I’ve been looking for a simpler engine to build and I came across Malcolm Stride’s Lynx, a 4-stroke air cooled engine that uses a timing belt instead of gears to turn the camshaft. So I started noodling around with a CAD model with the intention of building my own version. I am looking to design an engine that would be suitable for a second 4-stroke engine build for someone who has built a Webster and wants to take their machining to the next level.
I want to use easy to obtain parts so I selected the standard GT2 timing belt and pulleys used in everyday 3D printers. The crankshaft to camshaft spacing works out pretty well with a 320mm belt with a 24 and 48 tooth pulley. The bore will be 1" and 25mm. I live in California so I use the imperial measurement system, but wanted to try to design using Metric. I set off laying out the engine in Metric and soon found that my mind does not work in whole numbers, only in fractions with denominators of 16, and 32. So I reverted to designing in imperial. But I am determined to expand my brain and try to work in metric so I designed the engine in imperial, then designed another variant in metric. Not a metric conversion, but truly metric throughout. So I ended up with two sets of plans, one with a bore of 1" and another with a bore of 25mm. I am calling them the Lynx 90 (.90 cubic inches) and the Lynx 15 ( 15 cubic centimeters) in homage to the late Malcolm Stride. The valve train seemed the trickiest so once I figured out the Crankshaft to camshaft spacing I looked at the valve train. Something like this:
This is what I have ended up with:
I'll start by building the Crankcase Assembly.
I bore the large crankshaft hole in the block:
then square the block up on the mill zeroing the mill to this hole:
Drill and tap the holes, then machine corners off:
that is the crankcase done:
And now it is on to the front crankcase:
Next will be the cylinder sleeve and cylinder............................................
![1692550085914.png 1692550085914.png](https://cdn.imagearchive.com/homemodelenginemachinist/data/attach/103/103173-1692550085914.png)
I want to use easy to obtain parts so I selected the standard GT2 timing belt and pulleys used in everyday 3D printers. The crankshaft to camshaft spacing works out pretty well with a 320mm belt with a 24 and 48 tooth pulley. The bore will be 1" and 25mm. I live in California so I use the imperial measurement system, but wanted to try to design using Metric. I set off laying out the engine in Metric and soon found that my mind does not work in whole numbers, only in fractions with denominators of 16, and 32. So I reverted to designing in imperial. But I am determined to expand my brain and try to work in metric so I designed the engine in imperial, then designed another variant in metric. Not a metric conversion, but truly metric throughout. So I ended up with two sets of plans, one with a bore of 1" and another with a bore of 25mm. I am calling them the Lynx 90 (.90 cubic inches) and the Lynx 15 ( 15 cubic centimeters) in homage to the late Malcolm Stride. The valve train seemed the trickiest so once I figured out the Crankshaft to camshaft spacing I looked at the valve train. Something like this:
![1692550615522.png 1692550615522.png](https://cdn.imagearchive.com/homemodelenginemachinist/data/attach/103/103174-1692550615522.png)
This is what I have ended up with:
![1692552706043.png 1692552706043.png](https://cdn.imagearchive.com/homemodelenginemachinist/data/attach/103/103183-1692552706043.png)
I'll start by building the Crankcase Assembly.
![1692551408483.png 1692551408483.png](https://cdn.imagearchive.com/homemodelenginemachinist/data/attach/103/103176-1692551408483.png)
![1692550954676.png 1692550954676.png](https://cdn.imagearchive.com/homemodelenginemachinist/data/attach/103/103175-1692550954676.png)
I bore the large crankshaft hole in the block:
![1692551636956.png 1692551636956.png](https://cdn.imagearchive.com/homemodelenginemachinist/data/attach/103/103178-1692551636956.png)
then square the block up on the mill zeroing the mill to this hole:
![1692551755523.png 1692551755523.png](https://cdn.imagearchive.com/homemodelenginemachinist/data/attach/103/103179-1692551755523.png)
Drill and tap the holes, then machine corners off:
![1692551862646.png 1692551862646.png](https://cdn.imagearchive.com/homemodelenginemachinist/data/attach/103/103180-1692551862646.png)
that is the crankcase done:
![1692551962694.png 1692551962694.png](https://cdn.imagearchive.com/homemodelenginemachinist/data/attach/103/103181-1692551962694.png)
And now it is on to the front crankcase:
![1692552077372.png 1692552077372.png](https://cdn.imagearchive.com/homemodelenginemachinist/data/attach/103/103182-1692552077372.png)
Next will be the cylinder sleeve and cylinder............................................