Technical Review: PH1400 Multi-Tool SPLINE DRIVE (non-compatible with universal attachments)

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  • Updated 9 months ago

Summary: Ego uses a proprietary spline shaft drive system, therefore, non-compatible with existing universal trimmer attachments

Purpose: Illustrate the technical differences between the Ego spline drive and the universal trimmer attachment square drive

Idea: Ego should produce an adapter which allows universal trimmer attachments to be used on the Multi-Tool Power Head (PH1400)

Why: People have garages and tool sheds full of the universal trimmer attachments THEY need for their specific home/yard.  An adapter would allow consumers to get into the electric outdoor power equipment (OPE) market with a smaller initial investment.  A secondary benefit is that Ego has time to design/build/market "improved" version of the existing universal attachments.

History:
Universal Trimmer Attachments seem to have been around forever, and according to the US Patent Office, an approximate date would be 2004 or 2008 (reference 1).  Exact date is not important, the point is that these universal attachments have been around for a long time; and a lot of people have a large useful collection of the tools they need for their home/yard situation.

Technical Details:
Similarities:
S1) drive direction: spins CCW (counter-clockwise) when you look from the attachment end, into the power head. Additional details in Reference 2.

S2) quick release (button), secured by a clamp

Differences:
D1) drive method
Ego: spline drive, 7 flute, 0.270" O.D. (6.85mm ?#!); solid steel shaft 0.280" O.D. (7.11mm)
Univ: square drive, 0.200" (flat side), 0.282" O.D.; flexible twisted cable drive
Note: spline drive could handle more torque, but who's heard of a square drive getting sheared; but the twisted cables have broken.

D2) tube diameter &  material
Ego: 0.985" (25.02mm), aluminum tubing
Univ: 1.000" (25.4mm), steel tubing
Note: precludes putting a Univ shaft into a the Ego clamp without modification; weight difference likely negligible

D3) bearing method
Ego: sealed bearing, 6900RS (10mm x 22mm x 6mm)
Univ: flexible shaft, riding in nylon tube, supported by rubber inserts
Note: the sealed bearings are lower maintenance and more efficient, but cost more to produce

D4) clamping details
Ego: 3.125" (~80mm) clamp interface length
Univ: 1.75" (~45mm) clamp interface length
Note: Ego has almost double the clamp length, which will help with rigidity of extended pole saw operations

References and Links:
(1) https://www.google.com/patents/US20080141541?dq=Universal+Trimmer+Attachments+string+yard+tool&h...

(2) https://community.egopowerplus.com/ego/topics/multi-tool-power-head-which-direction-will-the-shaft-r...


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(a)Typical Engineer

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Posted 2 years ago

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Jacob

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Nice breakdown man. Awesome read.
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Blue Angel, Champion

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Great detailed look at the system!

Looks like Ego's system is technically superior in just about every way, except perhaps the aluminum tubing if ultimate ruggedness was a requirement.  It still would be nice to see an adapter to drive the universal tools.
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Phase 1: Fabricate an adapter; this is the simple prototype made from 3/4" PVC pipe, 5.0" long, the Ego end needed to be turned down to 0.985", and the Universal Attachment side is 1.00" (stock pipe was 1.050".  Don't get too excited because that was the easy step.  Also need to cut the square hole for the Quick Release (QR) on the Ego end.  Need to determine if Schedule 40 PVC is sufficient, or if Schedule 80 is required (for additional stiffness; 0.824 - 0.742 = 0.082 [0.041 wall thickness difference).  Or maybe CPVC, which I think is stronger still?

Phase 2: Figure out how to connect the two different drive systems.  My first attempt will be using 3/8-16 Nylon 6/6 threaded fasteners, connected in the middle with a coupler.  The Ego side needs to be a male spline drive, and the Universal side needs to be a female square drive.  I chose Nylon so that I can drill and get the sizes close, then I'm going to heat it (~500F melting point), and see if I can't get the nylon to mold to the correct spline/square shapes.  Next progress update likely next weekend.

Any insights welcomed!




