5 Cylinder Radial

[Brian]

Cam shaft blank made ready for cutting the cams, bearings have arrived just need the time.
 Brian.

   

[Brian]

Cutting the cams.

   
 

Ready for finishing to size for the bearings.


   
 

Waiting for the screws.

      

When the screws arrive I will be able to cut the valves to length and set the valve lash.
Brian.

[pepi]

Brian,

Do the intake and exhaust have the same lift and duration?

[Brian]

Hi Pepi
Yes the valve timing is equal as per the diagram below
   

The valve lift is 2mm this comes about by measuring the available throat area  ( area of throat minus area of valve stem )and ensuring that  the lift area (diameter of throat & lift) is similar. as my valves are the same size this value
is the same.

Brian.

[Pete O]

G'day Brian, this might be difficult to answer but can you explain how you convert the valve timing diagram to an actual machining operation to produce the cam profile and the desired relationship between the inlet and exhaust lobes? I was hoping to see a video!

[Brian]

Hi Pete
Are you ready have you got the popcorn and a comfy seat.
 First I must explain this is for flat sided cam. the lift on my cam is only 2mm so I see no benefit in trying to make a curve in it.
A valve diagram normally shows the overlap in this case 20° and the lead and lag both 45°, but we need to know the time the valve is open here it's 235°.
   


Now remember this is crank angle so we must halve these figures for the Cam running at 2-1 ratio.
So we will start with the base circle of the cam then draw a vertical line through it this is the position of the cam at TDC, now we know the overlap is 10° for each cam, so half of that is 5°and we put a line in 5° before TDC.

The valve opening period is 235°, half of that is 117.5° OK I am going to forget about the .5 and draw in a line
117° from valve opening. and draw another line half way between the two to show full open position.

Now look at the point where the Opening line meets the base circle and draw a line at 90° this is one flank of the cam,
repeat at the other side, then we only need to put in another circle to give the lift and rub out the bit we don't want.
 

Repeat for the other side, then measure between the two cam peaks and we get 107°relationship between the cams.
     
,A quick break for a beer and to do another drawing , Then on to the machining.

Any questions??   Brian.

[pepi]

Both post are interesting Brian.

Thanks will read them again to absorb more...

[Brian]

Ok off we go again.

We now have all the details we need .

     

From this we can now find the amount we have to remove to cut the cam, the valve must be open for 117°so 360 minus 117=243° To cut away.

OK into the work shop  and make the blank, then on to the mill.

I try to keep things simple when machining. I have a job to remember what I have taken off  without plus or minus extra's. so when I use the rotary table I prefer to always work from zero.

My RT has a extra fiducial mark 90° from the original one to help when the table is used vertically this mark is also adjustable . in the past I have used temporary stick on marks for this type of job.

     

 Right we know the relationship between the two cams is 107° so set the RT to 107° then set the adjustable
mark to 0° 
Set up the blank on the RT  with a tail stock centre or a machinists jack to keep it firm,  set the RT to the new zero,

Use a end mill with a diameter about one and a half times the width of the cam and bring it down to just touch the blank of the exhaust cam with front one third of the cutter.    add a little feed to the Z and rotate the RT to 243° Then return to zero,

Back away the Y feed  add  more Z  then bring the cutter back to position. turn the RT when you reach 243° you will need to move the cutter forward to flatten the flank of the cam. Repeat this untill you get to your desired lift.    Mic the base circle as a double check .

 Now back off the cutter , move it over the inlet cam blank,  Move the RT so zero is at the original mark and repeat the operation from the original mark.

When finished a nose radius is put on with a stone .  Remember your cam may go the opposite way depending on if it is belt or gear drive. just reverse the order and start on the other mark.

   

I hope this answers your question Pete.
Brian.

[TomG]

Hi Brian,

What steel did you use for the cams. Will they be hardened and polished?

Tom

[Pete O]

(02-26-2016, 10:30 AM)Brian Wrote: I hope this answers your question Pete.
Brian.

It sure does Brian, whether I can take in the answer is another matter! It's just after 3am here and I'm 3/4 of the way through a 14-hour nightshift so methinks I'd better read this again in a couple of days to have any hope of getting it. I was imagining the machining to involve offsetting the workpiece in the RT. Thanks for taking the time to explain, very interesting stuff.