This winter's project. A transmission for the 302 engine

[gbritnell]

The next step was to cut the first angled surface under the top of the lever. I laid out a reference line and then put it back in the mill and set the angle for cutting.

 

[gbritnell]

In this set of pictures you can see the angled surface. I have reset the part and am picking up the center of the vise and the back edge of the part with my edge finder in preparation for drilling the holes.

 

[gbritnell]

There is one remaining hole in the top of the quadrant. This will form the bottom of the slot that the shift bar engages.
I now reset the part higher in the vice so that I could cut the .078 thick area. I little explanation of my thought process for the sequence of machining. I figured if I drilled the holes before cutting this area it would help relieve any remaining stress from the CRS. and then when I made this last surface cut it would stay flat. CRS has a nasty habit of warping with successive cuts. In this case it worked out and everything stayed nice and flat. Would it have stayed flat if I did it the other way, I don't know but it's a moot point anyway.
With the .078 surface cut I reset the part to cut the second angle at the top. With this surface I would only be able to cut so far because it has to go below the pivot boss.

 

[gbritnell]

The next step was to undercut the previous angled surface below the pivot boss. To do this I will use a mini flycutter that I use for cutting gears. I sharpened up a piece of 3/16 lathe tool stock with 40 degrees on the end of it. I set the part perpendicular in the vise with my solid square and then clamped it tight. I then set the bottom of the cutter to the top of the boss and started cutting in until I matched up the existing 40 degree surface.

 

[gbritnell]

I laid out a couple of lines on the part and then took it to the bandsaw to remove the excess stock.

 

[gbritnell]

The part went back in the vise to get the little square projections cut onto it. I have no idea what they do but they were on the original part so I'm copying them onto mine.
The last 2 pictures of this set show the small square bosses on the part.

 

[gbritnell]

The next picture shows the machining of the 4 degree edge on the part. The last 2 pictures are of the part sitting on the fixture I made. I put in 2 alignment holes for the part, one at the pivot and one .25 hole that forms the radius between the 2 edges. These are square to the block so that when I machine the slots at the required angles and radii I will have a true starting point. I didn't have any tiny clamps so I milled up a couple. Tomorrow I will set up the rotary table and finish up this part.
George

 

[stevehuckss396]

Will there be any metal left when you are done?

 

[gbritnell]

Hi Steve,
Yeah, a little, :big:

This morning I pulled the vise off and set up the rotary table. Man, this thing is getting heavier or I'm getting older.
The first thing is to pick up the center of the table. To do this I start with a plug that fits nicely into the center hole. It has a small stem that I can pick up with my 60 degree brass plug. This will usually get me within .010.
Next I clamp my dial indicator to the spindle and indicate the center hole. I was .006 off in X and .003 in Y. With that done I put my fixture block on the table and using the brass center plug I lightly bring it down into my register hole which will be the rotational point for the radius I have to cut. My register hole is only .128 diameter so it's hard getting an accurate indicator reading and my plug will usually get me within .0015.
I clamp the fixture block and then retract the center plug.
The final step in the setup is to indicate one of the sides square to the machine travel.
George

 

[gbritnell]

After squaring the fixture block by rotating the table I clamp the table in place. I then set the vernier dial to -0- going up the numbers. There are 2 register marks on the table, one that is scribed into the surface and the other is a movable brass pointer. The problem with the brass pointer is it's away from the dial so you have to look two places instead of one. You can see my cure, I just make a new mark with a permanent marker.
With the table set it's time to mount the victim, I mean part. I had made two plugs from brass, one for the pivot point (.128 dia. and one that fits in the corner radius .25 dia.) I then used my new mini clamps to hold it in place.
George

 

[gbritnell]

Using a .125 dia. endmill I cut two of the slots. With everything referenced and square it's just a matter of rotating the table to the proper angles. I stayed away from the actual tangent line between the two drilled holes so that I could go back and file and fit to the proper pin diameter. Next up was the radial slot swung from the center pivot point. Here again I stayed a little shy. It's always easier to file a little off than to make a new part.
With the slots cut I put in a .062 endmill, cranked up my spindle speed (2100 rpm ???) and put the radius onto the pivot boss.
The last two pictures are the part almost complete. Apart from opening up the fork on the top of the lever and filing the slots to size I'm almost there.
You're right Steve, not much metal left from the original block but for a part like this there is no other way.
George

 

[Paulsv]

Amazing work, as always, George.

It was really great that you posted a .pdf of the drawing. When I saw that slot, I had to go back and look at it. Seeing the drawing, and then seeing how you cut it, is very instructive.

Your comment that "it's always easier to file a little off than to make a new part" applied in spades, here!

 

[gbritnell]

Today's effort was to make the link that moves the reverse gear. After completing it I just had to fit some of the pieces together to see how close my dimensions and drawings are. I cut a piece of drill rod that the reverse link and overdrive fork are operated by. I also made the pivot bolt that the quadrant rotates on. I put everything together and found that I needed to take a little out of the case to clear the quadrant.
A quick setup in the mill and and several passes with a 5/16 ball mill got everything tidied up.
All the parts were reassembled and put to the test. Everything works great. The only thing I'll do is chamfer the leading edges of the two gears so they will slip in when the teeth are in the same line.
Following are a set of pictures showing the reverse gear in the neutral position and shifted into the reverse location. It's only supposed to mesh with the countershaft the way you see it. The full sized trans does the same thing.
George

 

[gbritnell]

A couple of more close up shots from a different angle.
George

 

[gbritnell]

After much fitting, filing, assembly, disassembly, etc. I finally have the reverse/overdrive linkage working like it should. Funny, it seemed so good on paper.
Anyway here's several video clips of the whole thing.
George
[ame]http://youtu.be/OryloXGQ3gA[/ame]
[ame]http://youtu.be/yGpp20ieEl4[/ame]
[ame]http://youtu.be/IDiPWUy7BZ8[/ame]

 

[t.l.a.r. eng]

Sir, having had my hands inside hundreds of this type of trans, It is staggering the size of your thumb and fingers............ ;D

Words fall short............... :bow: :bow: :bow:

Outstanding!

 

[cfellows]

Nice, crisp action on those movements. Clearly very well made and fitted.

Chuck

 

[JorgensenSteam]

That is just awesome work George.
Fabulous.

Pat J

 

[Lakc]

Most excellent work George. Everyone loves a project you can play with like that. You may end up having to remake the top cover in lexan :big:

 

[Chitownmachine]

I like Nirvana playing in the background of one of yer videos!