Briggs & Stratton 6S - A Beginnig

[b.lindsey]

After a small misstep last night, I got a start on the cylinder head after work today. The blank was roughed out and the basic hole pattern drilled. Hopefully tomorrow I can get the spotfacing done at each hole location.At this point just trying to get something done each day.

 

[NickG]

Looks perfect!

 

[b.lindsey]

Just a smidge of progress today...milling down to the various heights of where the head bolts will meet the head to hold it to the cylinder block. Nothing special there...the fins will come next.

Bill

 

[Deanofid]

Yes, I can see a head in there, just waiting to come out.
I'm sure you're the guy to find it, Bill!

Dean

 

[b.lindsey]

Nick...not sure about perfect but thanks....you should have seen the one i screwed up the previous evening...fortunately I was just starting on it...but hey, its making a nice paperweight.

Dean...thanks for the vote of confidence...I'll try to coax it out somehow

Bill

 

[b.lindsey]

A little backtracking today. The starter hub was one of the earlier parts finished and needed the wire mesh screen formed to fit around it. I had some fine mesh stainless screen but finally got around to making a forming tool...nothing elaborate, just a piece of nylon machined to the correct sizes. The pics below were taken after the fact but the procedure was the same. A template was cut out and glued to the s.s. wire mesh. Cutting the OD was no problem but the .688" ID proved too small for scissors or snips. I finally got a small hole through it and then used the dremel to grind out the ID to the template lines. Four little snips allowed the resulting inner sections to be bent (sort of) with an aluminum plunger as shown in photo 3. Some additional hand bending was required to get the bend to near 90 degrees. The dashed lines on the template are the bend lines byt the way.

 

[b.lindsey]

After the inner tabs were formed the outer rim had to be formed. The other side of the forming tool was used for this and the inner tabs helped a lot to hold it in position. The outer rim was all formed by hand bending and some tapping around the entire edge with a small ball pein hammer. Even then, a little more hand forming was required after removal. To my surprise the wire held together well and didn't even offer to unweave itself. As shown in the last photo the inner and outer diameters seem to be acceptably concentric. For size reference the OD of the finished screen is 2 inches.
It should be a snug fit to the starter hub and I am still deciding how to attach it permanently to the hub, though that won't be done until later as things begin to go together.

I'll try to take a pic tonight of it fitted to the hub.

EDIT: one of the photos had to be reduced in size...so the reference to the last picture refers to the middle picture below.

 

[b.lindsey]

OK...I jusy couldn't help fitting these few parts together as they will eventually fit. Another little loose end tied and I am happy with the results. Here are a few pics of the starter hub (with its dress on) and her big sister. The mesh on the model is a bit finer that the original (even scaled by half) but it was available. Guess I will just have to find some quarter scale debris to keep out of the flywheel

 

[rake60]

Amazing work Bill! :bow:

I sit here thinking, how could he possibly model the next part.
Then you show it! I am totally watching for more!

Rick

 

[slick95]

Very nice Bill

Looking forward to the next part also...

Jeff

 

[zeeprogrammer]

Wow.
I guess I hadn't been keeping up. I was enjoying the last few posts and ended up going back to the start of the thread. It's a great thread...some very nice work here.
Very enjoyable Bill...very nice stuff.

 

[b.lindsey]

Thanks Rick and Jeff.The more I get done, the more I can see it in my head ...there's still a long way to go though, a lot more parts to make, and challenges ahead, but its been a fun journey so far and the most ambitious project I have attempted. Thanks to all for the interest and to you Rick for your shared knowledge and Briggs expertise!!

A quick question to other IC modelers. As I look ahead to the con rod which is already drawn, would aluminum be sufficient from a material standpoint or should I consider something stronger like bronze. If aluminum is acceptable, should it have bronze sleeves for the wrist pin and crank or would just the aluminum suffice?

Bill

 

[b.lindsey]

Thanks Zee...I have been following your 0-4-0 thread with great interest also.

Bill

 

[Deanofid]

This looks great, Bill. Every step you make is very well done.

The con-rod;
I don't know the bore and stroke on your engine, nor it's expected rpm. One I made uses an aluminum rod and a plain bearing on the rod big end. It has a bore of 3/4" and a stroke of 1" and splash lube. I think it only turns at around 1000 rpm, though. It has quite a few hours on it for a small engine. Probably 15-20. I took the crankcase cover off a few months back just to have a look at things, and couldn't detect any wear in the bottom rod bearing.

