Café Commando build thread
- Thread starter Jeandr
- Start date
Jeandr said:
Ludwig made the point that the iso's become participants in the suspension process by the fact that the cradle is being pushed and pulled as the rear wheel is weighted and unloaded due to the stock shock angle. This could result in a better damped and planted feel.
I've liked the idea of the Fournales because you might have a better chance of getting the loaded heights equal on both sides with air pressure. If the shocks are unequal it throws the iso's off, and everything else.
There will be some downward loading at the swingarm with this geometry. It's going to be a fraction of the load at the rear axle. The relationship of the distance of the axle to the shock pickup point and the distance from the pickup to the swingarm defines it. Like an upside down scale. I don't know what the bike will weigh but it's probably around 20% of the weight at the rear wheel. With the stock shocks the rearward pull on the swingarm was a multiple of the rearwheel weight, >1.
Jeandr said:
Yes, the steeper the shocks are the less "front to back" force you'll have - but the more "top to bottom" force you'll get. As long as the shocks link the s/amr to the frame they will have an influence on the isoa regardless of which way they are orientated. You just changed the direction of this force.
Actually this leads straight back to BF discussions as it is the other side of this exact story. The BF defines whether the excitation of the whole assembly will be more vertical or more horizontal. Together with the stiffness of the whole system the BF (via the mass forces' distribution resulting from it) defines how the Isos react and from which rpm on the unit runs over-critically (beyond the first resonance frequency that is). So in reangling the shocks you change the vertical and horizontal stiffness of the whole system. Without a proper analysis it is pure guesswork whether that is better or worse in the end.
Tim
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Some times I wonder if yoose guys risk life on joy rides exploring like me.
The rear suspension compression pushes down on the front mount pivoting on the rear. Power pulses to rear tire tend to lift the front, pivoting on rear iso to unload the front mount upwards. Which is more important, and when?
With shocks leaned some don't ya get more travel range d/t the swing arm lever arc?
I now assume, from testing, most motorcycles are more concerned with staying stable leaned on lumpy surfaces than hooking up more power into turns.
So chassis behavior is more importance or over whelms tire grip behavior.
Handling is a non issue on my tri linked Peel, so my fascination with the BF and chassis resonance is how it plays out on hooking up power traction cornering. I get way more bite in power leans on linked Peel than I can on unlinked Peel or Trixie or my modified race tired SV650, which out turns my untamed Commandos even if the Cdo's can out accelerate SV to higher top end. When I mention traction control I mean increasing power straight up so that about any lean breaks tire loose so one steers by tipping bike to skip out and regain thrust by picking it up some, as many times as takes to end up pointed into best straight ahead to scoot into, w/o traction loss. I'm pensive to change factory geometry so all ears to hear how the more vertical shocks get sensed. I can pretty easy move Peel's top mounts and may have to to get a bit less travel d/t fouling stuff.
The rear suspension compression pushes down on the front mount pivoting on the rear. Power pulses to rear tire tend to lift the front, pivoting on rear iso to unload the front mount upwards. Which is more important, and when?
With shocks leaned some don't ya get more travel range d/t the swing arm lever arc?
I now assume, from testing, most motorcycles are more concerned with staying stable leaned on lumpy surfaces than hooking up more power into turns.
So chassis behavior is more importance or over whelms tire grip behavior.
Handling is a non issue on my tri linked Peel, so my fascination with the BF and chassis resonance is how it plays out on hooking up power traction cornering. I get way more bite in power leans on linked Peel than I can on unlinked Peel or Trixie or my modified race tired SV650, which out turns my untamed Commandos even if the Cdo's can out accelerate SV to higher top end. When I mention traction control I mean increasing power straight up so that about any lean breaks tire loose so one steers by tipping bike to skip out and regain thrust by picking it up some, as many times as takes to end up pointed into best straight ahead to scoot into, w/o traction loss. I'm pensive to change factory geometry so all ears to hear how the more vertical shocks get sensed. I can pretty easy move Peel's top mounts and may have to to get a bit less travel d/t fouling stuff.
