Commando Fork Cartridge Conversion

lcrken said:

But, if your riding varies from a single rider to carrying a passenger, and sometimes with luggage, the external preload adjustment is pretty convenient. I probably wouldn't change the damping adjustments for that, but then I don't very often have a passenger or much luggage.

With the basic Roadholder design, I can get the stock forks to work well on potholes or on high speed sweepers, but not both. The modern damper designs are significantly better at that.

Besides, it's a fun exercise in the shop, and another learning experience.

Ken

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+1 on that.

I was wondering when you would chime in, Ludwig! I haven't seen the latest version of your customised dampers until now - they look very neat.

Ludwig is an alien or stealing alien technology to materialize as needed. We've seen his own handy work like mine in that cleaver exhaust cross over butterfly : )

I'm as much or more awed by the all great efforts put into Roadholders as anyone but decided to let the RaceTech guy do my thinking/building for me this time for just a plop plop to install while leaving most the Roadholder guts out. I'm not that good but boy howdy the varied Ozarks is and building a Cdo meant to learn forced hard way so propose lending me various guts and instructions to compare which I like best by least crashes, most comfort and best times on various test tracks from front yard flat track, Graveled commutes and ground zero for elite sport bikes struting their stuff. My brief manic episodes imply to me that any and all forks are innately dangerous and varuiys effective kinds mostly determine what pilot must do to compensate similar to tire temp and compound and air and size - no one combo is always optimal through some forks can protect inept pilots or surprise conditions/maneuvers. Chew on it as figure i've ~decade to get maniac cycling out my system before settling on a side car fork. Peel gets fancy performance logging gizmos with suspension dyno on either end if needed. Ludwig inspires trim slim linkages to do this besides pressure zones pulsing data.

Gravel with graded size stones and washboards w pot holes in sweepers and braking zones on off slope crowns really reveals importance of the speed of valve function action per spring-fork travel oscillation not matching ground texture or tire adhesion hysteria. Asymmetric slightly conflicting over lapping leg valve functions makes all the sense in this world. Only way I know to compensate semi predicable is go rather sane slow or a bit too much so forks are not the main steering factor. Screams/Language/Loudness of noises under helmet are my main feedback. Its transition zone between going too slow or not fast enough that's always a mystery.

Steve,

I didn't know RaceTech would do anything for Roadholders. What sort of mods are they going to do? I know you can make their emulators fit, but you have to give up the damper rod and piston to do so. More details, please.

Ken

Ludwig.
I hope that nylon piston ring doe's not slide up the stanchion bore? The surface finish in the ebay Indian made tubes will cut it to bits in 5 miles.

My own digressive valves with OD seals work well in AN Stanchions as they have a good internal surface finish, it looks to me that Ludwig's version is better still and the valve runs in his alloy damper body. Who would buy tubes off ebay made in India and also be fitting digressive dampers of their own design or adapted ?

The stanchion thread as been discussed many times,"who would buy cheap Ebay stanchions?" proberly a few, £54 as opposied to AN £145 . I personally know a guy who bought a £3000 gearbox ,then some indian stanchions..but as you say who would fit bespoke digressive dampers into cheap stanchions?
I also know a guy who use's ebay stanchions in his £30k Manx..£100 cheaper as some clout!

kommando said:

My own digressive valves with OD seals work well in AN Stanchions as they have a good internal surface finish, it looks to me that Ludwig's version is better still and the valve runs in his alloy damper body. Who would buy tubes off ebay made in India and also be fitting digressive dampers of their own design or adapted ?

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I'm semi aware why Race Tech emulators not mentioned much for Roadholders and more so with Ludwigs feedback so may experiment with emulator in one leg and something else in other leg but mainly for sense of functions I might be missing out on - as I recognize the annoyances-limits mentioned in other forks but so far I've nothing I know of to solve in hobot forks but the chopper looking stance. I'm glad I got the 6" travel solved and severe stout spring last inch of travel but don't seek being a fork designer just a pleased pilot so who knows the best route yet on or off pavement. Ponder this sales pitch

http://www.racetech.com/page/title/Emul ... ng%20Guide

I use reverse fitted racetech type valves in BSA and Triumph forks pre OIF and do not get the cavitation that Ludwig gets so can use them as a rebound damper.

