Briggs & Stratton 6S - A Beginnig

[b.lindsey]

With those done, I got both of the valve spring keepers (retainers) made. These were pretty straightforward (just small). This is shown in the 3 photos below, with the last photo showing one of them fitted to the valve spring.

 

[b.lindsey]

The only other progress was finishing up the flywheel nut just for cosmetic reasons (Photo 1) and making the small stud which will stick out of the back side of the crankcase. On the prototype, this was the attachment point for the lever start mechanism. Unfotunately I don't have the lever so unless or until I find one to model, the little 6S will just be lacking that attachment. I'm hoping the rope pull start will work just as well. Anyway, the stud is shown among the other parts already mentioned in Photo 2. Doesn't look like much for for 5-6 hours of work but its progress none the less. One more tappet and two valves to go.

 

[Deanofid]

Seems like the same thing I always say, Bill, but it's all looking good. I like how the little spring keepers turned out. Just perfect.
I see you have the degree graduated swivel top slide accessory for your Sherline. Sure looks a lot handier than turning the headstock like I used to do with my old Sherline. Nice set up.

Dean

 

[b.lindsey]

Going back to my first post today, I noted that the bushing needed a cover and a 10-32 hex cap screw. I had a small piece of stainlrss about the right size and knocked that out as shown in photo 1. The 10-32 SHCS just didn't get it so I decided to make a half scale one to duplicate the original screw shown in photo 2. In cutting the hex on the first one the end mill slipped and dug in, so a do-over was required and turned out better. The cover with the remake of the OEM type screw is shown in the last photo.

That's it fir today...I promise.

 

[b.lindsey]

Thanks again Dean. The compound accessory comes in handy at times. It has one drawback though. Depending on the angle set there are times when the thickness and width of the swivel plate can interfere with the chuck and not allow working as close to the chuck as might be desired. Its not a huge problem, but it is an inconvenience at times.

Bill

 

[b.lindsey]

This morning I took a little time just to take an inventory of where things stand. The first picture below was from back in May. The second picture is today with everything done thus far along with the now restored full size engine that the model is patterend after. It doesn't look like a lot I know but considering the carb has some 15 parts making it up, as well as learning how to make gears and springs, and with some recent progress on the crankcase and crankshaft parts... not to mention work, travels over the summer, new grandbaby and such, all in all I am ok with where things stand. It never promised to be a fast project anyway, and the drawings have been done and completed for the most part as each part was made.

Couldn't help but piece some of the sub-assemblies together as much as possible as shown in the last two photos. The more it takes shape the more inspired I get to keep the progress going now. Actually finishing up the crankcase and crankshaft is about all that stands between loose parts and assembly. Hopefully early 2011 will see the little 6S running.

Thanks to all of you that have followed along!!

 

[Deanofid]

It doesn't look like a lot I know but...

No Bill. It looks like a lot. It looks pretty much like a full sized tear down to me! Thm:

 

[swilliams]

What Dean said. That's some impressive modeling Bill :bow::bow:

 

[NickG]

Blimey - somebody has been busy! it looks amazing! :bow:

 

[b.lindsey]

Thanks to each of you for having a look. Yesterday wasn't quite as productive however. Was working on the second tappet and killed two of them before finally getting the stem diameter close enough to be happy with. I have found that even O2 drill rod once your get it down to .125" dia will deflect even with a sharp cutting bit and light cuts. That's only with a stem length of 3/4" and working as close to the chuck as possible. I am rethinking the valves now, given the discussion in another thread about 1 vs. 2 piece valves. I may try to do them in 2 pieces and use 1/8 drill rod for the stems which need to be almost 2" long. Another thought is to use 1/8" ejector pin cut-offs from my days in injection molding. These are nitrided and end up somewhere between case hardened and through hardened, but the OD is polished and consistent. Over the years I have used these extensively for shafts since their outer hardness prevents marks from set screws and such. I will ponder on that today. Either was I am now leaning to a two piece design.

Bill

 

[swilliams]

Interesting Bill

I also had some trouble with deflection when I made my exhaust valve (1/8" stem, stainless). I think it ended up with about a 1 thou fish belly after several super light cuts, and I decided that I could live with that. Another way you could attack the problem would be to rig up some sort of rough traveling steady with an 1/8 I.D. bush. I still have the inlet valve to do, I might experiment with clamping a bit of brass plate with suitable hole drilled and reamed through it onto one of the fingers on my traveling steady. That things been sitting around for way too many years without being used

How are you thinking of joining the stem to the head? Silver solder or something else?

