Kiwi Mk2 Engine

[coopertje]

Hello Vince,

Nice work on your Kiwi Engine. :bow:

When making the tread, did you move towards or away from the headstock? If you moved towards the headstock, how did you stop the lathe to not crash your tool in the hex bar? With 3mm pitch you have quite a feeding speed...

Regards Jeroen

 

[vcutajar]

Hi Jeroen

Thanks for having a look.

I move towards the headstock and yes as you said the the feed speed is very fast. Add to that my slowest RPM is around 120 so disaster is just waiting to happen. So on the rare occasion where I need to do screw cutting on the lathe I manually turn the spindle from behind the headstock and stop exactly where I need to.

Vince

 

[vcutajar]

I am approaching the stage where I need to make the cams which is something I have never done. So I have been searching around the net on easy ways to do them. I was hoping to use the milling method and found CamCalc II (http://modelenginenews.org/design/CamTable.php) to do some calculations. Problem is I am still struggling how to use it in practical terms.

Are there any other free applications that you know of that I can have a look at with usage explanations?

Vince

 

[steamer]

Ron's is pretty good. I used it with a fixed interval of 6 degrees and it worked quite well.

A smaller interval will give a smooth cam, but 6 degrees worked very well.

Dave

 

[vcutajar]

Did not feel like doing much today. Just sat in the garage staring at the plans. Forced myself off the stool to do at least something easy. Took the cylinder liner I had previously rough machined and drilled a 22mm hole. I am already envisaging a problem with the liner when I come to bore it. The liner is 55.6mm long when finished and the maximum tailstock travel is only 58mm before it disengages from the tailstock leadscrew. Have to think about it more. In the meantime the cylinder liner is back in the box.

 

[rhankey]

I am already envisaging a problem with the liner when I come to bore it. The liner is 55.6mm long when finished and the maximum tailstock travel is only 58mm before it disengages from the tailstock leadscrew. Have to think about it more.

Are you worried how the wife may respond when you mention your current lathe is not big enough and that you need another one? I understand how that can be a problem. ;-)

Otherwise, can you bore let's say 40mm or so, then carefully slide the tail stock forward to complete the bore? If you have to clear chips, you may have to slide the tail stock in and out. I'm still relatively new at this compared to the seasoned veterans here, but when I've had to do this, advance the bit into the bore while the tail stock is locked in place, then I loosen the tail stock and carefully push it in further, while the bore helps guide the bit.

Robin

 

[vcutajar]

Hi Robin

Now that's an idea I did not think about. Get myself a larger lathe. :big: I do not think the "station manager" would approve that.

Moving the tailstock forward, I've done that before when drilling very deep holes and it turned out ok. I suspect that if I do that for boring I might introduce irregularities in the bore so I would prefer to do the whole lenght without moving the tailstock. It might still work out well with the tailstock travel that I have. I just have to give it a try. If that does not go well as a last resort I can always go visit my cousins shop and ask him to do it on one of his big lathes which he uses to earn a living.

Vince

 

[vcutajar]

Decided to redo the camshaft (the shaft that will hold the cams and the gear). I had done it exactly as per plans but it always seemed too short. So this time I made it longer so that I can trim the lenght later on. This shaft will have a 2mm groove milled in the thick portion for a 2mm key. The original shaft I had made was 6mm diameter at the widest part and 5mm at the ends which only left 1mm for the depth of the groove. The new shaft is 7mm diameter in the middle and 5mm at the ends which will give me 2mm as a depth for the groove which I think is better.

This also reminded me that I still have not received the new pinion Hemingways said they were going to send me (19th March). I think I will email Kirk and see if the gear has been sent.

 

[vcutajar]

This morning got myself a 2mm slot drill so that I can make the groove for the key in the camshaft. Was very carefull to avoid breaking it and managed to do the 2mm slot, 1mm deep for the key.

After that I started scrounging for a boring bar for the cylinder liner. Managed to find a 14mm carbide tipped boring bar which should be adequate. Had to shim up the toolpost with a couple of parallels to get the boring bar at centreline. Also had to grind a little the head of the boring bar so the it will fit. Gave it a trial cut and it worked nicely.

And that's when it dawned on me. I made a big boo boo a couple of posts ago. I was worried that the tailstock travel would not be enough for boring the cylinder liner. I am not using the boring bar in the tailstock but in the toolpost oh: *club* oh:

It must have been one of those days. No harm done.