Jeandr said:
I tried to find out the stock Commando rear wheel travel in the old magazines I have and on the net and came up empty. Plenty of mention of 6" of front fork travel which we all know is barely 4" unless the forks are modified with Greg's kit or the Landsdown kit so I would question any published rear wheel travel numbers. I measured the rear wheel travel on the bike I am building and came up with 6.5 cm (2.5") which is probably in line with most street bikes. If anyone can squeeze their shocks on a stock Commando, I would love to know how much rear wheel travel there is.
Jean
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- Oct 19, 2005
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Don't have to screw one down as I can tell you an over loaded or hard bounced Cdo on ordinary Halgon shocks-springs will rub the rear tire on bottom mudguard, so just measure the gap plus the resting sag. I guess 4" but too wet/cold to trek to shed to check mine tonight. 2.5 inches can work fine for road use if air spring pumped up sufficient.
Jean, I found this, you might want to upgrade your wheels.
http://cgi.ebay.com/ebaymotors/MMW-EXTR ... c95a#v4-31
http://cgi.ebay.com/ebaymotors/MMW-SPOR ... a53e#v4-31
Bigger is better, right?
http://cgi.ebay.com/ebaymotors/MMW-EXTR ... c95a#v4-31
http://cgi.ebay.com/ebaymotors/MMW-SPOR ... a53e#v4-31
Bigger is better, right?
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- Nov 16, 2010
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If you are missing the OE shocks or building a bike out of parts and want an approximate idea of rear travel, just fit the rear wheel into the swinging arm (which needs to be around the full shock extension position), and lift the wheel till it about 12mm from touching the mudguard, and you will then have a good idea of rear wheel movement.
Its very important all these things are properly worked out before buying any parts, or any cutting and welding is started though, as its very very easy to end up with an evil handling machine, which in some cases might also be unsafe.
Its very important all these things are properly worked out before buying any parts, or any cutting and welding is started though, as its very very easy to end up with an evil handling machine, which in some cases might also be unsafe.
Shocks basically done, the bushings are correct, the plates welded to the frame
The coil mount is welded under the tank and the EI will be velcroed and tyewrapped to the little shelf welded to the head steady bracket
With the carburettors to make sure everything fits and there is enough room for the throttle cables
Getting there slowly but surely
Jean
The coil mount is welded under the tank and the EI will be velcroed and tyewrapped to the little shelf welded to the head steady bracket
With the carburettors to make sure everything fits and there is enough room for the throttle cables
Getting there slowly but surely
Jean
Jean, are you new to Jims carbs or have you used them before. The reason I ask is that I have a pair on route. Any setup info would be great.Jeandr said:With the carburettors to make sure everything fits and there is enough room for the throttle cables
Jean
pvisseriii said:
I am as green as you are, on my last build, I used a pair of Kehein FCR35s and to be honest, they are overkill. While the acceleration pump is nice to have, it would constantly foul the plugs until I limited the amount of "squirt" it was spewing on each throttle movement. I did not want to use stock Amals since they wear out really fast, same with MKII Amals, better built, but they leaked and became crappy looking after a short while. I was running out of options if I wanted a pair of carbs and these looked like they would work, at least they were tuned by a Norton aficionado, unlike the FCRs which needed a lot of fiddling (probably still do)
I am sure they will work out, but I did see something that may need to be looked at, the carbs fit well one next to the other, but the air cleaners push them apart. Since this is the first fitting and I did not have all the screws and clamps in place, I will say that for now, it could be a non issue.
Jean
I've done the oif mod on my 1970 Comando and it works fine. The addition of a trident oil cooler and a spin on oil filter makes up for some of the lost capacity when eliminating the oil tank. The filler cap is just behind the steering head with the oil vent tube welded in between the steering head and the filler cap, this line is then connected to a vent tube from the primary cover which also vents the crankcase and a smaller line that hooks into the balance tube between the carbs. The return line goes to the oil cooler mounted behind the fork tubes and below the steering head, it exits the cooler and is plumbed back into the frame on the right side of the backbone adjacent to the filler cap.
Dyo
Dyo
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