Commando Crankshaft Porn

Status
Not open for further replies.
jseng1 said:
Why go to all the trouble when I already have a cam with PW3 profile for BSA lifters - the JS stage 2. Plus it as two improvements - slightly more duration and closer lobe centers. The lobe centers are too wide on the PW3 at 107 degrees resulting in performance loss. The lobe centers on the JS2 are much better at 105 degrees. You want tho lobe centers to be close as possible without causing valve clash - to about 102 degrees but that would cause valve clash on any stock head unless the cam was very mild such as a stock cam (stock cams are at about 102 degrees).
Click to expand...

Yes that`s true and i do considered to order a camshaft from you.
I also believe that you`re making good camsbhaft and will most likely order other products from you.
The thing is i will do some other mods to my camshaft and besides i have learned a lot on the way, i see it as a bonus.
 
Can a single cylinder count as crank porn? It's a Royal Enfield crank

Commando Crankshaft Porn
 
I always heard Royal Enfields usually only run on one cylinder but I never expected anything like this :|

The heading does say Commando Crankshaft Porn though...
 
That looks pretty StarWars Jim.
Do you happen to know anyone with a crank needing balancing? :D

Glen
 
I suppose this means I will be sending you more parts.

Bill G[/quote]

Might as well. On second thought just throw them in the car and bring them down. I will buy lunch. :D
 
Bill G said:
bwolfie said:
Jims buying lunch, hmm. Bill you want to car pool? :lol:
Click to expand...
Google says it's only a 15 1/2 hr drive from my house. Not as bad as I thought.
Bill G
Click to expand...

Need some more persuasion. It's close to 70 degrees here today. :P
 
acotrel said:
I tend to rely on cam profiles and timings for which the power outcomes are known. In Tuning For Speed there is a list of cam timings for various 50s racing bikes. When I think of a commando, I think of the 1959 AJS 7R - the best 350 of the era. As a benchmark I think of t he E3134 Triumph cam. If you fit it to both the inlet and exhaust of a standard Tiger 110 which normally used E3275 cams, and use the factory specified timings, and lengths of inlet and exhaust you get a torque increase right across the rev range, a pronounced cam spot at 4,000 revs and much more top end. That cam is replicated in a lot of very fast bikes of other makes. For a commando with the long stroke, heavy pistons and suspect bottom end it is too much. So in effect I've relied on anecdotal evidence and my own common sense and experience as to how I've timed my 850, and set up it's inlet and exhaust systems. I've advanced the cam 12 degrees to compensate for the back pressure of the two into one exhaust, and open the inlet earlier. However the closing points are not optimal. It seems to work very well, however I believe that is just partially a fluke. As far as profile is concerned, a safe lift rate and closing rate are essential. Triumph GP racers had severe cams and were valve droppers, that is why the E3134 was developed. Ed Iskinderian's polycyclic cams were way beyond me, and I don't know if the theory actually worked in a motorcycle engine. I suggest that lightening the valve train in a commando engine is pretty pointless, it will probably cop 9,000 RPM with our most ferocious cam for a while without causing much trouble, and we never go near that without a bottom end failure first.
Click to expand...

I've read a lot of your posts and now must respond. I do not know why you keep banging on about E3134 cams as though they are the holy-cam-grail! Yes. they were good cams in their day (1950s) but there has been some development since then.

I've raced a few Triumphs, but never with E3134 cams. I'd tend to put them in 'rough and ready' road bike engines where they would deliver a good fun level of road performance, that I agree with.

My favoured racing cam in a Triumph is the Spitfire profile, when combined with offset rocker buttons to alter the rocker ratio, these give .450 lift and strong power, especially from 5,000 to 8,000 rpm. I even ran this combo in a 500 Daytona, although this was a tad 'peaky'.

You don't win races with E3134 cams!
 
For a long time I figured a dynamic balance on a Norton motor was just an extra. I have static balanced many cranks and figured that was good enough. Surely the dynamic balance couldn't be too far off.

When I built the last 1007 motor I did a static balance on the crank and was going to call it good, but I finally decided to take it to my local balancer for a spin. I ended up standing there as he was doing the job. He has a low speed balancer but even at 200 RPM it was obvious that it was off.

To begin with I invested in some soft mounts and set them up with a motor to spin a crank. I could spin it and watch the mounts move and see the vectors with my scope. I can spin a crank to around 2500 rpm.

After spinning a few stock cranks and then the balanced crank from my 880 it became obvious that maybe dynamic balancing was a pretty good idea. Then came the expensive part consisting of the software and balancing electronics.

Here is a little video of a untouched MK3 -850 crank. Jim

[video]https://www.youtube.com/watch?v=pBghyqIBihA&feature=youtu.be[/video]
 
Very informative viewing as the forces build. Makes me think if spun up near red line it'd begin to function like a scout craft's inertial anti-gravity thruster.
 
Jim,
I have had five twin cylinder cranks & a triple crank dynamically balanced over the years, & it has always made an improvement. In the case of an untouched '69 lightning, a night & day difference. Do you think the improvement in dynamic over static would be so great on a billet crank such as your latest project?
Martyn.
 
Matchless said:
Jim,
I have had five twin cylinder cranks & a triple crank dynamically balanced over the years, & it has always made an improvement. In the case of an untouched '69 lightning, a night & day difference. Do you think the improvement in dynamic over static would be so great on a billet crank such as your latest project?
Martyn.
Click to expand...

Yes, from what I have seen so far my billet crank is pretty bad. Jim
 
ludwig said:
A great promotional video .
So , maybe I wàs right to have my crankshafts dynamically balanced 20 years ago ..
Click to expand...

I have usually had my cranks dynamically balanced also. But generally I have questioned the value in it. There is no question the islastic Commando hides a lot of things.

After doing the comparisons I will always balance them. The balancer was a good promotion for me too. Jim
 
Dances with Shrapnel said:
Good stuff there Jim.

I just watched the video and wondered what it would be like if one of those got loose in your shop. :lol:
Click to expand...

Yeah, I thought about that too. The only crank I had spun that fast was the crank from my bike. It just sat there at full speed.

When I was making the video I was wanted to show how much the crank was shaking but I knew it would be hard to see. So I cranked it up -and held my breath.

Before I do that again I think some safety loops might be in order. Jim
 
Status
Not open for further replies.

Similar threads

Peter Waller
Crankshaft primary side end slightly out of true and bent.
Replies
6
Views
821
marshg246
marshg246
marshg246
Rotor (Crankshaft End) Threads
2
Replies
28
Views
4,216
batrider
batrider
jay*mac
commando crankshafts
2 3
Replies
42
Views
5,256
acotrel
acotrel
jseng1
crankshaft bob weight
2
Replies
37
Views
3,838
acotrel
acotrel
S
Crankshaft balance
2 3
Replies
50
Views
5,246
Metisse11
M
Back
Top