High angle & Displacement 6DOF

[DoctorD]

Well...
I think I'll be dreaming of metalwork, cutting, grinding and drilling for some nights to come
I've managed to put a good amount of time into the framing components for the remainder of the platform, with the following image the result:

CutSectionsLowISO.JPG (178 KiB) Viewed 6365 times

I am now also the proud owner of some fantastically made stainless steel torque arms and RV90 size gearboxes:

TorqueArmHeld.JPG (130.23 KiB) Viewed 6365 times

Drivetrain.JPG (134.16 KiB) Viewed 6365 times

I'm absolutely aching to finish up the frame (welding, drilling, priming and painting to go) in readiness to start testing Thanos' electronics

[Riton]

very nice
ready for welding

why did you not centering the drilling on the tubes?

[DoctorD]

Heya Riton, thanks for the comment.
I think you are referring to the 20mm drill holes in the blue steel sections?

They are offset so that my upper platform bearings and control rods miss the outer edge of the platform at high tilt angles.
Have a look in the following picture. Hopefully this answers your query

OffsetExplainText.jpg (95.01 KiB) Viewed 6362 times

[Stevant1]

Hey Doc,

I have a 1hp motor going into a 60:1 gearbox, similar to trip's setup. Same manufacturer actually. The length of my arm is 160mm from center of the gearbox shaft to the center of the ball joint. What kind of weight do you think I'll be able to carry on my 6DOF platform? Sounds like you have the formula for this.

As always, Thanks!

Stevant

[Riton]

I am not sure understanding.
I would see in operation.

This is a safeguard, that's it.

engines by the soft going well limit the angle?

[DoctorD]

@Stevant1
Your gearbox has a maximum rated output torque of 1670 Inlb (189Nm) for a 1hp motor configuration (from the manufacturer's specs). If you use a 0.16m long lever arm then that equates to a maximum force of 120kg at the end of each lever arm (when the lever is at the full horizontal postion). For example, this will be at the 'worst' when you have the platform surging/swaying over a single lever arm. This will mean that a greater proportion of the platform payload will be suspended over a single lever arm/gearbox/motor assembly than for any other postion. The ratio of this shift of total weight will depend on how closely you have spaced the base mounts relative to the upper platform connection points (the further out the bottom is to the upper platform the less this shift will be).
Without knowing your exact platform geometry, the offset of your platform load and the aggressiveness/frequency of the motions, it will be hard to tell you exactly. But I would say the max/optimum payload would lie somewhere between 200 to 400 kilo's. You could probably go more, but it will have an increasing affect on the scope of motions you can expect (lower frequency, less severe, etc.) and also possibly start to really stress out your drivetrain and components.
Hope this helps
DoctorD
P.S. If you could shoot me some scaled pictures of your plans I can do a dynamic analysis for you (and get to within 10% of your max payload)

[TripRodriguez]

Thanks DoctorD!

I'm building my platform with the same motors, gearboxes, inverters, and dimensions as several other people including Stevant above so I can keep this fairly simple I think.

Expected payload about 200 Kilos max but some extra capacity would be nice just to be safe so let's shoot for 300 kilos.

Moment arm length 160mm but I'd also like to add holes like your arms for shorter and for longer moment arm length just in case I want to experiment. If this adds much cost we can just do the 160mm. As for the shorter and longer moment arm lengths I'm open to suggestions.

I'm happy to hear the shipping was reasonable!

Also a possible error in the dimensions I gave before: My ball joints have 5/8" holes. I said the holes the arms should be 5/8" but I'm actually not sure what hardware to use, whether to use a sleeve, etc. so I'm open to suggestions on that as well. Once the ball joints get here I'm planning to take one to the hardware store and check the fit on various hardware.

Thanks,
Trip

[Riton]

only 189 Nm 1000W!?
it not seem like much for a couple 1000W motor ...

I'll have it for 1100 W:
Motoréducteur coaxial
Moteur triphasé 230/400V. 1,1 kw. 1500 tr/mn. Taille 80
Rapport de réduction : 1/47,39
Vitesse de sortie : 30 tr/mn
Couple de sortie : 330 Nm
Poids : 30 kg

I have a rotating arm 24 cm

there is not a problem?

[DoctorD]

Heya Riton
The 189Nm limitation is purely from the gearbox manufacturer (probably more to do with the output shaft bearing or frame strength of the gearbox).
The motor itself will surely be able to produce plenty of power, it's just how much force it is limited to at the gearbox side is the question.
To give an example, the motor will be able to move a smaller payload very fast (because of it's large power) but it will be limited to the total amount of stress/torque that it can take at the gearhead/output shaft.
Be mindful, the gearbox may be strong enough to take much more than this. It will come down to how much of a factor of safety that the gearbox manufacturer has placed on their design sheets. It may be that the gearbox can take a bigger load, but that some part of the mechanism will break or wear out quicker if it is subjected to a higher than rated load.

As described above (for Stevant1) the maximum payload will be influenced heavily by your platform geometry. If the load stays relatively even over each gearbox, then the maximum torque at each gearbox will stay very low (comparatively).

I hope this helps,
DoctorD

[Riton]

ok, thanks,
no I think I know why there is this difference. the performance of these gear is less than the axial gear ... around 70% of memory then an axial reducer like me , is located near 95%.
a second point, I had this problem, the performance can be in continuous operation and allow a couple larger tip. That said it is necessary to consider the nominal value, or change for a gear to really spend the torque. that's what I do on my simulator.