Another Westbury Seal 15cc

[doubletop]

It has been a quiet week with me doing other stuff but springs arrived today from AliExpress. I had intended to make my own but found these and for the price they were worth checking out. Each pack of 10 springs only about £4 delivered and tax paid



I purchased 10mm and 15mm as the length required was about12mm and maybe less when the two lock-nuts are implemented.



The two valve adjustment nuts require ¼” steel hex and I haven’t got any. But I do have lots of 4ba bolts and the heads are ¼”.



I tried making but wasn’t happy with the result. Once the head is cut off it is almost impossible to hole the result and properly finish the stub. I now have some 6mm steel hex also on its way from China £5 for a 500mm length, delivered. It was almost impossible to find any in NZ and if I had I am sure it would have cost me a lot more.

In the meantime, a trial fit with just 8ba nuts and washers. Valve #2 is the attempt with the 4ba bolt head.



I have also ordered the two helical gears from HPC Gears. They are only £10 each but wanted to charge me $55 delivery. I challenged that and pointed out that the UK Parcel Force would send them to NZ for less than £12.  They said if I wanted to do that, they would be happy to assist as long as I was willing to accept any risk and I organised the collection and delivery with Parcel Force. That was easily done on line, Parcel Force already had the HPC address in their system. I paid the fee and arranged pickup and the package was collected the next day.

Kudos to HPC for being open to alternative options.

P.S. Regarding the strength of the springs I referred to this quote from Jo on Vixens build log. The springs I have fitted are 0.4mm wire but I do have a set with 0.5mm wire, but that reduces the ID and could possibly bind on the valve guide stub of 5/32" (3.97mm) when the ID of the springs is 4mm

You want light springs that aid the dropping of the valves onto the seat, not ones that wear the cam 

Jo

and P.P.S from Jason also from the Vixen log. My 0.4mm springs are 7 active turns and the 0.5mm springs 5 active turns. So it looks like my springs should be in the right ball park

I got the old kitchen weights out

Midget 0.5mm wire 6 turns 10oz to open

Nemett wire as previous needed about 22oz

RMC with 0.45 wire, 7 turns only needed 4oz on the exhaust, inlet is less being atmospheric

Pete

[doubletop]

I have not got a lot done this week. The next job was the pistons and conrods.

I have the bronze castings for the conrods but they all have slight differences I have been struggling on where to start with them. What is the first step and how would hold them? At which point would I cut the big end cap off



I’ve been picking them up and putting them down again and referred to the sequence Malcolm Stride used for the Bobcat. That has sort of swung me towards ignoring the castings and making them in aluminium, the way Malcolm did. Then in typing this, I remembered I have some bronze bar that may do the job

Whilst procrastinating I thought I’d get on the the flywheel. I don’t have any 2.5” bar but do have some nice offcuts of 60mm stainless bar.  I launched into this without much thought as it is only a simple turning job and the top slide on the lathe is still set over to 5deg after doing the taper on the conrod. It was only when I got to the taper I realised the top-slide was set over the wrong way for this boring job. Not a problem, I’ll flip the boring bar over and do the taper running in reverse. Then I don’t have a boring bar small enough or long enough to do the reach into the recess at the rear of the flywheel. OK let’s make a D bit. That was never going to work with on stainless. Yes, I tried it.

The simple solution would be a bronze flywheel. Then the eureka moment, make bronze split collet insert, that’s what I should have considered to start with. It is how I did the Puma Flywheel using the same 60mm stainless.



In the meantime, the pistons. I still need to hone the bores of the liners and looking for a method of doing that found these, 3mm to 110mm.



