1st I.C. build "Tiny"

[90LX_Notch]

Thanks Kim. 

The reason for the order is two fold.  First, I've found that it is better to do the trickier operations early so that if something goes wrong, I have less time in the part if it is scrapped.   This was the biggest rotary table job, as far as planning and moves, that I have ever done.  I was very worried that I would make a wrong move and ruin the part.

Second, if you look at the picture,  there is a lot of air under the part.  Therefore, I wanted the part to be as rigid (thick) as possible when milling the cut out sections.  I was very afraid that things might distort with the material removal and the downward forces involved.

-Bob

[Kim]

Thanks Bob,
I can understand that reasoning, but I was thinking I'd have done it the other way so it would have been easier to do the RT milling job on only 1/3 the thickness of metal.  But this way clearly has worked well for you.
It's interesting to see the different ways people approach the same thing, isn't it?
Kim

[90LX_Notch]

Flywheels continued:

I continue to crawl along with the flywheels. 

I finished the spokes for the second flywheel on the rotary table and it was time to move onto the recess area.  A fixture was made to mount the flywheels for turning that would allow for the flywheels to removed and remounted without losing concentricity.  It is a simple fixture that does not nearly reflect the amount of time that went into thinking it up.

The fixture is made from a 1 inch diameter piece of aluminum.  A 1/2 inch shank was turned so that it could be mounted in the biggest collet for the Atlas 618 lathe.  A pip was turned to a .200 diameter by a .300 length.  The pip was center drilled and threaded for a 2-56 flathead screw.

The fixture was then moved to the mill and the pip was slit down the middle.  Also, 2-56 threaded hole was drilled and tapped on the face of the fixture .400 from center.   The fixture was then remounted in the lathe and the pip was turned to .1875, which is the diameter of the bore of the flywheel hubs.

The fixture works by tighting the 2-56 flathead screw, which expands the pip in the flywheel bore just like an expanding mandrel.  The other 2-56 screw is used to keep the flywheel from slipping on the pip.  One critical thing for a fixture like this to work is a slight undercut where the pip meets the face of the fixture.  This eliminates any chamfer or radius from the tool that prevent the flywheel from mounting correctly.

At this point both flywheels are recessed on one side.  I hope to finish machining them tonight; then the hand work begins.

-Bob


Edit- Added pip undercut.

[b.lindsey]

Those look great Bob, shouldn't be too awfully much hand work, just breaking the corners of the spokes some. Good to see more progress on your build too!!

Bill

[90LX_Notch]

Thanks Bill.  I still have to come up with a final way to mount them to the crankshaft.

-Bob

[b.lindsey]

Bob, I went with set screws,  drilled 11 degrees off vertical. Got that done tonight and seems ok.

Bill

[zeeprogrammer]

 

Very good looking flywheels Bob.

[90LX_Notch]

Thanks Carl. 

-Bob

[90LX_Notch]

Just a quick update for anyone who is interested. 

This build isn't dead or on hold.  This time of the year I don't have much free time; so projects move at a very slow rate of progress.  Recent shop time has been spent working on solving a way to accurately index for cutting the gears for Tiny.  I believe I have that solved and am currently working on making a gear hob.  Once the hob is complete, and if it works, I will post the process here.

-Bob

[b.lindsey]

Bob, I have no doubt but that your hob will do fine, but if you change your mind and want to borrow the involute cutters just let me know. I wasn't as confident as you so made the gears first (twice in fact), then played around with the ctc spacing until they seemed to mesh easily but not sloppy, and then drilled the cam gear hole in the frame based on those tests. I think in the end I deviated by .005" from the plans.

Still eagerly watching your progress.

Bill

[90LX_Notch]

Thanks for the offer for the use of the cutters Bill.  I very much appreciate it.

Not confident, more like stupid looking back at it.  I didn't think that little detail through.  Live and learn.


-Bob

[b.lindsey]

Nah, you should be fine Bob. I suspect my gear tooth depth may have been the issue even though that was corrected I thought the second time around.

Bill

[90LX_Notch]

Since shop time is so valuable at this time, I put the gears on hold and have been chipping away at the connecting rod.



Connecting Rod:

The connecting rod started off as two seperate pieces of material.  The cap and body were fitted by hand for a tight fit before being clamped in the vice.  The screw holes were then drilled and tapped.  The assembly was then setup on the mini pallet and the bores were spotted.  The pallet was then setup on the faceplate of the Rivett and bored.  (Unfortunately, I did not take any pictures of the lathe work.)

Next the split bearing was turned in the Atlas 618.  The od was gaged with the connecting rod and the id was gaged with a shop made gage.  Next the bearing stock was setup in the mill and milled to .002 over half of the required diameter.  Two bearings were then cut from the bearing stock.  The bearings were then carefully hand finished. 

To get the required angle for the connecting rod pins were placed in the bores.  A pin that is one half the difference of the two bores was placed under the pin at the piston end of the connecting rod.  It's a simple way to get a nice transition angle from the big end to the small end.  A vice stop was used so that the conncecting rod could be flipped over and both sides milled.  Then a measurement can be taken and the final cut can be made to achieve the required thickness at the small end.

The last picture shows where the connecting rod is at this point in time.   I should note that I pinned the lower bearing and provided an oil hole through cap and upper bearing.

-Bob

[b.lindsey]

Great to see you back on the Tiny build Bob. I have had a blast running it if only for my own amusement and I know you will too. Still here in the cheering section for you

Bill

[gbritnell]

HI Bob,
Like Bill said, good to see you back making chips. I'm sure it won't be too long before it all comes together.
gbritnell