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Your Own Design / Re: Building a twin cylinder inline i.c. engine
« Last post by Mike R on Today at 08:59:45 PM »
Laurentic--Yes the compression ratio was changed. Was it changed enough to keep the engine from running? I doubt it very much. I didn't do an actual calculation on it.---Brian



Brian,


What was the thickness of the spacer under the cylinders? To me it looks like its about 1/8" (3.175mm)?  That is going to have a significant impact on the compression ratio of the engine. 


The following are assumptions as we don't have all the details, but I think it gives a good idea as to what may still be wrong with the internal combustion process (induction, compression, ignition, expansion and exhaust). 
Assuming that you designed it initially with the a 6:1 compression ratio (as a copy of Malcom Strides Bobcat), using your modified 25.4mm x 22mm bore and stroke we can reverse engineer a few things:
total displacement = 11.15cc with compression ratio 6:1 results in a design intent of 1.86cc combustion chamber volume


adding the volume the spacer adds (assuming 3.175mm) = 1.61cc  plus the original chamber volume of 1.86cc = 3.47cc combustion chamber volume as built.
working that out 11.15 to 3.47 is roughly a 3.2:1 compression ratio - likely too low IMHO.


Brian, you have been asked a few times about how the engine behaves with a bump test - its not a pointless exercise - it will help validate if there is compression, and how much is there.  We don't need a psi # to know if there is no compression, just spin the engine by hand - is there resistance to compression once per rev and if so does it feel good (snap over TDC) or is it "soft"? Take a video as you do it, and share,  if you really want some help from those on this forum. 




Suggestions for anyone else looking for help on why their engine will not run:


1.  provide all possible info:
   Is it built to an existing design or is it a new or modified design?
      If modified - what did you change?  details matter when things aren't working.
                    In this case Brian has changed a fair amount I understand:
   Cam tower height,
   valve length
   valve spring
   Cylinders spaced up (i.e. reduced compression ratio)
   induction (twin carb)
   bore and stroke,
        o-ring piston ring
   crankcase size,
   etc. , etc. to the point that I think it is effectively a new design (along with all the possible errors that come with a new design).


2.  Can you provide a video?  If so it should show if possible:
   a.  slowly turning the engine over - is there compression resistance as its turned over? For multi cylinder is there resistance as each cylinder comes to its compression stroke?  Does the engine "snap" over TDC, or is it "soft" when turning over.
   b.  If spark ignition, does it spark when turned over (assuming coil ignition or CDI, not magneto) and spark approximately when it should (just before TDC on compression stroke)?
   c.  slowly turning the engine over, show direction of rotation, and if possible the valve actuation (for each cylinder if multi cylinder)




Regards,


Mike

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Chatterbox / Re: Is Facebook as bad as I have read, or is it OK?
« Last post by gipetto on Today at 08:08:49 PM »
a friend of mine finds non running atv and motorbikes on facebook marketplace all the time, repairs and resells them. he makes quite a lot of money at it. in ireland there's more of that stuff on facebook at a low price than on any classified website. He often shows me pics of stuff for sale on it.
as for the site though,  i had an account and made an ass of myself talking to people that i remembered from years back. do not recommend, and I have since deleted it. internet friends are not real friends, you can't make a connection over it and since your every communication is monitored and monetized, it will actively impair your social skills by warping what you want out of friendship.
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Your Own Design / Re: Building a twin cylinder inline i.c. engine
« Last post by Brian Rupnow on Today at 08:01:27 PM »
Jason---the ones I made are setting in a jar and will be used in a future engine.---Brian
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Your Own Design / Re: Kearsarge Windlass Engines
« Last post by crueby on Today at 07:39:49 PM »
More done on the engine bed, got the side cuts on the first side done. The top ends of the vertical flanges will be cut back, so they are full width at the bottom and taper in to meet the side of the base at the top.


Then got to work on the other side. This is a bit more complex because of the extensions sticking out from the crank web openings. The solid block just left of center in this picture needs to be undercut - that block is there to form the angled holder for a frame post.

So, here is the engine bed so far, mounted back on the base without the plywood spacer. Next steps will be to lay out and cut the bearing block openings, and drill all the holes in the top faces for the frames and bearing caps. Lots to go on this part!
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Your Own Design / Re: Kearsarge Windlass Engines
« Last post by cnr6400 on Today at 07:24:10 PM »
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:
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Your Own Design / Re: Kearsarge Windlass Engines
« Last post by crueby on Today at 06:49:21 PM »
Just out of idle curiosity, did you Count the Number of Cranks it took to bring the top down to finished height?  That was some mighty fine CNCing.
The bar was 1" thick to start, finished height was 0.9", so two cranks vertically. Horizontally? Thats a LOT!  Back and forth and back and forth...
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From Plans / Re: 30ft 1890's navy steam launch 1/6th scale
« Last post by tghs on Today at 06:21:08 PM »
learning the joys of turning copper!!! :wallbang: but got the parts done.. upper section of header pipe soldered up.. had to temporally mount the vacuum gauge I purchased a while back (also have its match in a pressure gauge) no complaints out of Slim (for now) :cheers:
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Your Own Design / Re: Building a twin cylinder inline i.c. engine
« Last post by Jasonb on Today at 06:15:19 PM »
What happened to the ones you already made with rounded flanks that you decided to swap out for the flat flank ones?

Can't you just put those back in
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Chatterbox / Re: Is Facebook as bad as I have read, or is it OK?
« Last post by ddmckee54 on Today at 06:02:47 PM »
A couple of years ago I found a vintage Cub Cadet garden tractor that wasn't too far from me on FB Marketplace.  Up until that time I had avoided FB like the plague.  I joined FB, just to be able to communicate with the seller.  I set up a tentative time to look at the tractor.  A couple of days later I tried to communicate with the seller again to verify the time, and found myself banned from FB for "Improper use of FB Marketplace."  I've never gone back since.

Don
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Your Own Design / Re: Building a twin cylinder inline i.c. engine
« Last post by Brian Rupnow on Today at 05:54:59 PM »
A big Thank You going out to Nelson from Kansas. Nelson has a tabletop cnc machine and used it to make four cams for me which DO have the flank radius machined into them. I will drill and tap the set screw holes and harden the cams myself. For all the people out there who said that a tabletop cnc machine is not capable of machining metal, these certainly look good to me. If I don't use them on this current engine, they will be used in a future engine.---Brian
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