Cheers
Steve

 

[b.lindsey]

Steve, my thought was to join the valve head and stem using silver solder. I looked last night and I do have some 1/8" Drill rod for the stems, and the head will also be drill rod. I am planning on soldering a cylindrical "blank" head to the stem, silver soldering on the underside, and then chucking the 1/8" stem in a collet to finish machining the head thickness, diameter, side angles. etc. I drew up a little soldering fixture which will allow the stem to push through the head about .250" and locate into a reamed hole. Then there will be a counterbore for the head "blank" also. This should allow the two pieces to be as close to perpendicular as possible for the soldering. The excess drill rod which will be sticking out the top of the valve will be machined away while machining the final valve head thickness. Since the soldering will be on the underside of the head, machining the top side should result in the seam between the stem and the head being virtually invisible. Since the valves in the prototype were not hardened (unlike the tappets), the valves won't have to be heat treated so there is no risk of the silver soldered joint coming loose. Given the discussion in another thread on valve head temps. the silver solder should be good to over 1000 degrees F, and with limited running, I doubt it will ever see such temps anyway. even on the exhaust side.

 

[swilliams]

Sounds like a good plan Bill. It will be interesting to see how it turns out, should be good

 

[b.lindsey]

Hopefully, I get started on this tonight Steve. I'll post pics of how it goes. Its the consistency of the drill rod that attractes me to this change of plans. I agree with you that anything within a thou or so will no doubt work and I am proceeding on that assumption with the tappets since they will require heat treating (doing that today in fact). For both the valves and tappets I am going to make some test holes...reamed to .124.125. and .126 to see which fit seems the best.

Bill

 

[b.lindsey]

This morning I fired up the heat treat furnace and let it come up to 1450 deg. F (photo 1). The two tappets were put in until they came up to temp. (see photo 2), they are so small it didn't take long) and then quenched in oil at around 150 deg F. Photo 3 shows the results, minimal scaling which flakes off easily. The end of each stem will need to be ground off slightly to get to the final length so I took a file to the ends and sure enough they are hard ! I'm cooling the furnace down now to the tempering temp. of 400 deg. F but once it gets up to 1450 degreed it takes a while to cool down that much. The stems measure between .125 and .126" on both so some further (and probably tedious) work will be needed to get them just under .125" Maybe some 600 grit paper followed by some clover compound I'm thinking to get a nice on size and semi-polished surface on the stems.

 

[gbritnell]

Hi Bill,
I have found that whenever I harden drill rod it grows a little. I can't say what the percentage is to a given cross section but when I make tools from .375 drill rod it ends up just under .376. Usually I use a fine emery paper backed by a nice flat mill file and polish it down what I need.
gbritnell

 

[b.lindsey]

Gb, Its hard to say...it didn't seem to shrink any and if anything it probebly grew .0002-.0003" There is still some very slight variation along each piece and between pieces, but the main thing is there is enough there to polish it downto fit nicely in a .125 reamed hole. Between the springs shrinking and the tappets growing, it tends to confuse a fellow :big:

It going to be a bit of a trick to hold these little parts with thin heads in order to size/polish the stems. Only thought I had was making a quick little fixture to seat the head into in the lathe chuck and then press on the stem with the tailstock center...any thoughts??

Using a good flat file as a backing for the emery paper in a good idea, and one I hadn't thought of so will give that a try

Bill

 

[swilliams]

Looks good Bill. Your idea of how to hold them sounds good to me. Another way would be to bore a small recess in the end of a bit of aluminum and stick them on with super glue. A little bit of heat or perhaps a few taps with a hammer will then get them off.

Steve

 

[b.lindsey]

Last night I gave the two piece valves a try with unacceprable results. It wasn't the theory or the design that was bad, just on these small parts I got too much heat on them too quickly. Too much heat is as bad or worse than too little heat when silver soldering. Not wanting to give up on the idea, I made two more sets of components this afternoon (photo 1). The little fixture worked well enough. Photo 2 shows the valve stem and valve head blank fitted together in the fixture with a small amount of flux applied to the area of the joint. Last night I tried applying the solder after the parts were heated (or overheated as the case was). Today I tried a different approach, making a small solder ring to fit over the stem and against the head blank as shown in the third photo. The "Little Torch" was more than adequate for this job and today I actually held the heat down (photo 4) and the combination of these changes produced a much better result.

 

[b.lindsey]

The next photo shows the results of the soldering... a nice fillet of solder all around the stem and flowing out onto the undersside of the head also. In the last photo, I had cleaned up the underside with a small radiused bit leaving a more machined fillet but leaving enough solder to keep the joint strong...or so I hope. Tomorrow I will finish maching the heads, shortening the stems to the required length, and drilling a hole for the 1/16" pin which will secure the spring keeper to the stem.

Happy Holidays!!