T-50CM2 non-symetrical CAM behavior?

[THXT01A]

I installed the non-center, non-linear cams with the heavy springs in my new T50CM2 base. I also have the "tension" screws all the way down to give the heaviest spring tension. I noticed something strange--that the both axes have non-symmetrical force to get to the extremes (i.e. it's easier to move the stick fully to the right than fully to the left, and easier moving it fully forward than fully backwards). I noticed that the cams themselves weren't symmetrical. Is this supposed to happen or is there something wrong with the base/cams/springs? It feels quite strange that the resistance is uneven depending on direction..

 

-Sticks

[HC_Official]

CM2 CAM's should feel symetrical .... unless you are using externsions and or have the grip angled off centre

[Goblin]

I noticed this too.

What I think is happening is that the spring is compressed beyond the linear region of compression, when the spring is tightened close to max.

Try to unscrew the spring tension a bit.

[THXT01A]

Thanks all for the responses.

 

HC_Official--I took the extension off and made sure the grip wasn't off center.

 

Goblin--I tried loosening the spring a bit. It made the effect slightly less noticeable, but is still there.

 

Any thoughts why the tightened spring would have this asymmetrical behavior? I figured it would be compressed equally at both ends of travel.

 

Is this something that could be fixed with filing away one side of the CAM since it's longer and is more curved? I understand the progressive resistance created by the curvature, but the CAM range of travel is longer on one side than the other. Not sure why that is.

 

I've reached out to Virpil about three weeks ago and opened a ticket, but haven't had a response although it said the usual turnaround time is 24-48 hours.

[Eagles787]

I noticed the same on mine, and when you open up the device you can clearly see why. The Cam system is not symetrical, and I found this quite a bad design for such a device. The roller bearing traveling over the Cam moves either closer or further away from the pivot point of the arm that compresses the spring. To make this feel more linear, Virpil made the curve of the Cam asymmetrical to compensate for this. Even though the spring is now compressed the same amount in both directions, the way the spring force is transferred to the stick is still asymmetrical due to the different arm length to the pivot point. Hope this makes sense some how, if you open up the base you can see how this works. Unfortunately this is just how it is designed, and can't be adjusted by the spring. I tried initially the heavy springs as well, but the greater spring force makes this asymetry more pronounced. I went back to the standard medium ones and makes it less noticable.

[GriffonBR]

That's the same feel that I always had with the first version (last batch). Recently I sold my old one and got the WarBRD base that IMO it's way better in terms of precision and I don't have to use extensions anymore Maybe the WarBRD gimbal design eliminates this because now I don't notice the problem.:)

[Eagles787]

GriffonBR, you are exactly right. The WarBRD gimbal uses dual Cams per axis, one per direction, a much better design. This keeps the forces symetrical. I bought the CM2 as it was recommended for use with an extension. However with an extension and the heavy springs, this asymetry of the CM2 is quite bad. I have to use it now with light spring force to make it usable.

[Goblin]

Arjan, have you tried the kosmo sim cams? I feel they are better suited for heavy spring loads.

[Eagles787]

I use the non center cams that were provided together with the CM2, not sure if those are Kosmo. However the asymetry comes not from the cams, but from the design of the gimbal. With the heavy springs this asymetry becomes quite noticeable unfortunately.

[THXT01A]

Thanks for the responses all. I noticed the asymmetry of the cam length as well and could see exactly when the far left "bump" occurred where you needed exponential force to get the stick to full deflection. Since the cam was shorter on the other side full right deflection was easy-peasy. I thought I was being persnickety after having spent that much on something with great reviews, but at least I know it's not that my unit is defective but rather an engineering defect which gives me peace of mind by having an answer.

 

I still wonder if you could file down the cam to eliminate that asymmetry?-- Would need machine precision but could it be possible?

Edited January 25, 2020 by THXT01A

[Goblin]

I use the non center cams that were provided together with the CM2, not sure if those are Kosmo.

 

The preinstalled cams are the Avia-sim soft center cams.

 

However the asymetry comes not from the cams, but from the design of the gimbal.

 

Well, yes and no. The design of the gimbal creates assymetry but the cams are supposed to compensate for this, as well as regulating the spring force along the stick travel. This is why the cams are assymetrical.

The Avia-sim cams seems to have an irregular compensation in one direction, but the kosmo cams does not.

[wolfstriked]

OMG I was about to order a CM2.No thanks man,I am not gonna file stuff down to make it feel symetrical at high tensions.I will now gladly stick with my warbrd ;)

[VpR81]

OMG I was about to order a CM2.No thanks man,I am not gonna file stuff down to make it feel symetrical at high tensions.I will now gladly stick with my warbrd ;)

 

Same in green here. Got a Warbrd for sidestick and a TM center mounted. I wanted to switch to a T50 within the next months, but i assume i will have to regrease my TM base a couple of more times while waiting for a CM3 (wich will hopefully fix that design flaw) to be available...

[Eagles787]

The preinstalled cams are the Avia-sim soft center cams.

 

 

 

Well, yes and no. The design of the gimbal creates assymetry but the cams are supposed to compensate for this, as well as regulating the spring force along the stick travel. This is why the cams are assymetrical.