(Edited)
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Blue Angel, Champion

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That's a universal spline for fasteners, and I think it's even-count as well. Probably wouldn't work with a 7 spline shaft:
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That was a good idea but wouldn't work.  I also looked at the Universal Socket, which also looked promising, but wouldn't be a good longer term solution (for the square drive female).

https://smile.amazon.com/BLENDX-Ratchet-Universal-Sockets-Adapter/dp/B01EC97Q7E/ref=sr_1_3?ie=UTF8&a...

The best solution for the square drive female side will be a solid piece of metal.  The proprietary Ego splined shaft might work in a non-ferrous material like nylon 6/6, aluminum or brass/bronze (which should be easier to work than steel).

Note: For the adapter, one side needs to be square drive FEMALE, and the other side Ego splined MALE.

(Edited)
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Jacob

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I should have told you this a while ago. Take the clutch square drive piece out of a trimmer, cut the head off of it and use that. It goes from 7/16ish id to square drive. Spline into that piece

https://www.amazon.com/dp/B00Y0O6XUI/...
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(a)Typical Engineer

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Hold out... I cannot believe it?!# =)  Actually, I can't believe that I just saw this... must have been buried in the +2000 Ego emails. =P
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I decided to sacrifice the Troybilt clutch rather than try and do the nylon bolt for the square drive (after a failed attempt last weekend).  In the first picture, the clutch bell and all important shaft drive is held to the flywheel by a bolt, which apparently #8-32.  Second picture shows the small end of the clutch bell fitting inside the PVC adapter tube.  Last picture shows a 5/16" nylon bolt dropped into the other end of the clutch bell; but I might go up to 3/8" and then shave it down to an exact fit since this is the end that will need the #8-32 screw to hold it in.

So the next part is to cut a 7-spline mock up into either a nylon bolt which may not withstand the shear torque forces, or more likely a brass bolt.  So that's the preview of the weekend project.





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This really is a wonderful review! Keep in mind that we are passing your ideas along to our development team.
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(a)Typical Engineer

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Should I send in my resume too? =)
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Amber F., Official EGO Rep

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Plenty of great positions available! http://www.chervongroup.com/en/careers
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Blue Angel, Champion

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There you go, a couple of product development positions in IL.
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(a)Typical Engineer

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Looks like I'm 2 years late to this party... Jacob already did something with a 12" trimmer; and he blew up the METAL coupler, so I think I'm skipping the nylon bolt option, and jumping straight to a metal rod.

https://community.egopowerplus.com/ego/topics/my-homemade-attachment-capable-model
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nigeldh

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Thanks for all the work to MacGyver a solution.
One can get Pole Saw Extension Pole, at Sears Part #: 622892-00. This gives you the "trimmer plus" connection. I wonder if 3-D printing is strong enough for the inner shaft - square on one end, splined on the other? I have sheared the drive shaft on one pole pruner head - so strength of the square connector doesn't seem to the issue folks think it might be. Shaft sheared, the square part didn't round the mating end.
Side notes: I can even use the "trimmer plus" with a Stihl Kombi.
For snow clearing I have several of the discontinued snow paddles from Ryobi. With an eGo winter starting should be less of an issue - why one of our power heads has the external electric starter unit.
(Edited)
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Here is the coupler Jacob blew up, it was metal...

(Edited)
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Summary: Drive Ratio for attachments, 12.5% difference

Background: One of them pesky Champions made a comment about ratios, so here's the investigation and report.

Test Units: 1) Ego PH1400/STA1500, and 2) Kobalt 80v Trimmer

Measurement Method: spin the shaft and count the trimmer head rotations (duh!), but I did sping the head and count the shaft to double check.

Discussion:
1) The Ego drive ratio is: 1.19 to 1, so if you spin the motor at 1000 rpm, it will 840 rpm; or if you spin the motor at 5000 rpm, the trimmer head spins at 4200 rpm.
2) The Kobalt drive ratio is: 1.36 to 1, so if you spin it the motor at 5000 rpm, the trimmer 3700 rpm.
3) Comparing the trimmers, the Kobalt spins 12.5% (1.19 / 1.36) slower, which means it has 12.5% more ratio advantage.  If driving a heavy torque application like the chain saw pole attachment.. . well you'd have to measure those ratios and compare, so there is a difference, but more data is needed for a true conclusion.

Assumptions: None.

