80cc DOHC V8

[LongRat]

Excellent Pat, love that crank idea.
To countersink the holes, you could make a countersink tool with a thin shank, that is thin enough to fit through the hole in the opposite web half. Tricky operation though. Or maybe something like a small dovetail cutter inserted in from behind the countersink. The design of the crank would seem to remove many of the difficulties of a normal crank, living with the countersink issue would surely be a small price to pay.

 

[aussie bruce]

Hi there Pat

Hmm i love your build and have duly subscribed, could you let me know please where you got your plans from? i would love to buy a copy myself as i would love to do a build of a v8 after completion of my Pisces II flash steam engine.

Your solid works model of the crank looks do able have you considered getting a counter bore / sink drill ground up? i usually get them done for work they cost about 60 dollars Aus at the moment they are available off the shelf from iscar but start at 10 mm dia

For my pistons i have always counterbored the under side and made up a mandrel with a screwed bolt the a dummy gudgeon pin fits through that way i can set the mandrel true screw the piston blank on and then finish turn groove for rings and finish machine the height in one setting

All the best mate from wet old Melbourne

Bruce

 

[pat1967]

Jeroen, Longrat, Bruce

Thanks guys, I'm glad it provided some ideas for you, and you are more than welcome to use it if you like. I did think about making up a custom counter sinking tool with a shaft that screwed into the head. It'd be a bit messy, but would allow assembly in situ and would probably get the job done. Once bored it could be unscrewed and released out.

If I can't pull off the solid crank, I might have to revist it. I plan on machining the crank up before the block, so if it doesn't work out, I'll still be in a position to recover gracefully and save scraping the block.

Thanks for the insight on how you make up your pistons. If you're interested in the Schilling plans, I got mine through VTH in Germany http://www.vth.de/shop/warenkorb/ar...137b378933b11d89908d640.html?cHash=8407db4a24 the plans are a little different from the picture they show. The plans use gears for the valve train, and a kind of primitive fuel injection. I also bought the book through "abe books" http://www.abebooks.com/servlet/SearchResults?isbn=3881801332&sts=t&x=67&y=12

Pat

 

[pat1967]

Spent some time today lightening up the piston blanks, 4 out of the 8 are done and with it getting late and no mishaps I decided to quit while I was still smiling.

Setup was a transfer to the collet chuck on the lathe to drill a pilot hole for the start of the end mill, and provide a centre reference. I had to doctor a 3mm carbide end mill by grinding a relief above the top of the flutes, since they were 12mm and a needed to go 13.5mm deep into the piston and the shank is actually 1/8".

The blank was mounted in the machine vice, using two HSS bits, up against the reliefs previously cut, and a packing ring below to bring the bottom of the piston above the vice jaws. All went to plan, and will aim to hollow out the remaining 4 by the end of the week.

Pat

 

[aussie bruce]

Thanks for those links Pat looks like i will have to hit the placky card next payday. :big: I have been puzzling over your issue with the crank looking at your model of the crank the image you posted drawn in solid works it would be nigh on impossible to machine those inner webs on the crank is the original design meant to run needle roller big ends? using case hardened linear shaft material? Could you post or email me a pack and go of the solidworks model i usually get an hour for lunch to fiddle with this stuff so maybe able to help.

Bruce

 

[LongRat]

I just received my copy of the book by Schillings. What a bargain it is, worth the price simply for the pictures and drawings. It looks to be very nice and detailed with some very nice ideas and in general, a 'modern' feel. Looks like he strives to use rolling-element bearings wherever possible, another thing of which I approve. Anyone who doesn't have this should definitely buy it. Firing up Google Translate now...

 

[pat1967]

Hi Guys,

It's been a while since I've had any progress to post, but managed a few (quite a few) hours in the garage this week, and took the plunge to start lightening up the chunk of 6061 that's to become the cranks case. I had already roughed out the basic V shape and left 0.5mm allowance on the top deck of each bank, just in case.

The machining is all done under CNC on my siege X3.

First set of pics ...

- What its supposed to look like when finished

- Centre drill at 0.5mm and a manual centre witness (the blued area). I elected to make the first outer most bolt hole the zero, in case I had to go back.

- Centre drilled all holes to a comfortable depth

- All pilot holes drilled, and ready for some milling

 

[pat1967]

Now for milling of the water jackets. The recesses are 25mm deep in total, with an 8mm dia bottom fillet. I choose to complete the jackets in 2 stages, the first, routing out the shape with a 6mm endmill to a depth of 21mm leaving me the 4mm to machine the fillet in with a ball nose.

