920cc Featherbed

Fast Eddie said:
Interesting how the power flattens off at 6,000rpm, my 850 did the same.
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Normally we would see a peak in the power curve, but here the percentage torque drop equals approximately the percentage increase in revs.
Since P (kW) = M (Nm) * n (rpm) * 1/9549 or P (hp) = M (Nm) * n (rpm) * 1/7124 , the power curve remains almost level.

However, there is much signal ripple in the high RPM range. Maybe the engine caused this?

-Knut
 
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Hi Knut!

I've been thinking too long the engine lasts on the street, but I'm used to the engine broken
I think the bolted crankshaft is better than the billet.
I've heard that the billet crankshaft and damage the engine because it does not deflect.
I also put a note that a supplier has removed the billet crankshafts sales, I believe it to be a reason.
I hope that the crankshaft own take, I have to rebalance it, and heaped new high-strength bolts.
But time seems to be.
But you are right that the crankshaft will get tough.
 
Wadefin said:
I think the bolted crankshaft is better than the billet.
I've heard that the billet crankshaft and damage the engine because it does not deflect.
Click to expand...

As an engineer (M.Sc.) I can tell you this is wrong. The deflection causes alternating circular loads on the bearings which of course transplants into the crankcase.
If these loads and deflections get large enough, the crankcases (esp. the drive side) will fracture due to fatigue.
For your engine and crankshaft, it is quite safe to assess these loads and deflections to be substantially higher than those of a standard motor.

An even greater concern is the size of the PTO shaft, which is really tiny for this kind of torque and load transfer. Please have your crankshaft journals and shafts carefully checked for micro-cracking using Eddy Current, penetrating dye and other NDT methods. Another change to consider is fitting a steel flywheel rather than the nodular cast iron F/W supplied by the factory. At 6500 rpm max your flywheel may not be at risk, but fitting one out of steel is one worry less. There are numerous articles on this site describing the virtues of a steel flywheel.

Many used crankshafts are near end of life, and survive only because the associated engines are never revved under full load.



Wadefin said:
I also put a note that a supplier has removed the billet crankshafts sales, I believe it to be a reason.
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This is unfounded speculation. I am not sure which supplier you refer to. There can be a number of reasons for a business to close down or shift its product offerings.
Being pricey (from US$1900 upwards), billet crankshafts will never be a big runner with the average biker, power builders / racers and some dedicated enthusiasts exempted,
and let's be honest, the market for power accessories is with owners of japanese 4-cyl. machines.

-Knut
 
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Okay, Knut.

Certainly you better know metallurgy as an engineer.
My knowledge is not related to the story of the old builders and familiar classic racing drivers.
But, as I said, it was just my opinion / assumption that everyone does in a way, but I appreciate your opinion.
 
Wadefin said:
Hi Knut!

I've been thinking too long the engine lasts on the street, but I'm used to the engine broken
I think the bolted crankshaft is better than the billet.
I've heard that the billet crankshaft and damage the engine because it does not deflect.
I also put a note that a supplier has removed the billet crankshafts sales, I believe it to be a reason.
I hope that the crankshaft own take, I have to rebalance it, and heaped new high-strength bolts.
But time seems to be.
But you are right that the crankshaft will get tough.
Click to expand...

Who was the supplier who has quit offering billet crankshafts?

Ken
 
Good advice, when I had my combat motor done the builder had the crank checked and they found a crack developing on the output shaft. Thanks to his knowledge I didn't waste all that money on the new parts that went into the motor.
 
Hi Wadefin, I am a lover of Commado/Featherbed combinations and love your big build, you have done some outstanding work on your build, one thing I like to know is how come you didn't tilt your motor forward like the Commando instead you went straight up like the Dommie's, just curious.

Ashley
 
Hey Ashley.

The motor is in the stroke because I get a better perpendicular flow to the intake duct. If the engine were tilted, the flow would not be good because the intake duct would have to be turned.
This is just my view of the matter, and I do not know exactly its truthfulness.
 
Hopefully you will find out about my writing.
I have to partially use google as a translator.
 
Wadefin said:
Hey Ashley.

The motor is in the stroke because I get a better perpendicular flow to the intake duct. If the engine were tilted, the flow would not be good because the intake duct would have to be turned.
This is just my view of the matter, and I do not know exactly its truthfulness.
Click to expand...