The Avia-sim cams seems to have an irregular compensation in one direction, but the kosmo cams does not.

 

My CM2 came with pre-installed centering cams with a strong centering notch. I swapped them for one of the supplied extra cams that had no center notch, I don't know the name as mine came not labelled or anything. But it was the only suitable one out of the supplied set of cams.

 

Yes and no, the assymetrical cams create an equal compression stroke on the spring in both directions, but the way this spring force acts on the stick is still assymetrical and this is what you feel I think. Maybe this could be improved by a more complicated cam shape, but doing this by hand would be complicated I think. I fly real world aerobatics and use the stick for memorising routines on the sim, so symmetry and stick force is very important for me. However real world stick forces are much higher, and I would have preferred to be able to use a stronger spring action on this stick.

[Goblin]

but the way this spring force acts on the stick is still assymetrical and this is what you feel I think.

 

That doesn’t explain why I don’t experience assymetric forces with the kosmo sim cams.

 

Have a look at my review and at the pics of the cams a bit further down. Were there no ”two hole” cams with your MT-50 CM2?

 

I fly real world aerobatics

 

Cool! What do you fly? I got my aerobatic license, but I haven’t practised the art in almost 20 years. Just flying to eat (and buy expensive flightsim controllers :helpsmilie:) these days.

[Eagles787]

Goblin, i checked my stick and i have right now the avia sim cam installed with no center and the medium springs. These still have a slight asymmetry but not as bad as with the heavy springs. I will try your suggestion and change to the kosmo sim with no center and the heavy springs.

 

I fly Extra and Pitts for fun and airliners to pay for these hobbies :pilotfly: But hard to get the free time, so recently started DCS and Aerofly in VR to get some extra practise time, waiting for the Extra 330SC to come out for DCS :joystick:

[Goblin]

I will try your suggestion and change to the kosmo sim with no center and the heavy springs.

 

I’m interested to hear what you think of those...

 

But hard to get the free time

 

Nobody’s selling 28 hour days... I’ve checked. ;)

[driftaholic]

I have the same issue with these cams. I posted on their forums:

 

https://forum.virpil.com/index.php?/topic/1306-problems-with-non-linear-no-center-avasim-cams/

[j9murphy]

I was getting ready to buy a new base and thought it was going to be the CM2.. for those of you that already have the CM2, what would you recommend buying at this point? Get a WarBrd? Switch to VKB?

[JoeyJoJoJunior]

I have the same issue with these cams. I posted on their forums:

 

https://forum.virpil.com/index.php?/topic/1306-problems-with-non-linear-no-center-avasim-cams/

 

Hmm you mentioned if it's the 1 cam per axis. The VKB T-Rudders have the same issue for the same reason. Pretty annoying.

[driftaholic]

Hmm you mentioned if it's the 1 cam per axis. The VKB T-Rudders have the same issue for the same reason. Pretty annoying.

 

They must be miscalculating something because my Slaw device rudder uses one cam and it's offset so it doesn't have a symmetrical cam design and has perfectly equal forces. I'm gong to bring a spring scale home and see how far off they are.

 

The biggest bummer is Virpil isn't really communicating on this. I'll gladly buy updated cams.

[Ashcroft]

I don't believe it would be possible to have exactly equal forces on each side of an axis because of the design that uses a spring on one side and pivot point on the other. Its effectively like pushing on a seesaw close to the pivot point and then further from it, one just gives more leverage. At the same time the end with less leverage has to move the spring through a larger degree of motion.

 

Those things combined would be near impossible to balance with cam shape alone.

 

Its one reason I preferred the look of the Warbrd system. I guess they thought it necessary to achieve the ability to use long extensions and heavy grips.

Edited February 18, 2020 by Ashcroft

[driftaholic]

The funny thing is it's the side with more leverage on the spring that shows the additional force. It literally could be re profiled as a solution. It's totally possible but without their drawings it's not going to be me who figures it out. It's not like it's off by a small amount. If I had to guess this is like a 10-20% difference. Furthermore it's not a symptom shown by the soft center ava sim or either of the cosmo sim cam profiles, that alone is enough to logic my way out of thinking it's a design flaw of the asymmetrical cam.

[THXT01A]

I'd be curious what the results of the spring scale are.

 

I've moved on and installed the linear/no center cams in the x axis and the previous "bump" at 80% travel is now extremely muted.

 

With the linear cams the force required to move the stick is a little interesting because it isn't truly linear and has the asymmetry as well. If you deflect the stick a little left (30-40% of travel), there's little resistance but the remaining travel requires slightly more force. The movement to the right is the exact opposite. the first 30-40% of travel requires more force than the remaining 60-70%. I'm not a physics guy/engineer so I'd chalk that up to the single cam per axis as other more qualified users have stated, but--I can't help but think that you could design the cam with some CAD software to negate these effects. The cams themselves are asymmetrical in design for a reason-- maybe they just weren't machined and designed the right way?

[driftaholic]

They could add a load cell to one of their test examples in the lab and plot it against the encoder values.

 

Either way, I'm a bit more optimistic this will be solved by Virpil. I've made contact and they were eager to solve it.