Hamm, some of my conclusions.

[oldbmw]

This is a long post, and in fact I have been debating whether or not to write it. It may seem negative but please do not take that view. I see current diesel bikes as being something like the scene with British bikes in the late fifties. They are about to make some significant improvements. Despite what many will tell you about stagnant development, most British bikes went to unit construction and AC electrics during that time.

I went to the 2007 Hamm rally this year, my first visit. I met up with Stuart and Jeff after they had disembarked from the ferry at Dieppe. From there we made our way to Mons. I had not seen a diesel bike in the flesh before and was surprised how agile Stuarts bike was up to 45 mph. It also cruised happily at 50 to 60mph when up to speed. The only time the diesel was at a real disadvantage was when on the German autobahn, mainly because there lorries are not allowed to over take and from time to time we were slower than them.

At the show I spent my time looking at the various models, some such as the Somer production bikes, and others home brewed. They can be broken into two camps, those using Enfield as a base bike and those not.
The Enfield we have now is essentially the 1955 model 350 or 500 base machine. The engine fits snugly into this frame. It is of significance that the Redditch factory strengthened the frame in the early 1960’s when they fitted the more powerful parallel twin engines.

The Indian made diesel variant had a motor that was virtually the same dimension as the original single cylinder motor, consequently it was a good fit to the frame. Most of the other conversions I saw cut away significant parts of the front down tube in order to accommodate a bigger engine. I believe this weakens the frame, especially around the area of the steering head. Given that the frame is already near its limits I think this is a bad idea. Many had an alternative assembly, most with the join being held together with two bolts which looked to me as more likely to pivot than provide support for the steering head. What I think would be better would be to cut the backbone tubes and weld in a small extension and at the same time beef up the backbone and steering head. This would give all the space needed, and improve rather than weaken the frame. This would be especially useful to those using the Hatz IB40, as then you could make room for the five speed box.

Almost all the engines used were industrial engines designed to run at a fixed 3000 or 3600 rpm, in order to run generating sets. These speeds coincide with European 50 Hz electrical supplies (3000) and American 60HZ at 3600rpm. Because of this the fuel injection system is statically timed for peak efficiency at those rpms. Unfortunately this is too far advanced for quiet idling and any low rev power. This makes the power band very narrow. Sadly the Enfield four speed gearbox has a wide change of ratios between third and top, which means the engine drops to the bottom or below the power band when changing from third to top, The five speed box avoids this. This is why I advocate using it.

The other problem which needs to be fixed is the timing. Somehow we will have to get variable timing if only a two position, slow speed and fast speed setting. Having looked at a few pumps, I have not yet thought of a solution to this problem. I had hoped they were like tractor and older car pumps, mounted radially so could be manually controlled by a handlebar mounted control lever like the old fashioned manual advance and retard of fifties bikes.

I think for myself, I would want a bike with these attributes plus enough power to cruise at 70-75. I did not see the bike for me at the show, but many showed promise.

[balboa_71]

Oldbmw,
I'm glad you took the time to write...good information. I won't comment on the Enfield frame as it's been a while since I owned one of these bikes and don't remember the specifics. As for the timing issue a few things come to mind: the high pressure steel line between the pump (clone engine) and injector cannot be moved around, so rotating the pump (if this were a possiblility solution based on design) is out of the question. To alter the timing, one has to alter the cam orientation of the cam lobe and that would have to be done with weights and springs.....engineering nightmare. The other thing is compression ratio and it's effect on timing....lowering the compression to alter the combustion timing and finally a two stage pump with pre-injection which I don't really understand it's effects. Since I run a clone engine, I'm painfully aware of the noise caused by early injection.

Thanks for the write up,
Cris

[Diesel Dave]

A good synopsis I think.

I came to the world of Diesel bikes from the Enfield camp and I still run a petrol 500 so I could be described as a bit biased but I like the riding position and great handling these little bikes have.

A couple of points.

IB40's can't take the 5 speeder because it clashes with the fan shroud and flywheel, to space them further apart so as to make room would entail making up a new primary case or moving to a belt drive with a longer belt and fashoning up a new primary cover.

Variable timing on stationary diesels - hmm the only way I think this can be done is to engineer variable cam timing, move to electronic control (common rail); or to use a car injection pump on a toothed belt drive.

Using a CVT is a good way to make the most of a single speed motor though.

Chopping the downtube is always going to be perceived as a bodge but it's a lot less risky than extending the frame from the top tube.