Conclusion: The Ego drive ratio is close enough to the Universal Trimmer attachment ratio (12.5% difference) that an adapter to fit Universal Trimmer Attachments to the Ego PH1400 should be within the operational speed range of both the attachment and the PH1400.


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Darn pesky Champions... who do they think they are, anyway?
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Eric

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I'm not a champion, but you're welcome none the less.  

Is that at high speed or low speed on the switch?  In theory, I agree that 12.5% won't be an issue... however...

Note: The rest of this is based on my experience with the 12" trimmer. With my 12" there would be a spot where, under load, the motor would throttle down (assume for safety) and then speed back up.  This would be pretty common when cutting heavy weeds, trying to use it as an edger, etc.  The point is, I don't know what percentage of speed or bogging down by heavy work would cause this slow down of the motor.  Is it 5%?  12.5%?  30%?  Not sure.

Also, I'm not sure which attachments you want to use, but my #1 priority personally would be a small tiller attachment.  I'm keeping a close eye on this for that, and of course peeking my engineering interest.  I think some of these heavier load tools, would also compound the possibility of major motor throttling.

So point is, my 12" had this issue, but 12.5% and heavy tools may end up being a bigger deal than expected.  That being said, I have yet to get this new modular model to bog down at all.  I chopped right through 1/2" thick weeds (even without upgraded string / cord) that my 12" would never have been able to do.

Just something to think about.
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Speed: I'm waiting for Ego to post the speeds of the PH1400 power head, the reference to 5000 rpm was theoretical.

Throttling: I have not noticed the PH1400/STA1500 throttle down at all.  Nor have I noticed that on the ST1500 (w/ RR head, or bump head).  I've only used the PH1400 less than five times, but each time was cutting heavy brush and vines.  A few times a large vine (1/2-3/4" and you can hang 150 lbs from, so very strong) gets wrapped up and it stops, but that would stop any trimmer (gas/electric).

Torque: I don't have the tiller, but watching YouTube videos they seem to turn at a much lower tiller head speed, thus they likely have reduction built in.  Also when comparing gas vs. electric, gas has HP (horsepower) advantage, and electric has torque; so where a gas trimmer with tiller might bog down (or have to be spun up to max RPM), the electric should just churn away.

Ramp-Up: I don't have the Ego chainsaw but my Kobalt 80v CS has a very specific ramp up curve; it will start cutting at medium speed and once it senses a higher load (like you are really laying into a log), it will jump to high speed until you let off the throttle, err... switch.  My 20" mower will do something similar, but only when I hit a thick patch of grass, very much like the turbo button on the blowers; it "boosts" for a second or two, then rpm drops back to normal.

Tiller Reduction: A brief search on tillers, reveals the standard seems to be a 42:1 reduction; so the motor spinning at 5000 rpm would drive the tiller head at 120 rpm, which is pretty S-LLLLlllll-OOoooo-www.
http://www.homedepot.com/p/ECHO-6-1-2-in-Tiller-and-Cultivator-Attachment-99944200513/202042631
(Edited)
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Jacob

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My 20" also does that, but only if the 5 ah battery is being used.
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Alright, PROTOTYPE completed, here are the videos (technical details in a follow-up post).











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Still pictures with universal attachments.






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Build Pictures:





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Installation Pictures/Steps:




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Summary:
PROTOTYPE adapter successfully connected universal trimmer attachments to the PH1400 Power Head

Challenges:
Cutting the splines.  I set out to use nylon 6/6 bolts, but oddly those were more difficult to turn down to the initial diameter than soft metal (brass).  so after spending 30 minutes with little success, I switch over to BRASS bolts.

Design Choices:
I decided to use a 5/16" threaded rod as the primary shaft material.  A 5/16-18 coupler was used so that different spine shaft material could be tried (which worked out really well after the nylon 6/6 issues.

Build Issues:
Cutting splines by had was a real fun task.  As such, the shaft is not completely centered, and when it starts to spin at low speed, it wobbles (see video below); however, once up to maximum speed (#2, high), it is complete vibration free.  You'll notice in the video that right after spinning up, and right before stopping, the adapter will wobble.  I will add a sealed bearing to the universal female square drive end, since the Ego already has a sealed bearing right behind the female spline drive (actually that is an assumption based on the 31" pole extension design). If the wobble is left unchecked, the female square drive adapter was rubbing on PVC pipe internal (starting to cut a groove, last picture).

