lohmann bicycle engine
Dera psuggmog
> I am writing from India, suffer from an obsession with the Lohmann, and acquired a Lohmann in
> incomplete and worn out condition last year. I have
> been working on it for last six months and have
> restored it to good working condition. I have honed
> the cylinder 0,2 mm oversize and made a new piston
> and
> rings locally. I have also made some changes in the
> original design to improve performance. It runs best
> on kerosene/5 % 2T oil mixture. It starts easily,
> runs
> with low noise and vibration and idles at low rpm
> smoothly. It has ample power to run a bicycle with
> single rider at 30 kph at half throttle. I have
> diagrams and operating instructions. If anyone needs
> any help for restoring or building a Lohmann[a
> skilled
> model engineer can take it up as a project], or with
> spare piston and rings, or has any experience with
> running the Lohmann on bio-diesel or vegetable oil,
> please contact me.
At last after six months of hard work I am able to
enjoy the smoke and the noise of the Lohmann. It has
taken a lot of running in to get it to run without
overheating and stopping. I ran it at idle without
load using a table fan for upto an hour at a time.
Once I am able to run it for an hour, it idles at low
rpm smoothly. Starting is extremely easy, only one
attempt is usually necessary, even when starting the
first time in the morning. The throttle is very
sensitive, the slightest pressure is enough to speed
up or slow down.
I have replaced the original toggle lever for engaging
the roller with another arrangement which works much
better. I found that the original toggle arrangement
gives only two positions of the roller-engaged and
disengaged, while you need three-for starting when the
wheel is driving the roller you need high roller
pressure to prevent slipping, but this pressure needs
to be reduced for normal running when the roller is
driving the wheel, otherwise it overloads and slows
down the engine. The third position is of course the
disengaged position. I have fitted a 2 feet long
lever made of 6mm dia steel rod to the cylinder head
plate, so that it comes up to the level of the saddle.
Taking advantage of the engine being mounted on a
pin, if you move the lever forward it presses the
roller hard against the wheel- for starting. In the
middle position, it presses the roller lightly just by
its weight and the pressure is enough to run the bike
without overloading the engine, even if the wheel is
not running true. If you move the lever back, it
disengages the roller ! Not only it works well, but
you can operate it while cycling, sitting on the
bicycle seat, which is certainly an advantage.
The Lohmann is running beautifully-I can run for an
hour without stopping even once and restart easily.
I've fitted the air intake cleaner to prevent dust
going in. The sound with the spring muffler is quite
muted-a steady and pleasant purr. If the compression
is too low or throttle not opened enough for the
particular compression setting, the Lohmann four
strokes with reduced power and you have to increase
the compression or open the throttle till you get a
steady purr. There is a slight puff of smoke, maybe
because I am using too much oil for running in-10 %.
Kerosene seems to work best, better than petrol or
diesel-easy starting and plenty of power. While the
power is enough for normal running, if you have to go
up even a slight incline or slope, the engine strains.
Maybe a higher gear would be useful.
Now that its running well, I intend to use it
regularly and gain operating experience. Then I'm
wondering what to do next !
> Akhilesh Agarwal
> Mechanical Engineer