Kiwi Mk2 Engine

[vcutajar]

Thanks Dave

I have no doubt that eventually I will finish the Kiwi. The only nagging doubt I keep getting is if it will actually run. I guess I will find out when I get there.

I guess every newbie in model engine building gets that feeling.

Vince

 

[steamer]

A hot spark, some compression and a dribble of fuel.....it'll run
Have faith

Dave

 

[vcutajar]

Today it was decided that the cast iron liner would be inserted into the cylinder.

I thought I would try the gentle approach first and if that did not work than the brute force approach would be used (with the press). Put the liner in a freezer bag and put it in the freezer (with permission from the wife) for four hours. I then put the cylinder in the oven (also with permission) for about 45 minutes. Took out the cylinder from the oven and the liner from the freezer and the liner just slipped in the cylinder and left it to cool off. Checked it after cooling off and the liner does not move. I did not think it would be that easy.

In photo 1 the lip of the liner is visible at the top of the cylinder and at the bottom of the cylinder the bottom of the liner is also visible. This part will go in the pocket I milled out yesterday in the cylinder platform.

Back in the garage, I used the template I had made and a homemade transfer punch (photo 2) to mark out the four holes in the base of the cylinder (photo 3).

 

[vcutajar]

Time does fly. Today I checked when I started on this project and it's been a little more than six months. I guess I am about halfway finished so I guess I should be finished by the end of this year ;D. I am not giving myself a deadline. It will finish when it's finished.

Drilled the holes I had marked yesterday in the cylinder base. I used a cone shaped wobbler to locate the marks.

Packed everything in the box as tomorrow i will be going to Germany for six days (work not holiday).

 

[steamer]

Shrink fts can be a challange. Often they go very well....other times....not so much

Well done!

Dave

 

[vcutajar]

Thanks Dave

I guess I was lucky. That's why I had plan B as a last resort.

 

[steamer]

Always have a plan B! ;D

 

[vcutajar]

It's good to be back home. Arrived yesterday but was in no mood to do anything on the Kiwi. I hate travelling as a passenger on a plane.

I also see there is lots of activity in the casting section of the forum. That's nice.

Today I continued where I left off. I need to drill and tap 4mm four holes in the cylinder platform. The plan was to use a transfer punch to mark the holes with the cylinder in place. Unfortunately due to the shape and geometry of the fins I could not use the usual transfer punch. So I made a very short version of the transfer punch (photo 1).

Marked the holes (photo 2) and drilled and tapped 4mm (photo 3). Next I will make the 4mm studs.

 

[vcutajar]

Made the studs out of 4mm threaded rod. Spent a lot of time playing around with the studs to get them at the correct lenght.

Photo 1 shows the cylinder platform with the studs and photo 2 shows the cylinder in place with one spring washer and nut to one of the studs.

Next operation will either be the drilling of the two remaining oil holes (which would complete the crankcase) or the honing of the cylinder liner.

 

[vcutajar]

Drilled the two oil holes for the two camshaft bushes.

Squared the vise on the mill table and tilted it 45 deg as per plans. Did the timing cover bush first (photo 1) and it came out well. Next I did the crankcase hole which starts from the pocket for the cylinder liner and should end up nearly at the edge of the bush (photo 2). I was already having second thoughts if the hole was going to exit where it should, but I drilled it (1.5mm). Well it ended up exactly at the edge of the bush. Not exactly where I wanted it. So I drilled another hole starting from the original one but this time used 30 deg tilt. Ended up in the bush nearly where I wanted it. So this bush will have to oil supplies.

 

[idahoan]

Vince

I have been enjoying following the progress on your Kiwi; it sure is looking good.

Thanks for the updates.

Dave

 

[vcutajar]

Thanks Dave

Welcome to the ups and downs of my first engine build.

Vince

 

[ShedBoy]

Looking good Vince
Brock

 

[vcutajar]

Thanks Brock.

 

[vcutajar]

Yesterday I started honing the cylinder liner and this morning finished it. At first I thought I would do it on the lathe but as I am a lazy person that meant changing the belts to slow it down. So I used the mill and held the cylinder in the vise under the spindle. But I was making a mess, so I removed the vise and handheld the cylinder. Photo 1 shows the setup I used. I used the bottom of a plastic water bottle and filled it with kerosene. I used a small plastic container to pour kerosene from the top of the liner during the honing operation. I was aiming for an ID of 25.4mm and got it at 25.403mm (photo 2) which is close enough. As it is the piston OD will be fitted to the cylinder.

The inside of the cylinder is smooth enough but not as smooth as if I had to polish it. I understand that it should be this way to keep oil on the liner (photo 3). Am I correct?

Now I need to ask a couple of questions (in the Question and Answer section) about piston rings.

 

[John Rudd]

The cylinder and the piston skirt should not be polished but should be smooth..helps retain the lube oil...

 

[vcutajar]

Thanks John

I suspected so.

Vince

 

[vcutajar]

After posting my question in the Question and Answer section (http://www.homemodelenginemachinist.com/index.php?topic=18754.msg194118#msg194118) I got some fine ideas to work on the piston rings.

This morning I was looking at the piston dimensions and I think I am missing a dimension on the plans. I cannot find the height of the piston. It could be I am still fuzzy this morning (came back from work in the middle of the night). The photo is a snapshot from the large scale plans I have and I think the dimension that is missing is the distance between the bottom of the second groove and the top of the hole of the wrist pin. I estimated it should read 1/16" and if so the height of the piston should be 15/16" (adding fractions is not my forte).

I think I am going back to the question and answer section and put the question there and see what people think.

 

[vcutajar]

Marcello answered the question and John confirmed it. There was a missing dimension and it should be 1/16" as I estimated. Problem is, when I added the dimensions I forgot to add the missing dimension *bang*. The height of the piston should be 1.00".

 

[vcutajar]

Well this evening I worked on the piston rings to get the end gap right.

These piston rings came with the kit and I was quiet impressed the way they were packed. They came in a plastic container padded in cotton wool (photo 1).

I held the ring in the milling vise (photo 2) and used a needle file to file the gap. As was suggested it the other thread where I asked the question about the end gap, it does not take a lot of filing. Two strokes with the file and check. Repeated until got the end gap correct. When checking the piston ring in the liner I used a piece of BMS which just fits the bore (photo 3) to push the ring in and keep it square. Used the same piece of BMS to push the ring out.

Photo 4 shows the ring in the bore but the end gap is so small that it is not visible. I was aiming for an end gap of between 0.076mm and 0.10mm. The first ring I got between 0.05mm and 0.10mm and the second ring at just below 0.05mm.

The plans call for various clearances in the piston OD, namely

Top Land - 0.006"
Ring Belt - 0.004"
Skirt - 0.003"

So if the bore is 1.00" does this mean that I machine the piston skirt 1.00" - 0.003" = 0.997"?

I am a bit ashamed going back to the question and answer section with this question so I will leave it here and see what happens.