George Britnell can probably tell you all you need to know about what to use, material wise. Maybe PM him, if he doesn't chime in here.

Dean

 

[GailInNM]

Looking good, Bill.

At the wrist pin, below most of the commercial model airplane engines below about 0.4 CID just used hard aluminum, like 2024, for conrod with no insert. Above that bronze bearings started to show up.

With the limited amount of running that a display/show model gets, I think a 2024 conrod would be fine. You probably wont be trying to get the ultimate amount of power out of it either like working engines. I think that I did sleeve one wrist pin bearing on a 1 inch bore engine, but that is probably because I had a suitable bearing on hand. I have never built any high performance larger engines. The wrist pin needs to be well polished and case hardening is an advantage. Dowel pin works well if a suitable one is available.

Gail in NM

 

[b.lindsey]

Thanks for the advice guys. As info. both the bore and stroke are 1.00". As I figure it that puts the displacement somewhere around .785 cu. in. I see this as being used only for display purposes and even then at idle rpm's more ofthe than not, though I would expect it to run at over 1000 rpm at times. The original engine manual showed HP ratings at 2200, 2700, and 3200 rpm but again I don't expect to run it at anything near those speeds as a rule.

It will have splash lubrication just as the original did as there is a small "finger" attached to the bottom end of the con rod which dips into the oil in the base and "flings" it within the crankcase on each revolution.

I am planning on using a dowel pin for the wrist pin Gail for the reasons you mention and fortunately that scales down to a 1/4" so that shouldn't be a problem. Since the piston is aluminum also, I do want to make sure the wrist pin is well fixed in the piston and not free to turn since I can see that wearing out the wrist pin bore rather rapidly. The original con rod was cast and then machined with oil grooves at least on the crank shaft end but I can't tell if it was cast from aluminum or possibly magnesium.

If George doesn't chim in here I will give him a shout too.

Thanks again.

Bill

 

[b.lindsey]

Today was the annual Swap Meet for our local antique engine club and I was on a quest to see if I could find some of the missing parts for the full size 6S I am modleing from. I didn't find parts per se, but I did find two more 6S's...with most if not all of the missing parts I need intact. Both had good carbs, decent air filters, and non-leaking gas tanks.

The pictures below show the front and back side of each. The one in the first two pictures is missing its nameplate and muffler but I did see it run briefly so it is in near running condition and the bearings feel fine too....no slop in them. Of the two, this one is grimier but in this case I think that is good because its "innards" probably haven't dried out as much, At least the exhaust valve as view through the missing muffler port still seems oily.

The second one (pictures 3 & 4) isn't in as good a shape and the bearings have some significant wear, but the air filter was more of the type I am modeling and it has the better gas tank too. It also had a nameplate and going from the serial number it was manufactured around May-June of 1952 or about 18 months later than the 6S I am modeling.

Hopefully between the three I can come up with one working engine that can be restored and be displayed side by side with the half scale model.

 

[b.lindsey]

When I got the new additions home and compared them to the crankcase I already had I noticed that the second one pictured above, the one with the nameplate had the oil drain plug on the opposite end of the base. I am wondering and hoping that Rick or other Briggs fans can shed some light on this. Otherwise all the castings appear to be identical. The other question I have is that the engine without the nameplate (pics 1 & 2 above) has an extra little cover extending from the top of the flywheel cover up over part of the cylinder head fins. Since I can't date this one (missing nameplate) I was wondering when this change was made? Any help would be muchly appreciated.

Bill

 

[rake60]

That is interesting Bill.
I have never seen a 6S with the oil drain on the point end of the base.
It may have been a special arrangement to better suit a customers application.
You can still date it with the stamping in the back face of the flywheel.

Nice score! Thm:

Rick

 

[b.lindsey]

Yes Rick, I recall the flywheel method thanks to you, just didn't break them down that far yet, but i will to check that and the points as well. I did discover an extra little diverter blade inside the flywheel cover which seems to divert more air to the cylinder head when the throttle is more open...at least that wahat it looks like to me. Another part to model scratch.gif

Bill