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Graham T

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Member #: 1106
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Hungerford, Berks

On 11th Jul, 2019 Joe C said:
Im supprised its 85 turns of the lead screw to go from short to long.

To go from short to long would only take 12.5 turns

But to hit each of the blue figures in this table ( that I currently have as the lengths to aim for) as the Revs increase, means the extension through the rev range would not be straightforward short to long extension.

Rather the extensions would have to yo-yo in and out

Hence the overall distance traveled for the rev range 2250 6250RPM might be up to 680mm, so 85 rotations of the lead screw.

On 11th Jul, 2019 Joe C said:

somthing to watch out for, we have used steppers here at work, and ran into heat issues with them due to the over;ap timings on the steps, basically the stepper fighting itself. that wias with a generic stepper friver pcb. we had to do our own and fudge the code to stop it.

Yes, these are concerns and also why I have found I need to keep the RPM/ steps per second or whatever low.
Im also going to experiment with a couple of different driver boards.
Currently I have an A4988 that I am using, but I will also try a few others to see if that changes the motor characteristic / behaviour.

On 11th Jul, 2019 robert said:
could you gear the motor to the shaft then use multiple motors ?

The concerns I have Robert, is the weight firstly, secondly more complexity in making parts and thirdly the final size of the package.

This single 17HS4401 I currently have is 290g
The next NEMA 17 I mention above, which is 17HS24-2104S, weighs 500g and is 20mm Longer.
Once I go to the NEMA 23, we are then talking 750g, but that has 1.26Ncm holding torque and shows up to 900RPM on the torque curve

Im not concerned about overall weight of the car, if you saw the amount of steel in the darn thing to stiffen up where the roof was removed you would see this is not going to make much difference; rather the weight hanging off of the 1.2mm wall aluminum pipes. As it is I think I am going to brace top to bottom runners once I start fitting it.

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