Briggs & Stratton 6S - A Beginnig

[Deanofid]

Nice write-up and pictures as always, Bill.
I notice there have been a few recent builds with folks using two piece valves. I'm curious about this. I've only made mine as single piece. Is there a reason for the two piece items?

 

[b.lindsey]

Dean,
In my case the valve stems were going to be about 1.700" long and I had originally designed them with some extra length on the end for a center drill and tailstock support. One of the few problems I have with the Sherline lathe is that without a tailstock extender, the tee slots on the crosslide are such that if the tool post is in the slot nearest the chuck, there isn't enough travel of the tailstock barrel to cover the width of the crossslide. With the toolpost closest to the tailstock then the left side of the crosslide will tangle with the chuck more easily. They make an extender for the tailstock but its one accessory I haven't bought yet. In this case though I had the piece of 1/8 drill rod...all nice and ground and polished and straight, which the stems need to be. As I had noted in a previous post the valves will not need to be heat treated so the silver solder will not be compromised by that...though I will heat up the bottom end of the stems and quench them to add some hardness there where they will engage the tappets. Finally the only pulling on the soldered joint should be from the valve springs which shouldn't be anywhere near enough force to strain the soldered joint. If it hadn't been for my failure on the first attempt, the whole process for making both valves should have been quicker that turning them from a solid piece, especially considering that the turned stems would have needed some extra time to polish them and work out any slight variations in diameter. Basically I think this two part process is a little more foolproof for the average guy like me, but ultimately time will tell.

Bill

 

[swilliams]

They seem to have worked out nicely Bill

 

[b.lindsey]

Thanks Steve, A few more sips of coffee and I'm headed out to the shop to try and finish them up. Pics to follow.

Bill

 

[b.lindsey]

The valves are pretty well finished now I think. After reducing the head thickness to .075" plus a thousandth or two to allow for removing the machine marks on the top of the heads, the 45 degree angle was cut. The combination of the collet adapter and the little compound angle attachment for the Sherline worked very well for this operation as shown in photo 1. Then the two dimples in the top of each valve (I assume this was used to spin the valves in the seating process in the prototype but if not maybe someone can enlighten me) were made using just the lead-in tip of a #1 center drill to a depth of .040". (Photo 2) This was done more for appearance in the model so as to match the full sixze valves. The third picture shows drilling the 1/16" holes in each stem where a 1/16" x .250 pin will slide in to hold the spring keeper onto the stem. The drilling is shown in photo 3 and the assembled valve/spring/keeper/pin is shown in the last photo.

 

[b.lindsey]

Another view of the assembled valves from the bottom side and then shown with one of the full size ones. The stems on the model valves have been left long for now until the assembly phase when they will be ground to the correct length based on the valve clearance required once the camshaftr, tappets, and valves are installed and after the valves are seated in the head.

 

[Deanofid]

Thanks for your thoughts and explanation regarding the valves, Bill. They sure came out nice, and looking just like their larger cousin.

Dean

 

[b.lindsey]

Thanks Dean, so far I am pleased with the results. Now I am pondering what to do about valve cages. The prototype engine with its cast iron crankcase just had straight reamed holes for the valves and tappets both, but I don't think that will work too well with an aluninum block. The valves might be ok but the tappets will have some side foces working on them when the cams come around, so something harder will be needed. I am thinking either a bronze liner or perhaps even a cylindrical drill bushing which would last two lifetimes, if I can find one with a small enough OD.

Merry Christmas everyone!!

Bill

 

[Deanofid]

Or maybe use cast iron for the guides, Bill. Pretty easy to machine, and worked for the prototype, too. Should last a long time.

 

[b.lindsey]

Simple, elegant, and goes back to the prototype too as you say. The machinability would be a plus too...I like it!!

Bill

 

[swilliams]

The valves came out well Bill. Nice job

 

[b.lindsey]

Thanks for having a look Steve. Before heading out to be with family yesterday afternoon, I had a few hours in the shop and got the tappets finished up and looking shiney again after the heat treating. Both of them are a nice slip fit in a .125" reamed hole now which is what I was after. Some fine emery paper backed with a flat file as gbritnell had suggested earlier worked very well though in the hardened state, material removal was very slow. Fortunately not much had to be removed...maybe .0005 or so.

 

[arnoldb]

The valves and tappets really came out well Bill Thm:

Kind regards, Arnold

 

[b.lindsey]

Thanks Arnold, sorry I haven't replied sooner. I did get a start on the center part of the crankshaft which will be cast iron. The first few steps are shown in the pictures below. I wasn't happy with the bore though...but didn't have another piece of CI at home last week so had to wait until yesterday to cut another piece at work. Will be working on that this week but the first steps will be the same. I want it to be a light shrink fit so things will stay in place for pinning. Anyway I will post further pics as progress is made.

As an aside, I had thought about ordering a piece of 1.5" OD cast iron which I could have gotten last week. Metal Express wanted $47 for a 12" piece. Checked MSC and found the same thing for $17. Couldn't believe the difference!!!

 

[b.lindsey]

Meanwhile...since I was castiron-less I did manage to draw up a few other fiddly parts, some of which had already been made and some that hadn't. One that hadn't was the little keeper that fits over the removable part of the con rod to keep the bolts from backing out. Once the bolts are installed the edges of the wider tabs are bent up to press against the flats of the bolt heads. I am not planning on relying on this alone...its more for appearance (which noone will ever see) but I trimmed, sanded,filed that out this morning from a paper template sticky glued to a piece of .009 brass shim stock. I think it came out ok but will check the fit on the con rod tonight. The third picture shows where it will fit.

 

[GailInNM]

Your progress is sure looking nice Bill.
The attention to detail, both seen and unseen is great.
I follow every post you make on this engine, but don't reply often.
Thanks for the postings.

On cast iron, Enco has 1-1/2 for about $13.50/ft. I use quite a bit of CI, so I use it to fill in orders if I need to to get to one of Enco free shipping offers. Makes it inexpensive to work with. When you look for it on their web site, it is listed as "gray iron".

Gail in NM

 

[b.lindsey]

Thanks Gail, and thanks for the info on ENCO too. I do get their flyers (seems like one every week or two). Here at the school I but a lot from MSC since they give us good pricing and are an approved vendor, etc. so I often look to them first but as you point out there are other sources out there. We do a good bit of business with Metal Express too mainly because they have a local warehouse,and usually their prices are at least aceptable, but 3X to 4X the price for a piece of CI is just unreasonable.

Thanks for following along...I know it seems VERY slow at times... but I really am gaining on it...can see the light at the end of the tunnel now...just hope it ain't a train :big:

Regards,

Bill

 

[joe d]

I know it seems VERY slow at times...

Bill: It's not a race..... :big: Been following from the start, and have been very much enjoying your project.
Keep on keeping on

Cheers, Joe

 

[b.lindsey]

Thanks for the encouragement Joe, and for following along!!

Bill

 

[tel]

I"m constantly being blown away by your attention to detail Bill - it's a wonder B&S haven't made you a serious offer.