The differences in design that may cause the lack of cavitation are

1. The valves are fixed in place in the stanchion instead of sliding up and down inside, you can do this on forks with external springs unlike the Norton with its internal springs. The position is above any holes in the stanchion for oil transfer.

2.The damper valve is completely eliminated and replaced with a short section left 1.5" long in the bottom to act as a compression bump stop.

3. BSA and Triumph forks use double lipped fork seals not the single lipped used by Norton.

4. I use dowty washers on the bolt underneath holding the bump stop in the bottom of the leg.

5. The porting is changed with the low speed port at 1 mm instead of 1.5 mm

6. The seal on the OD is an X ring but is static not sliding.

No idea if any, none or all of these help but draining the oil after a run over rough ground shows clear oil with no bubbles, I know the rebound damping is active from the ride.

One of these days I will try it out on a Norton but with double lipped fork seals, dowty washer but use a sliding seal and internal springs and check to see if it cavitates.

Hm I know forks can allow a wild sweeper to feel like crossing a plowed field diagonally while pilot fighting for life praying it won't get full sideways to the ruts or hi side city. Ya see this in the wiggle jiggle of IOM and such. Not all the jiggles onset from front of course. I forgot why one couldn't just flip an RT over but kept in mind I might want to put cap/damperrod/piston 'valve' back in one side. There were some clever British upgrades on the factory caveman valve I'd intended to mimic but never got aroundtoit. I don't know what I want only what its like w/o forks taking away any attention and it leaves a lasting hi. Ya seen my tractor tires as off road scares me the most and hope loosing or tighting the spring rates might ease fork dampening needs. Who will be first Commando on the block with 'puterized active suspension? Oh yeah, just in case, there are occassions when giving the gun can save a front wash out. oh YIKES!

kommando said:

I use reverse fitted racetech type valves in BSA and Triumph forks pre OIF and do not get the cavitation that Ludwig gets so can use them as a rebound damper.

The differences in design that may cause the lack of cavitation are

1. The valves are fixed in place in the stanchion instead of sliding up and down inside, you can do this on forks with external springs unlike the Norton with its internal springs. The position is above any holes in the stanchion for oil transfer.

2.The damper valve is completely eliminated and replaced with a short section left 1.5" long in the bottom to act as a compression bump stop.

3. BSA and Triumph forks use double lipped fork seals not the single lipped used by Norton.

4. I use dowty washers on the bolt underneath holding the bump stop in the bottom of the leg.

5. The porting is changed with the low speed port at 1 mm instead of 1.5 mm

6. The seal on the OD is an X ring but is static not sliding.

No idea if any, none or all of these help but draining the oil after a run over rough ground shows clear oil with no bubbles, I know the rebound damping is active from the ride.

One of these days I will try it out on a Norton but with double lipped fork seals, dowty washer but use a sliding seal and internal springs and check to see if it cavitates.

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Kommando - this is your solution, isn't it? - http://www.b50.org/phpBB2/viewtopic.php?f=5&t=5232

ludwig said:

I tried Race Tech emulators , but they are useless in Roadholder forks .
With some mods you can get them to do compression damping , but not rebound .
but I do like the Racetech idea ( spring loaded valve ) for degressive damping .

The setup with the nylon piston ring ( basically an inverted emulator ) was a failure, not because of the piston ring , but because of cavitation .

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Ludwig - what is the reason the Race Tech valves gave compression damping but not rebound damping in Roadholders? Do they need to sit atop damper rods on spacers to work properly?

And why did your earlier design cavitate?

