A new engine for fall---

[brian Rupnow]

This is a side valve engine, very similar to the early Ford flat head engines. The head is basically just a flat steel plate with a sparkplug hole in it (and some cooling fins). There are no pushrods. All that sets between the cam and the end of the valve is a "tappet". If I want a valve lash adjustment, then it has to be designed into the tappet. I want the gears exposed so that I can easily adjust the cam timing in relation to piston position in the cycle and to each other. If the cams and gears are inside the engine, like in the engine I just finished last month, then you have to disassemble the entire engine to do that.---In fact, on the engine I just finished, the cams are fixed in relationship to each other, and the only adjustment you can make is applied to both gears with no chance for individual adjustment.

[brian Rupnow]

Now my engine can breath in and breath out----As you may have already figured out, this will be a "dry sump" engine, with sealed ball and roller bearings on the load bearing side of the crankshaft and in the connecting rod. The non load bearing side of the crankshaft is supported in "oilite" bronze bushings, as are the cam shafts, and gears. They will get a bit of oil from an oilcan when I run the engine. Tomorrow I will decide how I am going to support the engine, and what to do for a flywheel. I have thought about going to a 7" diameter flywheel with built in "fan-blades" to provide a steady draft of air over the cooling fins on the engine. I will have to model it and see if it looks reasonable or ridiculous.

[dp]

This is a side valve engine, very similar to the early Ford flat head engines.

The Harley flathead engine has the tappet/pushrods made as an assembly as everything is quite short as you can imagine. It is quite a practical arrangement. They look like this: http://www.ebay.com/itm/Harley-45-Fl...-/371111950590 . My old Plymouth in-line flathead 6 had a similar arrangement for adjusting the valves and was quite a mess when done with the engine running. T-head engines also have short pushrods. The equivalent is to put the adjusters on the valve stems. That would make for wobbly valves from cam lob sideload.

I modified my last twin-cam Harley by putting CNC-ported heads, oversize valves, and high-lift cams in it. Even though the lifters are hydraulic it was still necessary to have adjustable pushrods to fine-tune the valve train and to ensure valve/piston clearance. Too many expensive parts to trust pre-cut pushrods. I did have one pushrod come loose on the way to work, one morning, but I was able to readjust it along side the road quickly thanks to telescoping pushrod tubes. Didn't even get my slacks dirty.

[gbritnell]

Brian,
You say one of your goals is to have the cams open so that you can adjust your timing if you want. If you're going this route then you're going to have to make your gears a very fine pitch so that when you move one tooth you won't be making a radical timing change. Aftermarket automotive cams have offset holes so that the timing can be changed by a couple of degrees either way.
gbritnell

[brian Rupnow]

George--My ultimate decision was that the cams would be silver soldered to the shafts. The gear will be attached to the shaft by means of two set screws. The shafts will be free to rotate in bronze bushings. That should let me make cam adjustments with no considerations for where a particular gear tooth is located.---Brian

[brian Rupnow]

This is the point at which things begin to get a bit----goofy? The engine needs a flywheel. Past experience has proven to me beyond a doubt that the larger diameter a flywheel is, the better the engine will run and idle. Throttle response won't be as quick, because that's a lot of mass to move, but if fast throttle response isn't vitally important, then a large diameter flywheel is the way to go.
The flywheel shown is 7" diameter, which is about 1" too much in my opinion, to keep the proportions reasonable.----So----Why make the flywheel so big?--Because a second factor I have proven to myself, is that without some kind of airflow over the fins, the engine will rapidly overheat. All you guys who build these small engines with a propeller, like for instance the Nemett series by Malcolm Stride will know how much the air from the prop will cool the engines. I don't like propellers.---Having once, in my jaded past, stuck a finger into a (thankfully small) propeller on a model gas airplane, I HATE propellers. So---What to do?--I need a flywheel anyways, it has to be made from steel (can't afford brass) and I can weld steel. ----By making the flywheel 1" larger in diameter, and drilling 5 holes through the web, I can then make up 5 blades of .125" thick steel and weld them into the holes at a 45 degree angle. This will create lots of air movement, yet the flywheel will have a smooth outer rim in case some poor fool like me inadvertantly touches it. It will work. In fact, I think it will work very well. The only downside is that it makes the engine look "goofy".

[brian Rupnow]

GOOFY???

[Toolguy]

I think it looks just fine! I have an air compressor with a large pulley that has fan blades for the spokes. This has been done for a lot of years. It's the same exact thing you are doing with your engine.

[brian Rupnow]

This is a very good example of engine size comparisons. The engine on the left is patterned after the Nemett Jagauar, an engine having a 7/8" bore and a 3" diameter flywheel. The engine on the right is my new side valve engine with a 1" bore and a 7" diameter flywheel. The basic engines are very close to the same size. The new engine with the large flywheel has to have the support angle feet extended a long ways so the bottom of the flywheel will clear the table. Of course, I had to add a belt driven fan to the Nemett engine to get it to run cool enough, so it was extra work to make the fan, fan housing, blade, shaft, bushings, etcetera. I like the proportions of the Nemett engine a lot better.--Decisions--decisions---

[RichR]

Hi Brian
Well, since you are still in the design stage as opposed to having to retrofit, Maybe a smaller flywheel could work. Start with a piece of thick wall tubing and
a hub. Make up some blades to center the hub inside the tube. Add a shroud to keep fingers out and redirect all the air across the head.

[brian Rupnow]

As I have said before, I plan on using "sealed" roller (not ball) bearings on both ends of the con rod and "sealed' ball bearings on the load bearing side of the crankshaft. That is why the crank is split into two halves. Since the bearings are filled with grease and "sealed" I shouldn't have to lubricate the rod nor the crankshaft bearings. The more I look at it, the uglier it gets with that big flywheel on it.--I'm not too concerned about the airflow---the airflow hitting against the side of the crankcase will be forced out to the sides and "up and over" the cooling fins. I think I will probably go with a 4" diameter flywheel and a separate fan setting above it. That simplifies the flywheel by an order of magnitude, and I can probably utilize the computer fan/propeller that I bought for the Jaguar and then didn't use, driving it with an o-ring drive belt.--That will also direct more of the air across the cylinder and head.

[ammcoman2]

Re : flywheel



A while back I spotted a small aluminum pulley with a round groove in the periphery at a flea market. It had the cooling "fins" for spokes and it was in my grab bag in a flash - after paying for it of course.

After truing up the OD of the pulley, I shrunk a steel ring on it which is just under 3" OD, 0.75" wide and with a rim thickness of 0.375". It is destined for a small diesel engine - I think.

Perhaps this type of pulley is still available.

Geoff

[brian Rupnow]

Geoff---Run back over to the fleamarket and see if they have another, would ya please!!! Seriously, that would work fine, but not for my application. I either need a large diameter flywheel/fan that looks kind of clunky and out of proportion, or a smaller ordinary flywheel driving a lightweight fan directly above the flywheel to direct the airstream over the cylinder and head.---Brian

[brian Rupnow]

I have a few minor logistics to figure out yet, but here is the engine with a 4" diameter flywheel and the 2 15/16" diameter computer fan I bought for a previous engine and then didn't use. As far as I'm concerned, this is a really big improvement over the 7" flywheel/fan.

[dp]

That has a nice industrial strength look to it, Brian, and it doesn't look like an after-thought.