It didn't quite work out as 2, it finished as 3 since the ball nose I had only had a cutting depth of about 20mm and the slot cut by the 6mm endmill was slightly undersize. I offset the ballnose on the Z by +10mm and just re-ran the g-code for the bottoming.

 

[pat1967]

The bit I was dreading, boring the cylinder jackets. I made up a simple plug gauge to the finished bore diameter of 28.00mm, I stepped opposite ends for a short length at 27.90mm and 27.50mm. I fed the boring bar at 0.5mm increments till I got close to the 27.5, then started stepping outward at 0.1 till I got past, but under the 27.9.

The rest of the boring was done at one increment of the boring head dial, then to half increments as I approached the final dimension. You can see the change in chip size from start to finish.

The recess was then finished off with a small clearance in diameter.

 

[pat1967]

bit up cleanup, and a quick wash with some dish detergent, and I'm a happy chappy, it sort of looks like the model

Next will be the cleanup of the underside and pocketing for the crank throws.

Enjoy ... Pat

 

[pat1967]

I just received my copy of the book by Schillings. What a bargain it is, worth the price simply for the pictures and drawings ...

Glad you weren't dissappointed with, way better value than the plans available for the Schillings engines IMHO.

Pat

 

[ozzie46]

That block looks great Pat. I am really enjoying this.

Ron

 

[LongRat]

The block is beautifully finished. Off the meat rack, as we say!
I don't recall reading about the design origins of this engine. Is it your own design, or is it actually from the Schillings plans? I'm not aware of any other plans for a DOHC V8.
I've almost translated the entire Schillings book now. Actually I am wishing it was longer, it is a good read. I have learnt a great deal, but I am a relative model engine novice.

 

[stevehuckss396]

Very nice work!! I can almost hear it running now!

 

[pat1967]

The block is beautifully finished. Off the meat rack, as we say!
I don't recall reading about the design origins of this engine. Is it your own design, or is it actually from the Schillings plans? I'm not aware of any other plans for a DOHC V8.
I've almost translated the entire Schillings book now. Actually I am wishing it was longer, it is a good read. I have learnt a great deal, but I am a relative model engine novice.

Hey longrat,

The design is based on the Schilling's engine, my deviations are ...

- Revised lower crankcase half in 2 parts, so there is a girdle integrating the main cap's and upper sump half, and a lower sump which actually holds the oil.
- Cross plane single piece crank instead of the built up single plane crank
- 4 valves per cylinder in lieu of the 2

Pat

 

[pat1967]

That block looks great Pat. I am really enjoying this.

Ron

Thanks Ron, so far things have mostly gone to plan.

Pat

 

[pat1967]

Very nice work!! I can almost hear it running now!

Thanks Steve, you might be picking up on my "vroom vroom ..." noises I make on the way to work
So far everything has gone well, just finding the time to under take the big tasks like the block has been my issue.

Progress should pick up over the christmas break ... 5 weeks off.

Pat

 

[aussie bruce]

Pat what a lovely bit of work it looks an excellent start mate.

Your cnc X3 lloks like it was well worth the money then do you have a post on it?

Well i am waiting on the arrival from the UK of my book, and after reading all the comments i cant wait to get my greasy mitts on it.

after reading your comments longrat and pat does the book contain the plans for the basic engine? and if you want the plans you buy them separately from the web site link that you posted earlier Pat?

Vroom Vroom its more of a merc or bm sound mate roooooar ;D

Bruce

 

[tonyengines]

Very nice work!! ;D ;D ;D I have made a similar job 2 last years

 

[pat1967]

Pat what a lovely bit of work it looks an excellent start mate.

Your cnc X3 lloks like it was well worth the money then do you have a post on it?

Hi Bruce,

And thanks for the encouragement. I converted my X3 about 4 years back now and took very few photos. I bought the standard X3 from Hare and Forbes, rolled ball screws from "homeshopcnc", angular bearings from vxb, and 425 oz nema 23 steppers from Keling. The bearing blocks and motor mounts I machined using my lathe and X2. I'm very happy with it, for the work I do, mostly aluminium, the only rework I have planned for it is to replace the spindle drive arrangement. 2000 rpm for the small 3mm cutters I normally use, makes for slow shallow feeds.

The Z axis is drive through a timing belt at a reduction of 2:1, X and Y are direct drive using oldham couplers. I tried to find some pics for you, but only have a few showing the bearing and motor mounts assembled.

On the book, I can't say there are complete plans, but there are many photos's and dimensioned section drawings through out it, and various valve layouts etc. The engines shown range from Boxers, Twins, V Twins, and V8's. The only unfortunate thing is the text is entirely in German, but longrat seems to have addressed that.

Pat