I had a idea that might have been why, we all have our reasons for doing things whether they are right or not lol anyway you done a good job and your translation is all good.
I built my Commando/Featherbed back in the early 80s and I still love riding it, I built mine on a low budget and the last 7 years have done a lot more improvements not that it really needed it but when I had some spare cash its now the way I wanted it, hope you enjoy yours as mush as I have with my set up.

Ashley
 
Wadefin said:
The compression ratio is 10.63
It starts well, but a bit of heat is a bit difficult.
The cylinder head is stage3, but there is a slight change.
Click to expand...

Generation of additional heat is to be expected when increasing the combustion volume, the compression ratio, and optimizing the ducts and valves for high flow. A percentage of the heat needed to generate that high torque inevitably goes into the head. What to do? There are 3 ways to increase heat dissipation: By thermal conduction, thermal convection, and by thermal radiation.

* Fitting an alloy barrel will increase thermal conduction between cylinder head and barrel. The alloy barrel should preferably be of large fin design. Ideally no head gasket should be used. The alloy will increase heat conduction into the crankcase as well, which acts as a thermal sink. Take a look at the Matchless G45 and BSA BDB34 engines which are examples of this concept. (The G45 had a mated head/barrel joint, btw.)

* Thermal convection between cooling fins and the ambient air may be improved by enlaring the fins and by improving air supply (ducting). Internally, convection between head casting and cooling oil may be improved by fitting a secondary oil pump and enlarged drains from the head. I believe Norton did this on their racing bikes in 1973/74. Fitting an oil cooler will be necessary as the oil pics up a lot of heat.
https://www.accessnorton.com/NortonCommando/increasing-oil-flow-to-head.26731/page-3

* Thermal radiation (electromagnetic radiation) is proportional to the radiating surface and its temperature. The surface colour has little bearing on thermal radiation - a grey casting like colour is fine. Again, fin size and metal composition for high heat conduction matters.

-Knut
 
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The warm-up problems are now in order.
The small carburetor adjustment eliminated the problem.
Knut I am aware of the situation described.
The oil condenser is supposed to be installed when the mail first delivers the order.

Do you have any experience in burning fires and valves?
 
You are talking of ceramic coating of wear surfaces. Coating of the combustion chamber and the valves doesn't make sense as they will be "coated" by carbon deposits anyhow, and prolonged service of coating in this area is questionable. Any coating flakes coming off are likely to damage the exhaust valve, piston and cylinder bore.

Piston coating in the interest of reducing friction and tightening the piston/bore clearance has been applied by some guys here, please apply the search engine on the main page. You may also query member Fast Eddy, who may still run coated pistons.
Application of a coating to limit heat transfer is a good idea only if the piston material is capable of handling the added temperature, which of course means more distortion and the need for increased clearance. Quite a lot of heat is transferred from the piston crown through the (uncoated) piston skirts of an engine, from what I've read. Piston face steady-state temperature is 300 'C, which is about the maximum aluminum can handle. Piston skirt temperature will be about 190 'C while cylinder wall temperature will be about 185 'C.

-Knut
 
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Stock cranks should have the PTO shaft radiused. This is the most likely place they will break and I was able to race them without breaking once they were radiused. The 2nd problem is cracking of the cases on the drive side and you can add a reinforcing plate to fix this. The Maney cases and various aftermarket cranks take care of most of these problems if you gave the money to throw at it. The longer rods and lightweight pistons make a huge difference in reducing stress and with a little prep with the crank and cases as mentioned above you should be OK. But with the HP you're making - keep an eye and check for cracks whenever the motor gets inspected.

My old rusted race crank below which I'm still using on the street.

920cc Featherbed


A plate like below would probably need to shrink fit or use loctite to be tight around the PTO area. Herb Beckers work below.

920cc Featherbed
 
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Hey.

It is now about 1500 km driven by Norton and it works perfectly perfectly.
I believe it will last in a rational way.

And Jim. I totally agree with you.
 
Nice one Wadefin.

Now you’ve ridden it a bit, what is it like regarding vibration?

I just watched, or rather listened to, your video clip in post #4, again. Sounds bloody fantastic !
 
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