Jump to content

mechanical things - 4 stroke engine


Recommended Posts

 First 1/2 of vid is running on the starter motor for demonstration.


 Lots going on here.  Lots of time spent and many craft revisions to get here.

 This 90 degree v8 has a flat-plane crankshaft, like what is used in the new Ford Mustang GT350s, Ferraris, and McLarens.  I honestly chose flat-plane because it was easier for me to program the camshaft timing, since it's more like two 4 cylinder engines stuck together (it still took forever, and it's probably still not ideal).



 The camshaft runs at 1/2 of the crankshaft speed, like in a real car.  Two things allow this to happen.



First, I created a weird mechanism to gearless-ly and efficiently drop RPMs by half (I'm very proud if you can't tell).  It took lots of youtube scouring to find a "gearless gear."  KSP gears have been good, but are inefficient.  A timing chain for the camshaft was right out - We can do wonderful robotic tank track/chains, but not at more than a few RPM.



 Second, I transferred that power up to the shared camshaft by 4 remote linkages.  The fuel lines are here just to visualize the 1:1 transfer.



 The camshaft pushes on lifters.  These lifters here have free-rolling, um, rollers on the ends for high efficiency, like in some expensive and high-performace cars.  Same Parts Interaction is enabled on staging to allow camshaft and roller to collide.



 There are no rockers.  When bumped by the camshaft lobes the lifters themselves make room for the turbines to blow on the pistons at the correct time.  The lifters are set to "spring return" at a rate of 5/100 in the hydraulic cylinder context window.



 This is all one craft.  The cylinders are attached to root, but the pistons are attached from their pins to the crankshaft journals by strut-connectors.  I didn't want to use connectors though because of their weirdness upon duplication or reverting (ctrl-z) - I never know if they'll attach correctly on other folks computers.



 Around and around we go.  So this also leaves us with two different output speeds to choose from on the transmission end - crankshaft speed (100%) and camshaft speed (50%).



  I put this in a car, but didn't get over 3.5m/s, so it's a tech demo for now.



 Good info time.

  Shift-move on the KSP snap grid is .1m on the XY plane.  A crankshaft arm of .1m radius gives us a .2m stroke.  This nice small stroke has never worked for me though.  It provides very little power but makes for a tight package (can still be used if electrically powered though).

 A .2m radius (.4m stroke) is nice.

 A .3m radius is what I chose here.  Bigger diameter = more torque.  Well, it's supposed to - doesn't matter here since there's no load.

 The smallest DLC piston total movement is .8m.  It can extend/retract further when forced, but is not meant to.  With all the stretching and flexing of high speed moving parts you don't want to be hitting the maximum top or bottom, so to me a .6m stroke is ideal to stay smooth and still leave a .1m cushion on either side of the stroke.

 This is probably TMI, and I could go on and on but I'll stop here.


Edited by klond
Link to comment
Share on other sites

  • 2 weeks later...
This thread is quite old. Please consider starting a new thread rather than reviving this one.

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...