From what I can gather the baby four stroke Honda seems to be the quietest thing around in this engine size, but it would be very easy to make the unit very quiet by adding an additional absorption type silencer and enclosing the whole "hybrid power pack" in a well insulated (and ventilated) enclosure, similar to a low noise generator.
The DARPA sponsored military micro generator does exactly this, and it uses a very much noisier core engine - a diesel model aircraft unit.
I haven't yet had a chance to hear one of these small four strokes; they seem to be pretty rare here as far as I can see. I may well do a quick tour of the local garden centres and see if I can persuade them to let me hear one running. I doubt it can be any noisier than the small two stroke strimmer I have, and that is really pretty quiet - the whirling string makes more noise than the engine when you rev it up.
My new Crystalite front wheel and controller arrived today, so I think the rest of this weekend will be taken up with me converting my recumbent. I've deliberately left the rear rack clear of batteries, controller, etc, so that I have space to fit a hybrid power unit once I get the details sorted. Meanwhile I will be working on fine tuning the rest of the bike!
Jeremy
The DARPA sponsored military micro generator does exactly this, and it uses a very much noisier core engine - a diesel model aircraft unit.
I haven't yet had a chance to hear one of these small four strokes; they seem to be pretty rare here as far as I can see. I may well do a quick tour of the local garden centres and see if I can persuade them to let me hear one running. I doubt it can be any noisier than the small two stroke strimmer I have, and that is really pretty quiet - the whirling string makes more noise than the engine when you rev it up.
My new Crystalite front wheel and controller arrived today, so I think the rest of this weekend will be taken up with me converting my recumbent. I've deliberately left the rear rack clear of batteries, controller, etc, so that I have space to fit a hybrid power unit once I get the details sorted. Meanwhile I will be working on fine tuning the rest of the bike!
Jeremy