BEAMts Torque Sensor...Figured it out!

Triketech said:

Any updates on the Beam TS?

No one seems to have them in stock, so I sent the OEM an email to acquire one for testing.

Click to expand...

Everything about the BeamTS seems to have all but died, which sucks. With that in mind, it would be nice if this forum could host the BeamTS software that Avitt has, as I'm having troubles finding it.

Speaking of which, Avitt, I'm going to message you!

And still a mystery product. No one seems to hve them, and all software links are dead ends.

Hi there,
I am trying to design a torque sensor, similar to Beamts. However it is not clear to me how stiff the flexure has to be. Should it flex fully under full rider’s weight (rider standing on pedal) or it is going to be too stiff? Any ideas?

I know these are not really available but I got lucky and found one locally. It’s the prodecotech version and mounted it on a tadpole trike and hooked to cycle analyst. It’s easy to wire to the throttle but you can’t configure anything so I got a 24 pole slim pas sensor from grin and added the torque wire from the beam to the pas plug pin 5. Only other trick is the beam wants 5v so you also need +5v from the throttle input, not the 10v from the pas plug. So basically the ca thinks a torque sensor with cadence is hooked up but in reality the ouputs of the cadence and beam are being combined so to speak. Works great so far actually and reads the true torque off the chain. Also the cadence sensor adds some safety so that you have to have actual rotation to get output. Anyway figured I’d throw this in the mix in case anyone has one lying around, pretty good solution.

vmbray, Fantastic bit of engineering -- and a good find on your part. I'm doing something similar, except that instead of using a BEAMts, I'm getting my torque signal from strain gauges I've placed elsewhere on the bike. Your use of the new 24 pole PAS sensor from Grin sounds like a great idea.

Could you by any chance post the PAS and Torque settings that you're using in your CycleAnalyst (CAv3) setup file? (as well as the firmware version you're currently using on your CAv3). Actually, more details on your entire build would be extremely interesting. Thanks!

vmbray said:

...so I got a 24 pole slim pas sensor from grin and added the torque wire from the beam to the pas plug pin 5. Only other trick is the beam wants 5v so you also need +5v from the throttle input, not the 10v from the pas plug.

So basically the ca thinks a torque sensor with cadence is hooked up...

Click to expand...

A nicely resourceful solution to get all the signals needed to make the CA happy
Well done!

Thanks guys! I'll try to post up some build pics when I have a few mins.

For the settings you can start by setting the sempu and then change the type to custom trq, this will get you set as 24 poles, 2 wire, reverse polarity. Currently I have 15.0 Nm/V set, I hung an 8 kilo vise on the crank and after some questionable calculations ended up with that, it seems reasonable but I thought it would be higher. Maybe the 34 tooth chainring is at play here. Planning to hang a heavier dumbbell on it and see if it results in a higher number. Zero torque is at .95v, pas mode torque of course, start level 5 watts, scale factor 4.0 w/hw, pas asst avg is 12 poles. Start/stop at defaults.

Also I have a digital aux that is set for five levels, at the highest setting pedaling pretty hard uphill I can get around 600 watts from the motor which seems safe. The ultimate goal is to get a bit more speed for a given effort, without reducing the effort. Plain cadence doesn't really do this since the more you spin, the insanely faster you go. As a go cart it rocks but for getting exercise not so much. It made me wonder if it would actually be a great option in the CA to have a plain cadence mode where it reversed it's output so that it gave more assist at lower cadence and tapered it off as cadence increased. Not sure if that would really work.

Edit, hung a 40lb or approx 18kg dumbbell on the crank arm, cranks are 165mm. If I'm doing this right, I get 18kg * 0.165m = 2.97kg-m, and 2.97kg-m * 9.8 = 29Nm. The CA is reading 3.2V, so the difference from rest is 3.2v - 0.95v = 2.25v. Then 29Nm / 2.25v = 12,88. I got right at 13 Nm/v using the lighter weight as well, and I just entered 15 since it seemed low based on what I've read, but again it's a 34 tooth chainring so that has to play into it I think. Am I doing that correctly? Oh also it's CA 3.1 b21.

vmbray said:

It made me wonder if it would actually be a great option in the CA to have a plain cadence mode where it reversed it's output so that it gave more assist at lower cadence and tapered it off as cadence increased. Not sure if that would really work.

Click to expand...

It already does that in the basic cadence mode. You can use a larger Start level and a negative RPM scale factor. This gives you a boost off the line then assist tapers back as you come up to speed.

Thanks vmbray, that's some very useful information!

Here's some build info and pics https://endless-sphere.com/forums/viewtopic.php?f=6&t=94410&p=1382414#p1382414

For people like me who ended up on this thread looking for a Torque sensor solution when the bottom bracket is not an option, and then found out the BeamTS is no longer available, I recently built a custom Torque sensor using a load cell and amp, and successfully combined it with the throttle for a great Torque Sensor pedal assist experience on my BoxxBike.

Below are the threads detailing what I did in case it can help someone else

Early tests:
https://endless-sphere.com/forums/viewtopic.php?f=3&t=94174&p=1684543#p1679413

Wrap-up:
https://endless-sphere.com/forums/viewtopic.php?f=3&t=94174&p=1684543#p1686510

And the Summary Document
https://onedrive.live.com/view.aspx?resid=4BE668230430EFDD!2790&ithint=file%2cdocx&authkey=!AJJC5hfnmnV612M

Thank you for posting this.

When I someday get back to my Nano Tidbits thread, it's probably going to help me do the torque=sensor-only startup I need for the SB Cruiser trike (it works great as cadence-only once I'm rolling, but it sucks starting up because it's heavy (especially loaded with cargo, groceries, or a st bernard) and my joints don't handle that stuff very well anymore.

(I usually use a throttle burst to get going but I'd rather not do that as sometimes it's more power than I want, because have to slam it on as gradual increasing wont' always startup, but instead just stutter and grind and then the controllers shut off until I let the throttle go. When I slam it on, sometimes it's way more than was needed and the trike surges forward. That is not safe when I'm in traffic or in some other situations. :/

Hi, is anybody able to share or point me to a copy of the software, I can't find it anywhere to download any more. Thanks!

Which specific software?

You may be in luck.

At the time I was looking for a BeamTS sensor, I downloaded all I could find, and I tend to keep all the SW I download

I posted what I have in the online folder below, there are two Zip files that may contain the sensor software you are after (I hope)

https://1drv.ms/u/s!At3vMAQjaOZLlWzLk8yLggvXRplD?e=dJ0bRC

Very lucky (it was the config gui I was after) - thanks so much!