Scorpion SII-4020-540KV Prop Shaft Threads - RC Groups
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Nov 09, 2017, 08:54 PM
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Scorpion SII-4020-540KV Prop Shaft Threads


Does anyone know what the prop shaft threads are that come with the Scorpion SII-4020-540KV motor? I assume they are metric and probably 6x1.0 to 8x1.0 mm, but need to be sure.

I've checked everywhere I can think of and can't find that info.

Thanks.
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Nov 10, 2017, 04:58 AM
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Fourdan's Avatar
Quote:
Originally Posted by Rc_heli_flier
Does anyone know what the prop shaft threads are that come with the Scorpion SII-4020-540KV motor? I assume they are metric and probably 6x1.0 to 8x1.0 mm, but need to be sure.

I've checked everywhere I can think of and can't find that info.

Thanks.
Hi
For SII 4020-xxx :
Internal shaft : 5.98mm (6mm)
Bolt on prop adapter : M8-125 (ISO normal pitch), 3x M3 on 18mm circle
Collet adapter : M8-100 (fine pitch)
Louis
Nov 10, 2017, 08:16 AM
Registered User
Thanks Louis, appreciate it!!
Nov 14, 2017, 12:56 PM
Registered User
Ok guys I just received my Scorpion 4020 motor and I'm trying to figure out how it should be assembled for use in a plane. I assume the silver collet adapter should be used for the prop. What application would the black adapter be used for? I briefly installed the motor on my plane and the front of the collet adapter would need to come out about 1/4" in order to clear the front of the cowl. Are the set screws on the motor shaft there so the shaft can be moved forward or back in the motor (forward is needed in my case) so you do not need to put standoffs behind the motor?
Trying to find any instruction on the internet has proved fruitless.
Thanks for any info!
Nov 14, 2017, 02:07 PM
Registered User
Ok, I see that the motor shaft really doesn't adjust back and forth. Here is a picture of what I have. I assume that either the silver collet adapter or the black adapter can be used for a plane to mount the prop. Is one better than the other ? The aluminum sleeve pictured was in the bag with the black adapter. Should it be slipped over the motor shaft before attaching the black adapter?
Nov 15, 2017, 08:33 AM
Jack
jackerbes's Avatar
The magnet housing will self center itself over the stator arms when the shaft and housing are put into the inner bearing races. That position is where the magnets and windings have their best interactions and the motor develops the most power.

And when it is in that position the shaft, if properly designed, will have the grub screw flats and Circlip grooves in the right locations to keep the shaft in that position (relative to the housing) and tranfer forces to the base plate and mount and vehicle.

If you find them in the wrong place or want to change them you can do that with a Dremel tool. These threads shows examples of doing that:

Replace/modify shaft:

Making-and-Replacing-a-Brushless-Motor-Shaft - https://www.rcgroups.com/forums/showthread.php?1240725

Fitting prop saver:

Prop-Savers-Fitting-Using-Testing-Making-Thera-Band-Bands - https://www.rcgroups.com/forums/showthread.php?1419378

Disassembly:

Outrunner-Disassembly-and-Stripping-Gimbal-Motor-Rewind - https://www.rcgroups.com/forums/showthread.php?1823636

Making/Modifying a replacment shaft:

Making-and-Replacing-a-Brushless-Motor-Shaft - https://www.rcgroups.com/forums/showthread.php?1240725

I think that small cylinder will fit into the bolt on prop adapter and match the stub shaft on the front of the motor to the hole in the prop adapter. So putting it there just further ensures that the adapter is concentric with the shaft. The Scorpion pages don't show that as an accessory that comes with the motor.

Jack
Nov 15, 2017, 08:58 AM
Registered User
Thanks Jack.

One question - which is better to use for a regular APC prop , the collet adapter or the bolt-on adapter? It looks like the collet adapter would bit into the prop better, but really wasn't sure what intended purpose the bolt-on one was for.

Leon
Nov 15, 2017, 07:04 PM
Jack
jackerbes's Avatar
Quote:
Originally Posted by Rc_heli_flier
Thanks Jack.

One question - which is better to use for a regular APC prop , the collet adapter or the bolt-on adapter? It looks like the collet adapter would bit into the prop better, but really wasn't sure what intended purpose the bolt-on one was for.

Leon
Either one will work as well as the other.

On the collet type I always degrease the shaft and the inside of the collet before I put it on. And I made sure there are no burrs or metal scraps on the in side or the collet fingers.