So, a 16mm hone is on its way from China

In addition, I have the helical gears from HPC on their way. Ordered on 26 May and already in NZ. I could see them as early as tomorrow. Then there is the 6mm hex steel bar for the tappet nuts, also coming from China. That is also in NZ already

That’s it for now

Pete

[Admiral_dk]

Every part you have finished, looks good so far 

Per                          

[doubletop]

Every part you have finished, looks good so far 

Per                          

Per

Thank you.  Appologies for the delayed response as you will see in my next post I have been a bit occupied with the conrods

Pete

[doubletop]

I mentioned ordering a hone from China exactly a week ago. Well it arrived today. Deliveries from China these days are fantastic with regular email updates on progress. Actually from the UK as well the gears from HPC only took week. Pretty good when you remember I'm located in the middle of the Pacific Ocean



Pete

[doubletop]

Anyway Conrods

To recap. I decided that the castings were not really worth the effort of trying to get them into anything half decent coupled with the problem of were to start. I then considered the Malcolm Stride approach, in aluminium, as I had done that in the past. But I had some bronze bar so maybe in bronze and then the CNC could also add some embellishment.

A pictorial storyboard Part 1

Cutting four blanks off the bronze bar




Flycutting to size



Shaping the end caps



Cutting the end caps off



End caps fitted to their respective blanks



Picking up the crank bearing



Four blanks with conrods and gudgeon/wrist pin bearing holes





Pete

[doubletop]

Conrods Part 2

Jig for machining. Two bushes for the two bearing holes and 4mm and 6mm cap screws



Machining. Do one side then flip and do the other



First off the production line. There were a lot of chips. The as machined item was extremely light weight and had the look of those cheap plastic parts with a gold finish that you'd get on toys



All four with their bronze casting cousin. Three have been through the sand blaster the fourth just off the mill



Pete

[Admiral_dk]

The sandblasted finish looks amazing 

Per                 

[doubletop]

The sandblasted finish looks amazing 

Per                 

Yes, a magic machine that removes machining marks in seconds. The grit I am using has been in it for years, so not as aggressive as you'd imagine for these small parts

Pete

[Roger B]

Excellent progress     

As you say, CNC does move the goal posts 

[doubletop]

It looks like it has been over 3 weeks since my last post. I have been a bit distracted but have managed to get a few things done. First the pistons. Basically a simple turning job and I don’t appear to have a photo of that

The plan is to use Viton O rings as this engine is only destined for minimal running and the shelf

I fell into the trap of establishing that I needed 014 rings, going to the store and asking for 5/8” rings and getting 016 rings. I have never really understood why O rings are reference by their ID and not the OD. It is the OD that does the job.

Once the turning was complete the gudgeon/wrist pin was drilled and then the piston set up for the pocket for the little end machined.







Now time for a trial fit and the anticipated clash of the conrod with the cylinder liner was confirmed. I relieved the lower edge the liner. You can just make that out here with the witness make of the end mill just touching the lower face of the casting on cylinder #2

Also the #2 and #3 conrod caps just fouled the inner face of the casting a bit o work with a scraper resolved that problem



That didn’t fix the problem so it was back on to the conrod jig to thin the conrods.



A bit of fettling here and there and the conrods pistons and crank journals were teamed up so an initial full assembly of he moving parts could be attempted.



Without any O rings in place and powered by a battery drill all the moving parts moving in unison. That is all except #3 exhaust valve that is sticking. The valve timing has not been set. This will all come later as undoubtedly the engine will be stripped down a few more times before that is possible.

<a href="https://www.youtube.com/watch?v=8JD4Gi9MF-A" target="_blank">http://www.youtube.com/watch?v=8JD4Gi9MF-A</a>

Pete

[Sanjay F]

All the parts look great and the video of everything moving in unison is very hypnotic! 

[doubletop]

I had meant to include the difference between the design of the original conrod and the thinned version. In Westbury's original the flanks of the conrod were tangential to the crank pin and gudgeon/wrist pin diameters. I have thinned the flanks by 1/64" (0.0156) on each side. I also think the gudgeon/wrist pins are way too big say 5/32" or 4mm may be in better proportion
Original



Thinned



Pete

[doubletop]

All the parts look great and the video of everything moving in unison is very hypnotic! 

Sanjay

Thanks

It is even more hypnotic when you are the one that built it. It begins to become real

Pete

[Charles Lamont]

That all seems to be coming on very nicely. A most productive six months' work.