Author Topic: Digger  (Read 3496 times)

Offline Jasonb

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Re: Digger
« Reply #30 on: October 11, 2023, 08:23:02 PM »
The other end cylinder cover was faced and turned to diameter and the spigot formed to fit the cylinder before transfering to the mill where the face mill was used to bring the block for the valve rod bracket down to final height.



Then a 6mm cutter with 1mm convex corner radius was used to both size the block and face the rest of the cover down to 3/32" thickness leaving a nice internal fillet.



Finally the six stud holes were drilled 2.5mm and the two that secure the pivot tapped M2.5



The drawings call for the trunions to be fabricated from a flat piece of brass and some stainless rod. I started out with two pieces of 8mm dia 303 stainless and reduced a suitable length down to 7mm and added a deep ctr to the ends and part drilled 1/8" dia. Two oversize rectangles of 1/4" thick brass were drilled 7mm and then silver soldered to the stainless rods. Once cool They were held by the remaining 8mm dia so that the face of the brass could be turned true to the shaft and a light skim taken off the 7mm dia just to clean it up.



After sawing off from the 8mm bar the inner faces were machined along with the spigot to locate into the holes in the side of the cylinder



Here I have used the cylinder to gauge a firm fit of the two parts as I don't want them to loose there positions when taken apart after the final insitue machining.



After this the rectangle was milled to the final overall size and the mounting holes drilled



The cylinder and it's trunions were then assembled with temporary cap head screws so that the trunion shafts could be turned to final 1/4 "diameter between ctrs. I almost came a cropper here as it was difficult to get any turning tools in without either hitting teh tailstock ctr or catching the scre wheads, In the end I manage dwith a home made 6mm dia dead ctr held in an ER16 Collet chuck to support the work and a  boring bar and bit to do the actual turning.










Online Dave Otto

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Re: Digger
« Reply #31 on: October 12, 2023, 12:17:29 AM »
Lots of interesting setups and and nice machine work.  :ThumbsUp:

Dave

Offline Jasonb

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Re: Digger
« Reply #32 on: October 13, 2023, 07:50:09 PM »
The drawings call for the two crank webs and pin to be machined from a supplied short piece of 1" x 1/2" steel flat with the two shafts held into the webs with epoxy. I did not like the sound of this so decided to use the more common way of slipping the two webs onto a single shaft and a short pin, all held together with 648 Loctite and pinned for good measure. I used the CNC to do the basic oval shape of the webs and the raised boss on one side but then transferred to the manual mill to ream the two holes in each and then the lathe to do the shorter round boss on the opposite side with teh web mounted on an arbor.



Not the best focus but hopefully you can see one pin and not the other that has been filed flush



Five spoke flywheels are never the easiest to hold by the inside of the rim as neither a 3-jaw or 4-jaw chuck seems to have the jaws in a position to miss all he spokes so I took the option of using the 4-jaw to hold by the minimum amount of the OD while one side was faced and as much as the OD turned (a little over diameter) as possible.



Swapping the the 3-jaw I completed the OD, opposite face and hub before reaming the bore 1/4". I also tidied up the inside of the rim with a 6mm round insert. After painting the flywheel can be mounte donto the previously used 1/4" mandrel and the OD and sides of the rim skimmed to both blend the two cuts on the OD and remove any stray paint at the same time. Drawing says to fix the flywheel to the crankshaft with epoxy but I went with an M3 grub screw bearing onto a small flat to protect the shaft.



That completes the machining and here are a couple of slightly out of sequence shots of the almost completed engine. I test ran it like this with just cap heads and no gland packing and all seems good so I'll post again soon with some images and video of the painted engine complete with nuts and studs in place of the cap heads.






Offline Dalboy

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Re: Digger
« Reply #33 on: October 13, 2023, 08:08:34 PM »
That is one nice engine I do like the flywheel will it all be painted as it looks nice as it is

Offline Jasonb

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Re: Digger
« Reply #34 on: October 13, 2023, 08:21:27 PM »
Thanks, only the cast surfaces will be painted plus the gland boss on the cylinder cover as that has a casting flaw. As shown in the attached screen shot of the CAD model. It will be satin black.

I meant to add that I also machined the two end and central concave edges of the bases with a boring head as the last bit of machining, sorry no picture.

Offline Jasonb

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Re: Digger
« Reply #35 on: October 16, 2023, 06:44:28 PM »
To finish of this thread here  are some pictures and a video of the finished engine. As I said a bit more bright metal than I would personally go for but quite happy with how it looks, the satin black sets off the bright metal well which is almost all straight off the machine no additional buffing or polishing except the flywheel rim and rear cylinder cover that got a bit of emery.

I'm still none the wiser as to why they called it "Digger" If I get round to making my own I think it will be called "Shaker" as the cylinder reminds me of a cocktail shaker not because it jumps about even at speed - all that heavy bronze keeps it quite firmly planted.











<a href="https://www.youtube.com/watch?v=YBbB2WvekKo" target="_blank">http://www.youtube.com/watch?v=YBbB2WvekKo</a>

Offline crueby

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Re: Digger
« Reply #36 on: October 16, 2023, 06:51:28 PM »
Thats gorgeous!!   :ThumbsUp: :ThumbsUp:

Online Kim

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Re: Digger
« Reply #37 on: October 16, 2023, 06:52:41 PM »
Beautiful little engine, Jason!  :popcorn:  :ThumbsUp: :popcorn:

Kim

Offline Admiral_dk

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Re: Digger
« Reply #38 on: October 16, 2023, 09:47:17 PM »
Beautiful and smmoth runner  :praise2:

The Customer should be very pleased with the end result.

Per   :cheers:

Online Dave Otto

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Re: Digger
« Reply #39 on: October 16, 2023, 09:51:05 PM »
Very nice!

Dave

Offline MJM460

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Re: Digger
« Reply #40 on: October 16, 2023, 11:29:57 PM »
An interesting and different engine, beautifully done.

Thanks for presenting it Jason.

MJM460
The more I learn, the more I find that I still have to learn!

Offline Krypto

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Re: Digger
« Reply #41 on: October 18, 2023, 12:58:46 AM »
Wow, that gunmetal makes a beautiful set of castings! Expert job on machining and the paint/finish job is just out of the park!

I wish something similar to this kit was still available.
My Workshop Blog:  https://doug.sdf.org/

Offline Dalboy

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Re: Digger
« Reply #42 on: October 18, 2023, 06:20:26 PM »
The way you have painted the engine really shows it off to its best. Lovely job all round :ThumbsUp:

Offline RReid

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Re: Digger
« Reply #43 on: October 23, 2023, 03:17:08 PM »
That's a lovely little engine, Jason, in both looks and running quality!
Regards,
Ron

 

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