I converted a set of forks on my BMW racer to Racetech Emulators. Drilled out the holes in the damper rod and added two more 6mm holes thus disabling the compression.
The emulator sat on top of the damper unit with suitably machined spacers below and above.
Springs I think were .85kg/mm and 10 wt oil to 100mm below the top with springs out and sliders pushed up.
I found it worked well, better than my mates BMW with 'progressive springs".
I did notice pattering at over 160kmph and larger bumps ( yes our tracks have bumps)
Fast forward a year and I got talking to the local Ohlins Service guy who does lots of race bikes.
He was not excited at the prospect of a BMW :roll: but suggested Ohlin 36S rear shocks and take a look at the front end.
He fitted .95kg/mm springs and I assume Ohlins fork oil. He says you can't use W to measure fork oil as its not like an engine.
Also said that with only 170Ml capacity of oil the emulators were going to cavitate.
Set up the front and rear to 30 mm static sag and went racing.
I put a cable tie on the front and rear and found that total travel was about 70mm at the front and 60 at the back.
Works very well and confidence building. I can get up to about 200 kmph on the track and no pattering or shake.
I raced a 1935 mk 5 Velocette KTT 350 around the track in pre war and man, respect to those guys in the 1930's, they had nads of steel. :shock:

Based on my lack of cavitation in external spring forks and the Ohlins guys recommending more oil this cavitation issue is due to on the Norton the valve having to be high up on top of the damper body close to the top of the oil level. On the external spring version the valve sits close to the bottom of the stanchion and is fixed in position so the valve moves downwards with the stanchion and not upwards inside the stanchion so it is always well covered in oil. So the potential cures are external springs with the valve fixed in the bottom of the stanchion or filling the compression leg with more oil. Only an experiment will confirm.

Trixie's factory Roadholders only real concern [at the rates I limit her too] is sometimes hard braking causes the tire to hop/skip/chatter/chirp/lock so must let off way more than desired. What sort or phase of dampening is applicable or not acting right?

hobot said:

Trixie's factory Roadholders only real concern [at the rates I limit her too] is sometimes hard braking causes the tire to hop/skip/chatter/chirp/lock so must let off way more than desired. What sort or phase of dampening is applicable or not acting right?

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All I can say is that I experienced what you have described on several bikes. One - a Honda CBR400RR track bike years ago - had springs that were too soft, so the forks tended to bottom out too easily under hard braking, leading to a few 'moments' where the front tyre would skip enthusiastically towards the kitty litter instead of biting before turning in. The low speed compression damping could also have been poor. End result: I had to back off earlier than I should.

The other - on the Seeley I ride now - in the last few years has shown a tendency to skip when hitting a change in surface while cranked over, or at the start of the braking point where there are ripples in the tarmac caused by race cars. This also led to a few 'moments'. I put this down to the absence of valved high-speed compression damping, where the fork locked out because the oil couldn't escape through the orifices in the damper rod fast enough. It may also not have been helped by wear in the slider, which can cause binding and stops the suspension sliding smoothly. Again, I had to back off earlier than I should. This is why I want to get that sorted before I fit the cartridges for real.

If you can measure your slider bores accurately, John Bould may advise on the wear limit that is acceptable.

Dang daveth your remarks leave me unpleasantly stirred at your fork fright modes but more informed on Trixies factory fork faults. Trixie forks are worn factory internals and do ok taking up rough unpaved routes and paved lumps so nil dampening restriction which leaves weak spring bottoming as most likey brake hair raiser. I crashed Peel 7 times 1st 5 days owning and SuVee twice in 1st month all d/t ***slight*** brake use going a bit over walking speeds or a couple mph slower than sight seeing waking pace when front WHEEL WAS NOT PERFECTLY INLINE FULLY UPRIGHT VERTICAL. I've crashed a few more times on SuVee going mid 30's behaving to get home straight ahead to hit seriers of seeming 3 minor pot holes that apparently packed the forks down to coil bind so last hole bounced both tires off surface & cycle twisted in air some to land at a lean with me under it tearing up hip/knee/ankle joints. These events hit so fast at such mild rates I really didn't know what went wrong but my stupid desire to ride cycles. I don't want to modify factory Trixie using non Norton part numbers but would consider slicing off some factory spring to stick in a stouter spring section if allowed better in line braking as its sudden hazards that scares me to maxium brake but even so my hand feels like griping a Red Hot Rod Whitch Test on brake lever so 1st reflex is brakeless steering around if at all possible as would rather crash into ditch or fence than slide under tractor, cattle or trucks. As for trail braking while leaned best wishes surviving that bad habit that is TABOO to me.

