An experimental V-4 wobbler

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doubleboost:
Very nice
Should be a very smooth revvy little engine
John

spuddevans:
Well, I thought I would get my finger out and get on with this build :lol: Having finished with another time-sensitive project I got back on track with this, I made a start on the two outer frames that fit either side of the main frame.

After hacksawing, squaring, and then flycutting to thickness, some 6mm ali plate down to just over 5.5mm thick, then I marked out for drilling for the crankshaft and 4 mounting posts.

After drilling the holes I then put all 3 frames together, held in alignment by as couple of 3mm drillbits, and clamped them in the vice in order to drill and tap holes M2.5 for attaching the frames to a base.

After drilling for the M2.5 holes I flycut across the bottom as they were very slight diferences between them and while they were aligned with the drillbits I thought it would be an ideal time to skim a tiny cut to level them.

Then I moved them over to my tapping stand and tapped them.

Then I moved on to shaping the outsides of the frames, 1st up was the outer frames. I have to confess, I did have full intentions of machining them manually using a base-plate jig and the rotary table, but as I had managed to get most of the bugs ironed out of my CNC system I decided to use that method instead.

That being said, it wouldn't take much to set up on a rotary table, and I still had to make a little jig plate to attach the frames to so that they can be held securely for machining, which is what I did next. Using a scrap piece of 6mm ali plate, I quickly squared it up and then drilled matching holes for the 4 3mm holes that are also in all the frames, then I tapped them M3.

Then I mounted one of the outer frames onto it and was pleasantly surprised to find that the M3 cap screws aligned quite tightly even before tightening them up, then to make sure everything was held square I ran a dti held in the chuck along one edge of the frame, and again was surprised that it was spot on ( well it was 0.05mm out over the length of the base, close enough for me )

Then I unleashed the CNC and let it do it's thing, just watched and brushed the chips away and squirted a bit of cutting fluid on from time to time until I ended up with this,

After doing the other one and a bit of cleaning up I ended up with this,

I know that the upper circular part is not centered on the crankshaft hole, I may redo that, but will probably use a couple of filing buttons and just hand file it to the right shape.

Then I set up the main frame in the jig and, because there is so much more work involved in the main frame, and some very critical distances involved with the long drilled internal steam passages, I double checked that the frame was still held perfectly square.

That's all I got done, so next will be the sphincter-tightening stage of cutting out the shape on the main frame, either you will hear from me with joy as it has gone well, or you will not hear from me for some time as I have to remake it :bang:

Tim

spuddevans:
Well, I didnt screw the frame up, but I have slightly mixed feelings as my CAM output that I made for CNC'ing the frame ended up cutting it a bit too close for my comfort. It didnt break through any of the long-drilled holes, but there isnt much left, just enough to smooth the frame.

Anyway, here's a pic of the frame after shaping and then some cleanup with files and sandpaper (yea, my inexperience with CNC is showing, but I've learnt a huge amount on this)

I then marked up the tops of the arms for the frame for drilling the inlet/exhaust pipework that will go to the speed control/reversing valve.

When I attempted to drill the holes for the inlets using a 4mm drillbit, it broke through to the top long-drilled hole in the arm (which is only 1mm or less from the top of the arm) and that pulled the drill off line and made the hole oval. :bang: So instead of having a 4mm hole that the copper feed pipe could fit snugly into (soldered to a flange that screws to the top of the arm) I had to enlarge the hole to 6mm using a 6mm endmill ( I should have used a 4mm endmill to start with to prevent it being pulled offline when it breaks into the long-drilled hole )

Then, while I had the vice stop set up I moved over 4.5mm and drilled for tapping M2, then went 9mm the other way (4.5mm the other side of the inlet) and drilled again, then I swapped over to the other arm and repeated the process. Once all hole were drilled I then tapped them M2.

Then I turned up 2 flanges out of brass, I forgot to take any in progress pics but they are very straight-forward to turn, a section 6mm diameter to fit into the holes I just made in the frame arms, and a 12mm flange with a 4mm thru hole for the copper pipe to be soldered into.

Side profile,

Then I had to make a jig up to drill the fixing holes in the flanges. Just a 6mm hole drilled thru some scrap Ali, a 2mm hole drilled 4.5mm away from the 1st hole, and a little pin I have from another jig.

Then insert a flange into the jig and drill one hole,

Then insert the pin to keep the flange from rotating, and then move over 9mm to drill the other hole.

Then I just used some files to shape the sides of the flanges, and here is one in place on the frame.

The flanges are a nice fit into the frame, which when combined with a smear of liquid gasket it should seal quite nicely.

Next up will be some form of a base.

Thanks for watching,

Tim

raynerd:
Looking great Tim and nice job on the CNC frames - your machine works great!

Chris

spuddevans:

--- Quote from: craynerd on August 31, 2011, 04:14:12 PM ---Looking great Tim and nice job on the CNC frames - your machine works great!

Chris

--- End quote ---

Thanks Chris, but while the CNC worked great, my programming in CamBam was quite lacking. There was a lot of cleaning up that I had to do. I didnt program a cleanup pass, and so I had to file out all the marks from milling it down 1mm at a time.

Another time I should program it to leave 0.3-0.5mm for a final full-depth pass to clean up.

Tim

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