ANH Motorised stunt Saber experiments (& blades) Part 1

[Mouse Vader]

That might be why Obi1 and Vader ended up with vastly different blade lengths, in order to experiment and reduce wobble

I agree & it's looking increasingly like the situation on set was much more complex than has previously been thought. From
Halliwax's weird V3 theory
pg10 post #196 the same Jon says there were app. 8 motorised sabers + some statics.

Looks like my idea that they didn't use gears is in trouble - which is a good (as that was my original instinct & choice) & bad (as I've just ordered a couple of gearless motors).

Here's my original schematic before I started work. (using the Oilite bronze bearing 3/4" / 19mm id )

The drive shaft bit in pencil was going to be a 19mm tube (15mm id) with insert at the motor end socketed to fit the motor drive shaft. The idea was for use with the balsa blades so they could be pushed in 'whole' & a friction fit so no need to drill a hole in the base or fit a stud. Having read the above I think I'll make one or something similar.

Thanks for the support so far, everyone. I too am keen see results but I have limited time to do this in so we'll all have to be patient. It will get done though, I've bought too many of the bits to give up now.

 

[vadermania]

Here is the sketch that Jon sent me yesterday.

 

[kurtyboy]

Here is the sketch that Jon sent me yesterday.

 

[Mouse Vader]

Here is the sketch that Jon sent me yesterday.

That's scarily close to my MK1a set up, right down to the paper shim !

Proposed MK2 as I outline in post #8 above is even closer as it will have the ballrace bearing.

Made the MK2 core today, fitted the bearing & motor. Just need to do a driveshaft & access holes. Hope to do that Sunday.

 

[Mouse Vader]

Did a couple of RPM checks a couple of days ago & forgot to post.
Counting frames MK1b is currently giving app 390 at 6.04 Volts, which is about 6.5 rps.
If I twirl it against the direction of rotation (In this case clockwise) I loose about 15 rpm but if I twirl with the the direction of rotation it stays the same.
(I hear a collective yawn.)

So some considerations on observed RPM:

YouTube or any MP4 video is a smidge under 30 frames / sec (fps) so smidgy I ignore it.
Cine film is 24 fps.
So some jiggery pokery goes on when cine film is shown on Ytube. I don't know how it works but there seems to be more than one method. I most often encounter a freeze frame, that is every 5th frame is a repeat of the 4th so this actually slows down the film action but not so you'd notice.
It makes frame counting blade rpm tricky.

From looking frame by frame at Ytube BTS footage I was getting 1 turn / 4 frames = 6 rps = 360 rpm as a figure for the cine film (24 fps) but if you apply the same 1 turn in 4 frames to MP4 (30 fps) you get 7.5 rps = 450 rpm. Hence my choice of a 400 rpm motor/gear set up as closest fit. Up the volts a little for 450rpm drop them a little for 360 & then see which looks closest to the original footage when on video.
The blade flicker is caused, mostly, by the black stripe coming in or exitting view on the blade edge, & is every 2 frames at 1 turn / 4 frames.

However while checking on 4k77 clips (looking to confirm the switch position on the graffy SFX) I noticed there were no freeze frames & I was seeing individual cells on frame advance. How they did this I've even less idea.
Using this as a source I was able ascertain a different rpm for the film footage which is 2 turns in 5 frames.
This gives a staggered (odd) number of frames between the black stripe hitting the edge.
Crunching the numbers this makes 10rps & 600rpm for (24fps) film and 12 rps & 720 rpm for (30fps) MP4.
Hence the ordering of some new gear/motors. 600rpm is not an easy one to find & I may have to up the volts on a 400 to near 9V. When I got them I tried them on 2 x lipo's in series (app 8.4v) & they were fine but I don't know what long term effect, if any. this might have. I've 900rpm too so that will certainly work on reduced volts but won't be so torquey.

This is the sort stuff that goes on in prototyping - fun isn't it?

 

[Mouse Vader]

Is this a jack plug I see before me? (& socket in hilt base?)

Ref Jon's sketch in post #22

If it is , is it on the saber or up Vader's sleeve? (I think the latter).

 

[Mouse Vader]

Got MK2 drive shaft done Sunday. RPM test using the the motor & battery pack from MK1b. Single ball-race bearing at the front. RPM is down by about 12 in the vertical, I'm not sure why, no loss at all horizontally - same 390 as MK1b. Unaffected in the swing so looks like a viable option. I'm surprised how well this worked.

In this test I moved the motor forward by about 2.5" to see if increase leverage out weighed reducing shaft deflection at the motor.

The answer is yes. RPM in the vertical was the same at about 378 but dropped in the horizontal to about 365 showing there was increased stress on the gearbox bearings.

Next up will be 1 or 2 one piece shafts for the MK1b to see if I can reduce play & get it to work on just the front bearing; put reflective fabric on the golf stick; make a new battry pack as the current one still has a duff joint I can't find & then figure out if I need to do a MK3 with dual ball bearings.
Doddle.

 

[kurtyboy]

I always thought that connector was hanging off the saber coming out of the lower hole like on Luke's.

I encoded my 4K clips at 24FPS so maybe YouTube preserves the frame rate?

 

[Mouse Vader]

I always thought that connctor was hanging off the saber coming out of the lower hole like on Luke's.

So hard to tell with just photo's - I'd have thought like you had it not been for Jon's sketch with a jack plug going into the saber pommel. If I get time I'll look at some footage & see if I can see any more.

I encoded my 4K clips at 24FPS so maybe YouTube preserves the frame rate?

That probably explains it, I'll try & check if it is still so. Proved useful in this case.