The bike that really took my fancy at the rally was the Punsun Enfield, it fitted the 5 speed box, and had an additional outrigger bearing for the extended gearbox shaft. So this will be the bike for me to build over the winter - the only difference mine will have will be the disk brake front end 'cos this is what I have already.

I believe we are still the vanguard of things to come, we are the pioneers in the same way that early motorcycles were. Some of our bikes are slow and vibrate but you cancertainly say the diesel bikers cover the miles.

One chap was proud to announce that at 42,000kms it was time for his first tappet check. Others rode 9 hours from Bavaria to get to the event and Olaf rode the whole way from Finland at 30mph on his semi-recumbent rat bike.

I think I'll be a diesel bike for many years yet and when the general populous are riding around on biodiesel scooters in 20 years time I can say proudly - I was there at the start.

Twas great to meet you.

Regards
Dave

[sbrumby]

I think you are missing the point of diesel bikes altogether. For me & I dont speak for anyone else, diesel bikes mean economy & reliability. I have an interesting graph called the physics of speed. On the left is bhp & on the bottom is mph. the curve is rather flat at the bottom then it curves uphill. There are a lot of dots on the graph which are various bikes, some appear above the line example Harley, Goldwing,Bmw etc. What this means is they have the hp but not the speed basically they are heavy. The bikes below the line Ducati, Fzr1000,Yamaha R1, etc are light sports bikes with big hp.The one on the top is Ducati Desmosedici 250bhp 215mph. The interesting thing is, it says if you need 250mph you need 500bhp. So if you need to cruise at 75mph I would sidestep the Enfield variants check the state of the pigibank and put a deposit down on the Neander. Just think a little into the future, oil has now hit 80$ a barrel will your view be the same when it hits 200$ not so far away in my view.

[oldbmw]

I think you are missing the point of diesel bikes altogether. For me & I dont speak for anyone else, diesel bikes mean economy & reliability. I have an interesting graph called the physics of speed. On the left is bhp & on the bottom is mph. the curve is rather flat at the bottom then it curves uphill. There are a lot of dots on the graph which are various bikes, some appear above the line example Harley, Goldwing,Bmw etc. What this means is they have the hp but not the speed basically they are heavy. The bikes below the line Ducati, Fzr1000,Yamaha R1, etc are light sports bikes with big hp.The one on the top is Ducati Desmosedici 250bhp 215mph. The interesting thing is, it says if you need 250mph you need 500bhp. So if you need to cruise at 75mph I would sidestep the Enfield variants check the state of the pigibank and put a deposit down on the Neander. Just think a little into the future, oil has now hit 80$ a barrel will your view be the same when it hits 200$ not so far away in my view.

I am with you on oil prices, in fact energy prices in general. It is this reason I have planted out about four acres of coppice. It will provide more than double any heating/cooking requirements for the farm here for several hundred years. The reason I palnted 2-3 times as much, is when i get too old to swing a chainsaw, someone will do it for me and be paid with some of the wood I dont need. I think the most efficient solar heating in teh world is a hectare or so of coppiced trees:) Also a diesel engine would likely run on sunflower or rape seed oil, both of which i could produce here.

But when you say economy the numbers do not stack up. Taking your example of teh Neander against my BMW means I would have to ride the Neander 950,000 miles before I got to break even point. At 10,000 miles a year that would take 95 years. Sadly I dont think I will have the time
Perhaps a better example would be a new Enfield Electra against a Somer diesel. With a couple of extras, better seat and bigger tank the electra would come in at £4000, and the Somer at about £5000. Assuming the electra does 80mpg and the Somer 160 mpg it would take 32,000 miles to break even ( Approximately) Three to five years for me. This is fair enough, except I think the Electra would be nicer to ride ( very subjective I know) This is because the electra could match all the slow speed attributes of a Somer, but.. also manage faster bits of motorway much better. IE it could hold 75mph maybe not where the electra is happiest, but certainly doable, not so for teh Somer.

One thing I forgot to say in my original post, I think the ideal diesel bike will have three cylinders. This for balance and vibration reasons. The same applies to petrol engined bikes.

If you look back to cars, I can remember some fitted with commercial diesel engines back in the fities and sixxties. They were cheap to run but no fun to drive. Diesel engined cars did not catch on until peugeuot made better quieter engines. I think diesel bikes will not catch on in a big way until they too are much more refined. This is what we have to do and I hope I have pointed in the right direction.

I have half a mind to get an Electra with aview to converting it some years down the line when maybe the need will be greater and availability of suitable engines better.