Advice please! Meyra Optimus 2

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Advice please! Meyra Optimus 2

Postby DannyB » 16 Apr 2021, 21:28

I have just bought a low miles Meyra Optimus 2 powerchair and took it out for the first time to local woods this afternoon.
It feels odd compared to my previous off-road scooter, as expected. But more serious, the rear rack motor that controls the steering is ridiculously sensitive, so at anything over 40% speed I was swaying about from one over-steer to another in a dangerous series of 'S' shapes.
I still have reasonable manual dexterity/fine motor skills and can control both a computer mouse and the joystick on my indoor chair pretty well. I drove a car for 35 years before MS got the better of me so I'm sure I can grasp the demands of driving the Meyra given time,
I am confident I can get used to the forklift-style rear wheel steering and much bigger turning circle than I'm used to. But I think I need to adjust down the steering motor sensitiviity in R-Net.
If you agree, could you please tell me how to connect up a laptop to the controller and do what is necessary? Please keep it fairly simple. I am mechanically and computer literate but have none of the impressive technical expertise I can see many of you guys have.
Thank you for your time! :)
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Re: Advice please! Meyra Optimus 2

Postby Burgerman » 16 Apr 2021, 21:37

Where to start. You can make it seem better. But if you have any front drive chair with casters or rear steer wheels at the rear you have instability. Theres no way around it, its why the wheels that steer your car are at the front! If you reverse a car at speed and try any kind of steering it tries to swap ends. Thats exactly what your scooter is doing.

You start a turn and the g force pushes the rear wider and the turn tightens up. Which causes more g force that pushes the rear wider still, and so it turns tighter again. Which causes more turning g force... Rinse and repeat. The faster you go the more impossible to go straight it becomes. And the more out of shape the turns become.

Rear steering or rear casters is an unstable configuration. A lot of programming, gyros, and fancy electronics tries to compensate. But ultimately you cant beat physics.
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Re: Advice please! Meyra Optimus 2

Postby DannyB » 16 Apr 2021, 23:05

i hear you and it makes perfect sense. But I can't believe this is just user error and can't be improved... If the stick was less sensitive, at least the inevitable small involuntary movements off centre wouldn't lead to such immediate turns/side to side motion, surely?
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Re: Advice please! Meyra Optimus 2

Postby DannyB » 16 Apr 2021, 23:20

To elaborate, don't the forces you mention only come into play when the wheels are not quite straight?

I need the four wheels to stay aligned when no turning is taking place (and the rear wheels are therefore being pulled even further out of alignment by the forces you allude to).
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Re: Advice please! Meyra Optimus 2

Postby Burgerman » 16 Apr 2021, 23:38

Its not user error. As I say, you can play with settings, reduce turn speed etc or increase gyro sensitivity or increase deadband, to help. And make it much easier to go straight. It should be much easier than with rear caters/tank steer.

But the whole thing really is because you are effectively throwing a dart backwards. No matter how "straight" you throw that dart, it will turn around and fly pointed end first and stick in the board. This is because the centre of gravity is behind the centre of pressure. Like a wind vane. Facing the wrong way.

And you are relying on gyros if fitted, to electrically keep the dart facing in the wrong direction as it flies. Same exact physics. The chair - even in a straight line, wants to swap ends and travel the other way. That you would call backwards. Its worse on a tank steered wheelchair. Somewhat more stable on your setup. But its the same forces all the same.

And all the normal settings we see on a tank steered wheelchair are weird and doing different things on that scooter setup. So I cant really suggest anything that might help. Others with one of those may.
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Re: Advice please! Meyra Optimus 2

Postby DannyB » 17 Apr 2021, 02:15

Thank you. I see that and realise the best thing to do is send it back for a refund ASAP. :worship
Please close this thread so I don't waste anyone's time!
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Re: Advice please! Meyra Optimus 2

Postby terry2 » 17 Apr 2021, 06:41

DannyB wrote:I have just bought a low miles Meyra Optimus 2 powerchair and took it out for the first time to local woods this afternoon.
It feels odd compared to my previous off-road scooter, as expected. But more serious, the rear rack motor that controls the steering is ridiculously sensitive, so at anything over 40% speed I was swaying about from one over-steer to another in a dangerous series of 'S' shapes.
I still have reasonable manual dexterity/fine motor skills and can control both a computer mouse and the joystick on my indoor chair pretty well. I drove a car for 35 years before MS got the better of me so I'm sure I can grasp the demands of driving the Meyra given time,
I am confident I can get used to the forklift-style rear wheel steering and much bigger turning circle than I'm used to. But I think I need to adjust down the steering motor sensitiviity in R-Net.
If you agree, could you please tell me how to connect up a laptop to the controller and do what is necessary? Please keep it fairly simple. I am mechanically and computer literate but have none of the impressive technical expertise I can see many of you guys have.
Thank you for your time! :)



I have one.

It's just a matter of getting used to it.

I go 11 mph on the road with no problems.
But I only use 6-8 mph off road.

Go to an open space and use it.
The joystick is not setup like a tank steer chair. The Meyra is so much better.
Move about at the lowest speed. The boost speed may catch you out for a short while.

And with my 170 AH Lifepo4 cells in, I can do about 100 miles @6mph.
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Re: Advice please! Meyra Optimus 2

Postby rickystyx » 17 Apr 2021, 08:25

I love mine but it did take a little getting used to but also there are ways of altering the steering some of which can cause problems as you seem to be having - they come with a controlled recuction in speed whilst turning and if you remove that it can be quite interesting. Have you changed the settings?
if you send me your settings I may have an idea of what you have that might be causing you issues but rear steering is a bit different
ottobock b400 150Ah lifepo4
Swiss-trac manual chair add on with 30Ah Lifepo4 (want more 15Ah headway cells )
Meyra Optimus (PRIME)2 150Ah lifepo4 :0)
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Re: Advice please! Meyra Optimus 2

Postby Burgerman » 17 Apr 2021, 09:25

The engineer in me would call it something other than different...
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Re: Advice please! Meyra Optimus 2

Postby DannyB » 17 Apr 2021, 22:13

Thank you terry2 and rickystyx. I have decided to send it back although with time I'm sure I could drive it better. I think that having driven it through the woods, in an open field and on the road for several hours, I'm sure it's not for me. But since I'm not wheelchair-bound, at least yet, I want to get another off-road chair with similar specs and chunky wheels, but rear wheel or four-wheel drive (with the option of two-wheel drive and a good range for not too much money, if such a thing exists). :)
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Re: Advice please! Meyra Optimus 2

Postby DannyB » 19 Apr 2021, 17:33

I thought I would replace the bench seat on my TGA Supersport scooter -- which is great for off-road outings with the family -- with a captain's seat, since I could still just about drive a scooter if the seat was comfortable and supportive enough and delay buying a powerchair with a joystick for a while. But TGA want 500 quid for a new seat! unfortunately there isn't a second hand one for sale on eBay at the moment.

Just on the off-chance, has anyone on this forum got a spare TGA Supersport seat in their garage or workshop please? I would happily swap one for the double bench seat if they wanted it.

If I was able, I would fix the bench seat column on to another single seat. But unfortunately I'm not able any more (progressive MS) and don't even have a workshop or tools. To think, back in the day I used to rebuild classic cars, engines etc...
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