One vital factor I've learned reading this thread and then more online seraching is the rebound-expansion damping is always only the same spring rate force/speed so its less complex to accomadate than the road slaps of compression dampening, which implies - fancy multi stage compression valve for compression control and just oil grade and holes for rebound resisting. Race Tech says set emulators compression dampening with spring screw adjustment and just fiddle fluid grade &or damper holes for the rebound.

After almost 1,000 miles on the forks, I thought it might be time for an update. Bottom line is that the front end feels much smoother on a variety of pavement, from smooth to pot-holed, and the shortened Ninja spring seems about right. I rode it for the first 100 miles, and my grandson for most of the rest, mostly at the rally. The only adjustment we made was to increase the pre-load a bit. I weigh considerably more than he does, but he rides more aggressively, with the result that we're both happy with the same pre-load setting. With the original pre-load setting, he did experience some front wheel skipping under very heavy braking. It seems better with more pre-load, but I need to do some more testing to be sure. I'm planning to play with rebound adjustments, just to see how much effect they have, but the original setting at half travel seems to work well, so I don't know if I'll see any improvement. Now I just need to find replacements for the clapped out Girlings on the rear.

Ken

Good to see your update, Ken, and all good news. It looks like it was worth all the work.

My Seeley had its first outing on track last month with the Yam R6 cartridges. I found that with the specified 5wt oil, I had reached the limit of adjustment before I got enough rebound and compression damping. There was no wheel skipping, the ride was smoother over ripples, and the bike behaved itself enough that it allowed me to just get on with riding. Now the forks have 10wt oil and I will see how they work at my next track event. So, more tweaking needed but overall it was worth doing.

daveh said:

Good to see your update, Ken, and all good news. It looks like it was worth all the work.

My Seeley had its first outing on track last month with the Yam R6 cartridges. I found that with the specified 5wt oil, I had reached the limit of adjustment before I got enough rebound and compression damping. There was no wheel skipping, the ride was smoother over ripples, and the bike behaved itself enough that it allowed me to just get on with riding. Now the forks have 10wt oil and I will see how they work at my next track event. So, more tweaking needed but overall it was worth doing.

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Re; "Now the forks have 10wt oil"

Should have gone to 7.5 weight oil first :!:

Bernhard said:

daveh said:

Good to see your update, Ken, and all good news. It looks like it was worth all the work.

My Seeley had its first outing on track last month with the Yam R6 cartridges. I found that with the specified 5wt oil, I had reached the limit of adjustment before I got enough rebound and compression damping. There was no wheel skipping, the ride was smoother over ripples, and the bike behaved itself enough that it allowed me to just get on with riding. Now the forks have 10wt oil and I will see how they work at my next track event. So, more tweaking needed but overall it was worth doing.

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Re; "Now the forks have 10wt oil"

Should have gone to 7.5 weight oil first :!:

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You might be right, Bernhard. First impressions of low speed rebound in the shed feel good with the 10wt We will have to see when I test it and I will let you know!

lcrken said:

After almost 1,000 miles on the forks, I thought it might be time for an update. Bottom line is that the front end feels much smoother on a variety of pavement, ..................... I'm planning to play with rebound adjustments, just to see how much effect they have, ............Ken

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I've been following this thread ,thanks for the update Ken. One of the guys that I work with has a little used sporster front end that I can get for cheap, so I was curious about your results. I fitted the front end from a honda hurricane 1000 to one of my old Cb750F's years ago. I need to research the harley some more to see if it is worth my time and effort to set it up on my MKIII. Anyway thanks for posting