall
« Reply #37 on: May 07, 2022, 06:36:31 PM »
Looks amazing Jason  :ThumbsUp: - did you use a jig to hold all the parts in place while soldering ?

Per

Offline Jasonb

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Re: Little Wall
« Reply #38 on: May 07, 2022, 06:54:00 PM »

Graham, that one has stalled a bit.

Per, I made it so it held itself together. You can see a rod coming out of the fuel bowl, that passes through several parts and had a nut on the end to pull them together and the slots keep them lined up. This rod got machined away as the passages were drilled

The angled boss for the needle fits into a hole and that in turn stops the throttle barrel sliding down too far. Finally the flange fits onto a spigot on the top of the vertical part, I left the flange round and shaped it after soldering so did not have to worry if it revolved during soldering.

I think I just wired on the small tab that the throttle lever stops bear against

Offline Jasonb

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Re: Little Wall
« Reply #39 on: May 18, 2022, 04:58:29 PM »
The conrod started out as a piece of round 2014 rod and was "squared up" on the manual mill using a facemill.



I then narrowed down the big end using the same cutter before holding the rod on end to drill and tap for the big end fixings and then used a slitting saw to cut off the cap.



I then drilled and reamed the two holes followed by milling away some of the waste so that the big end bolts could be fitted, I have then screwed in from the rod side not the cap side. Two top hat bushes were turned up so I could screw the rod to a piece of scrap and then mill to shape on the CNC.






Well that's about all the photos and video I took while making the engine. I finished it off with some Blue VHT and and black Thermacure paint with the crankcase and manifold left in the bear bead blasted finish.















Well at this point you will all be expecting a video of the engine running but it is not obliging. I can't get a decent run out of it and by the time I have picked up the video it's already dead or dying. I know some say it's all about the journey which has been quite a fun one and I also learned a lot about the CNC but can't help feeling the journey is not really complete if you don't make it to the intended destination. Once the blisters from pulling the starter cord have healed I may have another go and make an adaptor to try a RC carb but more than likely it is destined to be eye candy on the shelf.


Offline Admiral_dk

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Re: Little Wall
« Reply #40 on: May 18, 2022, 08:27:14 PM »
That is a shame and I do understand your frustration - looks really good though ....

Do you have any idea if the 'original back then' was known as a runner ?  Or could that be a reason it kind of disappeared into oblivion ....  :noidea:

Per

Offline Jasonb

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Re: Little Wall
« Reply #41 on: May 19, 2022, 07:33:57 AM »
I don't know if the original ran and have not been able to find any examples on the ned dead or alive. Though a bit of googling last night may lead to something, I'll post here if anything comes of it.

Offline Zephyrin

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Re: Little Wall
« Reply #42 on: May 19, 2022, 08:21:47 AM »
Wow, the finish is outstanding, up to the screws and studs...
2 strokes are sometimes temperamental...and yes this is frustrating
may be you are too impatient, it simply requires a break-in !
« Last Edit: May 19, 2022, 08:40:28 AM by Zephyrin »