And on some shafts I will wrap a piece of 600 grit emery cloth around the shaft and run the motor for a few seconds before I degrease it to make sure there there no coatings on it and to leave very light striations that improve the grip of the collet on the shaft. When you fit the collet the first time put a prop on the prop shaft and then the prop washer and prop nut (loosely). As you tighten the prop nut it presses the hub back and closes the collet to grip the shaft. The prop let you get a better grip on the adapter.

I have had shafts that had such a highly polished finish on them they looked like they had a plating (nickle? chrome?) and those are the ones that really need to have the surface worked over with the 600 grit emery cloth. You are not changing the size of the shaft, only changing the surface condition a little to let the aluminum collet fingers get a better grip on the shaft.

When the collet starts gripping the shaft you only want to tighten it about 1/16th to 1/8th of a turn or so. Don't try to get it any tighter at first or you run the risk of stretching and even breaking the the prop shaft as it is only aluminum.

Then grip the housing with one hand and see if you can make the collet adapter slip on the shaft with only moderate force. It is does not slip you are OK, if it does tighten it a tiny bit but more but just until it does not.

When you change or replace a prop, the collet will not lose it's grip. To get the collet to release you need to back the prop nut off until it is about one turn above even with the prop shaft end to protect the end of the shaft, then let the plane hang vertical resting on your fingers or a large open end wrench so you are supporting the weight under the prop hub (on the back of piece that is against the prop when tightened).

Then give the prop nut a sharp blow with a nylon or plastic or wood hammer or even a piece of good scrap hardwood and the collet will release.

If you don't have anyone to help you and catch the plane when the collet loosens (it can slip out of the wrench or your hand) do it seated and with the wings so they can land on your legs to avoid damage to the plane.

For most purposes, the collet adapter will never come off until you want it off and take it off as I describe. It is possible that it can come off in a hard nose impact if the prop comes out of the hub but at that point you'll probably have extensive damage to the mounting or a bent shaft or other worse problem to worry about! :>)

I am a strong proponent of using prop savers because I fly at a rough field location and don't have a runway. I have to hand launch and so stall/flop landings into deeper weeds. And that works fine for me because of the prop savers. Details on that here:

Prop-Savers-Fitting-Using-Testing-Making-Thera-Band-Bands - https://www.rcgroups.com/forums/showthread.php?1419378

Jack
Nov 16, 2017, 07:08 PM
Registered User
Thanks Jack, very helpful. You would think Scorpion would provide some sort of info with their motors on the various ways the prop shafts can be attached. No info from them at all that I can find as to the thread size of the prop shafts either.
Nov 18, 2017, 01:05 AM
I am a nice guy! Really!
Thread dedicated to Scorpion motors. Much info on prop adapters. You have to wade through or do a search to find though.
Nov 18, 2017, 05:05 AM
Registered User
Quote:
Originally Posted by Fourdan
Hi
For SII 4020-xxx :
Internal shaft : 5.98mm (6mm)
Bolt on prop adapter : M8-125 (ISO normal pitch), 3x M3 on 18mm circle
Collet adapter : M8-100 (fine pitch)
Louis
Louis,
Just to let you know both of the prop adapters have 8x100 threads. I got mine this week and had ordered prop nuts with 8x125 threads based on what you had said, so just wanted to let you know what they are now shipping with the motors.
Nov 18, 2017, 05:53 AM
Registered User
Fourdan's Avatar
Quote:
Originally Posted by Rc_heli_flier
Louis,
Just to let you know both of the prop adapters have 8x100 threads. I got mine this week and had ordered prop nuts with 8x125 threads based on what you had said, so just wanted to let you know what they are now shipping with the motors.
Hi
My Scorpion SII 40xx-xxx samples are from june 2013
Louis
Nov 18, 2017, 07:23 AM
Registered User
Quote:
Originally Posted by Fourdan
Hi
My Scorpion SII 40xx-xxx samples are from june 2013
Louis
Thanks, I just wanted to let you know. Personally this wouldn't be an issue if Scorpion would supply this sort of info on their products.
Yesterday, 10:21 AM
AMA 754
BobRCnut's Avatar
They do, on Scorpion's own web site. Here's the link for your 4020. It shows basic specs, and at the bottom of the page, links to their prop data and to the exact dimensions sheet:
https://www.scorpionsystem.com/catal.../SII_4020-540/

There is no "best" prop adapter. Many manufacturers offer both bolt-on and collet-type adapters because different aircraft use different motor mounting methods and positions, e.g., motor in front of firewall, motor behind firewall with shaft through a hole, motor reversed end-to-end, etc. Not all motors include both prop adapters because not all motors have the shaft protruding from both ends.


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