 

[rhankey]

And that's when it dawned on me. I made a big boo boo a couple of posts ago. I was worried that the tailstock travel would not be enough for boring the cylinder liner. I am not using the boring bar in the tailstock but in the toolpost oh: *club* oh:

That was the part I overlooked in my prior response - that you were intending to use a boring bar in the tail stock, which I agree probably wouldn't be a good idea with sliding the tailstock in or out. I assumed that if you were using the tailstock, that you were using a drill bit. And if you were using a boring bar, you would be using a tool post on the carriage.

Good to hear though that you figured out a workable plan, even if it doesn't allow you to justfy buying a bigger lathe.

Robin

 

[vcutajar]

Oh well, it was one of those instances where my brain would have gone for a lunch break. Just like when trying to drill stainless (many moons ago) and the drill bits would either blunt or break and me blaming the drill bits or the material. Two days later I realised that the spindle was in reverse.

 

[vcutajar]

These last couple of days I have continued working on the cylinder liner. Bored to 25.35mm (25.4mm should be the final diameter after honing). And finished the outside diameter to dimension. Ordered from ebay a Sealey type hone kit.

Still haven't received any response from Hemingways regarding my query if they already sent the pinion gear!

 

[vcutajar]

Finished the cast iron cylinder liner. All it needs is honing but that will be done after the liner is pressed into the aluminium cylinder.

The liner was not planned to be done at this stage but as I had already started it might as well get it finished. Sprayed it with WD40 and packed it back in the box.

My original plan was to fit the timing gears and work on the cams but the waiting for a new pinion gear is creating havoc to my plans. I am surprised how long Hemingways takes to repond to emails. Maybe the next item will be to figure out how to machine the cams.

 

[vcutajar]

I think I figured out how to use the Cam Lift Calculator (http://modelenginenews.org/design/CamTable.php). This http://modelenginenews.org/feeney/pg7.html#cams helped in understanding how to machine the cam using the calculator. Decided to do a practice run to do the cams. Used aluminium rod as that is what I had at the correct size. Machined the blank for both cams and drilled it 7mm (photo 1).

Setup the dividing head on the mill and located it using a parallel test bar and DTI (photo 2).

Printed the results for the inlet and exhaust cam. Used 1 degree increments. Used a ruler to keep track of the movements in degrees and z axis using the DRO (photo 3). Finished the exhaust cam and the shape looks good (photo 4). Photo came out a bit blurry. Next time I will try to do the inlet cam.

 

[vcutajar]

Today finished the second cam and they came out good. The angle between the cams and the nose radius of the cams (which are not the same) came out spot on. The base circle diameter ended up 0.16mm undersize which hopefully I will make better on the actual cams.

I made a trial fit in the camshaft and put it in the Kiwi and it has shown me that some adjustments need to be done namely to the tappet guide. I forgot that I had left 1mm extra to the cylinder platform which means that I need to mill off 1mm from the tappet guide.

I am also having second thoughts about the camshaft being 7mm instead of 6mm.

 

[John S]

I am surprised how long Hemingways takes to repond to emails.

Doesn't Malta have bank holidays ?

 

[vcutajar]

Hi John

Sure we do and we had some many that some years back somebody decided to reduce them. Like everybody else we love the holidays.

The thing is that on the 19th March they said that they were going to send a new gear, and on the 3rd April I sent an email to see if it was actually sent. Just out of curiosity, when are the Easter holidays in the UK?

 

[vcutajar]

Decided to stop work on the cams, camshaft and timing gears until some tooling I ordered arrives and some decisions are taken. In the meantime, to do something useful, I made the crankcase oil inlet connection. There was no information on the plans of how to do it, so I made it out of 6mm BMS, tapped 5mm on one end and machined 5mm with some v grooves at the other end. It was drilled 3mm.

 

[vcutajar]

Yesterday the Sealy type hone arrived and from the looks of it is a decent honing kit. Today the other tooling I had ordered last Monday arrived and this evening started work on the cams.

A couple of days ago I made two expanding mandrels (8 and 6mm) as described by Ramon (http://www.homemodelenginemachinist.com/f31/table-engine-tale-15630/index15.html). These will be used in machining the gears to size.

 

[vcutajar]

During the last couple of days I have been slogging with the cams and today I finally finished them. They were made from a piece of 5/8" silver steel that came with the kit. I used the same method that I used in the previous trial cut of the cams. They came out fine and to dimension. I had the same problem that I had when I did the trial cut, namely from where to start the second cam to keep the correct angle between the cams. I always get confused when angles come into play. All I can say that I spent nearly an hour fussing over it to get the correct angle.

The hole in the cams was made 6mm, so I had to reduce the camshaft from 7mm to 6mm.

Also today, my youngest daughter got her driving licence and I suspect that this week will be spent mostly with her in the car than in the garage. Not really looking forward to this (is it just me?) but I guess it has to be done. Traffic here is so awful and chaotic.