Direto Resistance Fluctuations in Level Mode

[anthonydoud97]

I recently purchased a Direto that I've only ridden a handful of times and haven't noticed any problems in Zwift using ERG mode.

Yesterday I tried it in level mode during a FTP test in Sufferfest and I could feel it changing the resistance constantly and nearly rhythmically - every 3-4 pedal strokes what feels like a change of probably +-30-40 watts.. This is far from my first FTP test, but the first on this trainer, and wow does that small fluctuating resistance make an already difficult FTP test nearly impossible to complete.

So this morning I calibrated the unit using the Elite app and got consistent calibration numbers over three runs (6011. Unit is marked 6015.) Then I tried a steady level 5 300 watt effort in Sufferfest and got the same fluctuations as during my FTP test. I then tried using my wahoo cadence sensor instead of the internal Direto sensor and that didn't help either. Power Smoothing setting in Elite is 2.

Any Ideas?

[Elite Admin S]

Direto has a very precise reading of power and so it continously adjust the resistance to match the target value.
Consider that it is absolutely normal to have 20W differences between a pedal stroke and another.

Please do this test.
Increase the power smoothing (6 for example) and do again the test.
This won't affect the resistance variation, but it affect the visualization of the value and this usually helps.
Give it a try.

[sebrios]

No.
I believe this is exactly what I reported to the team 1 or 2 months ago.
You can almost spin out because of the variation.

Its like if the trainer releases the resistance.
(This only happens to me in some very specific tests that I reported internally)

[anthonydoud97]

Direto has a very precise reading of power and so it continously adjust the resistance to match the target value.
Consider that it is absolutely normal to have 20W differences between a pedal stroke and another.

Please do this test.
Increase the power smoothing (6 for example) and do again the test.
This won't affect the resistance variation, but it affect the visualization of the value and this usually helps.
Give it a try.

The problem I'm having is when the unit is in LEVEL mode. It's not holding consistent resistance. I can feel the resistance fluctuating while I pedal.

ERG mode seems to be working okay.

[Elite Admin S]

@anthonydoud97,

please run my e-training and select level mode.
Please let me know if you have the same issue or not.

Are you connecting using bluetooth or ant to connect?
Are you using a pc or a smartphone/tablet?

[anthonydoud97]

It’s connected via Bluetooth on an iPhone 6s. I can try an iPad if you think it may make a difference.

I’ll test it again later today in the Elite app - thank you for your help.

[anthonydoud97]

I tried it earlier today using my e-training and it seemed better, however I could still feel minor variations in resistance in level mode. I was going to test Sufferfest again, but I was short on time and need to get a good ride in so I just rode Sufferfest in ERG and it worked good however occasionally (every 5 minutes or so) the resistance would suddenly drop off 50-60 watts whithout a cadence change and then slowly come back to normal.

I've got a wired cadence sensor on order to plug into the Direto. It seems likely to me that the fluctuations I'm observing might be the result of the unit erroneously detecting that I have stopped pedaling since the cadence reading I'm getting from the unit is slightly erratic. It's not a showstopper problem, but it is somewhat frustrating.

[anthonydoud97]

Rode again tonight in ERG mode - seems okay, resistance fluctuates a little more than I'd like, but again, I'm fine with it.

Level mode however is an overthought hot mess design wise. I took the cover off to verify what I perceived was happening and yep - I'm not imagining it. Here's what I observed:

Code: Select all

Open My Training APP , open "Trainings", select "level mode".

Start pedaling and the servo drives the magnet into position after a couple seconds.

Keep pedaling and the servo drives the magnet into intermediate settings, floating around occasionally like it's trying to seek a different sector on a hard drive.

Stop pedaling and the servo drives the magnet back into low resistance mode.

Okay, I get unloading the resistance when you're not pedaling, but why did some engineer think it's a good idea to make the firmware try to self calibrate level mode on the fly?

You've got a stepper motor down there with a limit switch. For level mode, you should be doing nothing more than driving the stepper motor to the limit switch on power up, then when pedaling starts, counting motor steps to a certain percentage of your total motor travel that corresponds to the level selected by the user.

I'd love to see a firmware update to address this, but I see they soldered jtag headers on the motherboard which probably means that the firmware is loaded via jtag cable at the Elite HQ (or a different 3'rd party software company) well after the boards are built and therefore a wireless update will never be possible.

Oh well...all in all it's a good unit and I know you're not an electronics company, but really guys????

[henrik]

Have been running not Direto but the Drivo (I) with SimulANT+ and my homebrew Android app using ANT+ FE-C simulation mode and I interpret this to be the same as the Level mode available in e-training. And yes I have also experienced these frequent resistance fluctuations and that the magnets are not positioned as they should must be reason. This is - as already stated - annoying and also adds to extra effort (c.f. normalized power). In some ways this is feature (extra psychological and physical training). And in others like tests this is making comparisons impossible. Or when emulating track cycling with very smooth tracks these fluctuations are really bad!
Not sure on how JTAG headers should be an obstacle to FW upgrades over wireless. Other things might be. Not sure if we ever are going to know what is the problem they have to not get these FW upgrades flying. But very likely there is some kind of HW issue they are trying to work around and might even be succeeding with some X %. But X is still too far from 100...

[francescostudiogiovannini]

Ouch. So sad. Got Direto II from 5 days and I went from a Rampa with a motherboard's damage, refunded under warranty after 30 days. Btw, i have the same bug here, with the Direto II unfortunately. The Rampa instead, once calibrated with an external pm (Stages left in my case, thanks to a friend of mine for that) was immediately spot-on with the power resistance, considering that it does not have a real pm but only a power estimator, sure that it works really fine, so much better feeling the power resistance coherence instead of the Direto. But "what to do to solve that" should be the point.