Twin Cylinder Build

[Johno1958]

Hi all.
Just started building a twin cylinder sort of loosely designed on Longboy's engines, although already I can tell mine is going to be ugly. It's going to be as simple as I can make it and hopefully it will run.I have bought a slitting saw and boring head for the mill neither of which I have used before so I will learn something maybe. The crankshaft is bolted together through a thin section bearing 17x26x5mm with four m3 bolts ....make that three just broke a tap off in the last hole :wall:not going to get that puppy out but three will hold even two would I think.Just a little rubbing so I have taken a whisker of the back of the webs . Hoping I won't have to use a large flywheel as these webs are thick and heavy 1020 steel .
Cheers
John

 

[Herbiev]

I'll be following along. Use plenty of lube on the slitting saw.

 

[Longboy]

Hi all.
Just started building a twin cylinder........ with four m3 bolts ....make that three just broke a tap off in the last hole :wall:not going to get that puppy out but three will hold even two would I think......
Cheers
John

Looks like you can re- drill four new holes and tap in that same piece.....you have "experience" now!:thumbup:

 

[Johno1958]

You know, I never thought of that thanks.
John

 

[Johno1958]

Got the crankshaft nearly there. A little more machining on the rear shaft to be done . It runs quite freely a little drag due to five sealed bearings.There is two in each end one in the center. The conrods will each get two 8x12x3.5 mm thin section bearings in the big end and a couple of 3mm for the wrist pins.
It's probably going to be a long build because working night shift gives me the "Brain Fuzzies"and a lot of the time I can't be bothered.
Cheers
John

 

[Cogsy]

How did you get a sealed bearing in the centre?

 

[pp2076]

How did you get a sealed bearing in the centre?

Isn't that where the bolted bit is? ie insert bearing, bolt together...

 

[Johno1958]

Yes the first picture says it all.
I remade those two center webs after breaking the tap . Before they were a sliding fit now a light press fit . I saw this way on another forum a while back and can't for the life of me find it again but these bearings are 17mm id and 26 od and 5mm wide after using them I would have gone larger maybe 20 x 35 x 5mm
which would make thing a whole lot easier but they start to get pricey .

 

[Johno1958]

These 6804ZZ 20x32x7 Shielded Bearing would be a lot better at $ 10 or a 10 pack if you plan on using more at $47.
Cheers
John

 

[Cogsy]

Ahh, I see now. I thought it was a solid crank (confused with another build I think). I should have re-read...

 

[Johno1958]

Started on the cylinder and head.The cylinder lining is some hydraulic tube already honed .I have about 900mm of it .Bore and stroke is 25 x 34 mm.
First time I have ever used a boring head on the mill. Liked it but I have to work on getting a better finish.
John

 

[Cogsy]

Looking good, though I see what you mean about the bores being a little rough. Maybe try a few lighter cuts at very slow down feed toward the end of the boring job.

 

[Longboy]

The tool bit has to be 90 degrees to the wall of the hole you create. A lead or lag on the angle gives choppy, galling results per my first time making bores too!

 

[Johno1958]

Thanks Cogsy and Longboy.
Luckily enough I have a little bit of meat left on the hydraulic tube that can take a clean up cut.
John




Lot better

 

[Johno1958]

Just spent most of the day using a 3mm thick slitting saw and it went a lot better than I thought it would. Pretty boring doing so many cuts but it's done.
One gripe is the arbor I bought. A small arbor which takes multiple size saws and is spring loaded , I think I was only cutting on 3 or 4 teeth it was that far out.
Cheers
John

 

[Blogwitch]

John,
It most probably is not your arbor at all, but the slitting saw itself.

When they are sharpened, they don't usually redress the grinding stone half way through, so by the end of sharpening, the stone is slightly worn, and so doesn't take as much material off the cutting edge. The slitting saw ends up slightly eliptical, so some of the teeth ground at the end of the sharpening sequence will hit the job before others.

It is nothing to worry about, it is most probably less than 5 tenths difference and even helps you out with the cutting and setting up. The high spot of the saw will touch on first so take your depth of cut from that touch on and everything will be just fine.

I made my own arbors, spot on centre, and even some of my saws have the tendency to cut off centre, even saws that I have sharpened mysely using the correct setting up jig for my surface grinder.

Hope this helps

John

 

[Johno1958]

Thanks John It does help.
Saves me trying to build /buy a better arbor and it did cut well.
John

 

[Johno1958]

I have been doing a little bit more modeling to the head and cylinders. My math was out a little when I cut the fins out on top of the head as you can see one slightly fatter one.
The ports have been drilled, not all the way though yet as I want to fit the valve cages first, at 15 degrees to miss the head bolts and push rods . the manifolds are just slid in and locked with a set screw.
Now on to the base which is going to be Longboys pillar design, off I think Best Friends Four Engine .
Cheers
John

 

[Herbiev]

Looking great so far.

 

[Johno1958]

Started making the base and cam housing. It going to be quite a high engine and I have to try and put a few bevels and tapper the columns a bit
because at the moment it's one big ugly looking puppy . The cam shaft will be a made up type, on 6mm silver steel shaft running on ball bearings.

Cheers
John