Today I made a new drive shaft for the MK1b giving just a single bearing at the front & also taking a good chunk of slop out at the same time. Looks like it may work but I need to paper shim another motor thick enough for that core... & for some reason the 5/16 socket I reamed (in the same way as all the others) was fractionally smaller & has grabbed the blade stud & won't let go so I now have a long stud drive shaft & socketed blade. I'll sort it once I've tried it out.

 

[Mouse Vader]

KB - can't find any info on the frame rate on your video's as on YouTube. I didn't know it could be changed on MP4 - my info came from a web search to find MP4 frame rate & this tallied with the info on my digiSLR.
Is there any way I can find out what frame rate a particular YouTube video is running?
I defo was encountering a repeat frame 4 to 5 on several of the BTS StarWars video's as other moving objects in the same view also remained static.

 

[kurtyboy]

Download the video (you might need a plug-in/extension for your browser) then look at the file properties.

 

[Mouse Vader]

I tried that too - no luck. Maybe not showing on Linux?

 

[Mouse Vader]

Here's the latest update. Have tested the new single front bearing drive shaft in the MK1b core, using a new 400rpm geared motor running on 8.3V as an rpm test. (480 so not a linear relation of volts to rpm.) Had to use card & paper shim on the gearbox to fit the rear bored out section. Prepped the 900 rpm motor too they just need tails now. (spare 400 top right.)

New shaft is the second from the top & runs nicely, I managed to remove a massive 1.5 thou (mil) in play - wow, gosh. no way.

I will be doing a MK3 now which is as MK2 but with single roller bearing of diferent sort than in MK1b. (no inner sleeve) & new 600 rpm motor (same style gearbox as above but longer motor).

Quick vid. MK1b single bearing.

Compare the sound with this clip, I'm doing about 480 rpm and am a little slower but apart from that - well you tell me?
[edit ; I've rechecked this on frame count & am actually about 514 rpm.]

The ANH LightSaber Blade Reference Thread

WELCOME TO THE ANH LIGHTSABER BLADE REFERENCE THREAD (aka ANH LSRF ) PLEASE – this is a reference thread. IF you want to comment, discuss – anything – then Please use this companion thread: ANH lightsaber blade Reference companion thread. ANH lightsaber blade Reference companion thread I came...

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VC4

 

[kurtyboy]

Scarily close.... just needs up a notch.

Glad you're doing all the leg work!

 

[Dann]

Dang, dude!

Some serious work you've got goin' on, here.

Keep it up, I wanna build myself a setup like this, so I appreciate all the documentation and time and effort you're putting into this!

 

[Mouse Vader]

Thanks Dann.
It's sort of turning into my experimental note book rather than a 'tutorial'. I thought I might show the sort of effort that goes into this sort of thing as it happens rather than a finished here's how you do it.

Also, for me, ideas often spring from other peoples dead ends or evolutions so this may help out others too.
There's more than one way to skin a rabbit as the saying goes.

Jon's info has already caused me go in new directions but I've not time just now to write it up - I will later.

 

[Dann]

Where are ya getting your motors from, if you don't mind my asking?

I wonder if I have anything here around the house that I could use. Hmm..

 

[vadermania]

Compare the sound with this clip, I'm doing about 480 rpm and am a little slower but apart from that - well you tell me?

The ANH LightSaber Blade Reference Thread

WELCOME TO THE ANH LIGHTSABER BLADE REFERENCE THREAD (aka ANH LSRF ) PLEASE – this is a reference thread. IF you want to comment, discuss – anything – then Please use this companion thread: ANH lightsaber blade Reference companion thread. ANH lightsaber blade Reference companion thread I came...

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VC4

In the last clip with Hamill, that's not a round stunt blade, what do you think?

 

[Dann]

Doesn't look round to me, at least the extreme contrast of the scotchlite vs the non-scotchlite as it's spinning makes me think square blade.

But it could all be an illusion, I certainly don't know.

 

[Mouse Vader]

Where are ya getting your motors from, if you don't mind my asking?

Fleabay. both the 900 & 400 are from this listing.

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I doubt I can get the 400 up as far as 600rpm, I'll give it a go but have other stuff to sort out 1st. I have yet to properly try the 900 in a core. Both the 400 & 900 appear to share the same motor unit which I have calculated to be running about 3800rpm on 6V. The 400 gear box is 9.68:1 (actually gives about 390rpm) the 900 is 4.4:1 (about 865rpm). I'll take one apart so you can see the gear train when I have time.

I have this 646rpm on order.

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It looks like it has a similar gear box but longer 30mm motor.

Gear boxes are 25mm diam x 20mm long which is a perfect match for that described by Jon. Motors are 24mm diam & 20mm long so much shorter than the 50mm (oal 70mm) he gives. He also gives a possible gear ratio of 20:1 which for a output of 600rpm gives a motor speed of 12000 which is well within bounds of electric motors.

I would caution holding off buying stuff until I've tried all the options I have & have yet to arrive.

In the last clip with Hamill, that's not a round stunt blade, what do you think?

I can't tell from this footage. Some of the hut scene photo's look to have a round blade with a black stripe wider than we see later on so this maybe what's going on...

which brings us to the whole point of what I'm doing here. Making motorised hilts that spins at the same speed, make the blades, spin them & see what we get. It's the only way we've got to answer these questions & even then we may not get answers.

My other reason for doing this is that this graffy SFX is the 1st on screen working lightsaber, & (as thd9791 points out in one of his threads) is actually the saber we all have taken to our hearts watching the film.

I've had a busy day. Saber stuff & some more observations on what Jon has told us for me to write. I'll try to do tomorrow.

Edit: Promised photo of gearbox internals.