Operational Observations:
With the brush cutter, that head has a lot of rotational inertia; and when you first spin it up, it torques noticeably.  The work around is to spin up the motor slowly, which is very easy to do with the variable speed trigger.

Build COST:
Universal trimmer clutch, which is used for the female square drive, $20
brass bolts, 5/16-18 x 3-1/2", $3
coupler nuts, 5/16-18 x 7/8", $3
PVC tube (or aluminum), 1" OD x 6", $2
rod, threaded, 5/16-18 x 3" (1 ft min), $4
nuts, self-locking, 5/16-18, $2
universal trimmer coupler, $20 (estimate)

Build cost discussion:
The most expensive part is the universal coupler for $20.  And the next most expensive part is the female square drive coupler, which would have been easier to fabricate from a 1/2" steel bar stock, than hand cutting the splines in the brass rod.  Parts for a production unit would probably be around $35.  So an adapter could easily be made/offered for $50-75.

Next PROTOTYPE changes:
1) add a bearing to support the adapter
2) switch the PVC tube to metal (likely aluminum)

Future Testing:
My only concern with the design is whether the brass splines will stand up to a hard impact when using the brush cutter, so that is on my list of things to test once I get the sealed bearing support added.  Should that fail, the solution would be to change from brass to steel, as that is the same material Ego is using for their production version; however, I do not anticipate that the brass spline drive will fail.


Ego Team, Suggestion:
As this prototype demonstrates, universal attachments appear to be very usable for use on the PH1400 power head.  Please consider having your Engineering Team evaluate the technical feasibility, as well as the Marketing Team determine whether there is a market case which supports development.





(Edited)
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Temporary fix (because the hardware store didn't have any sealed bearings) was to install a 1/8" thick nylon washer, cut down to the inside diameter of PVC tube; now when the motor starts up, the adapter is centered, and once it picks up speed it keeps it centered.  Put a dab of grease on there for good measure.

Stuck the brush cutter on there, and it whirls away nice and smooth.  With a proper sealed bearing, this thing is going to be really smooth.

(Edited)
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After further testing, this was a band-aid fix that did not address the root cause, which was the wobble (see the video above).  I'll discuss the analysis and the fix in a new thread below (to keep everything relatively in order).
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Eric Beadle

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You're onto something here!!! This is something that all companies could take charge of. The only dilemma I see is not having enough power for some of the stuff like the Stihl KombiSystem. 
(My favorite gas tool for the amount of items you can attach to it. )
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(a)Typical Engineer

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I see that the Stihl website says for use with Stihl only; is that true, or just the typical corporate disclaimer?  It does appear to be a modified square drive.
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nigeldh

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I have used a Stihl Kombi drive head with Trimmer Plus like the pole saw, brush cutter. This fact was in the listing for the first Kombi power head I got on eBay, the reason I got it. I haven't gone the other way - my Kombi trimmer head with my Ryobi, TroyBuilt 4 cycle power head.
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Summary:
Brush Cutter Test Satisfactory! (with minor adapter issue)

Background:
On the hills in my backyard, there is an undesirable plant that has large leaves and thick stalks.  No string trimmer will effectively cut it (I tried for a couple of years with gas too); the trimmer string just wraps around the stalk, gets tangled and stops.  I bought the brush cutter specifically for clearing these plants.

Test Setup & Attachment Details:
Ryobi RYBRC77, 8 in. reversible heavy-duty steel TRI-ARC blade. [1]
Battery: 2.0 AH and 2.5 AH

Operational Observations:
Within the first few minutes, I hit a soft log and it stopped the blade instantly, and also twisted the attachment body at the connection point (see pic below, 90 degrees out). Which wasn't a problem as I loosed the connection point, rotated it back into position, and continued on.  And in a way, that is better than having something shear off (like the spline drive!).

One other thing I did try and test was the variable speed of the PH1400.  In order to save battery life, I usually don't run it full throttle unless I'm going after a thick cluster of stalks.  The speed modulation was pretty good.  Just like my Kobalt 80v attachment capable trimmer, the Ego does take a second or two to get to full speed, but once you're at speed, it will hold it there without issue.  Overall, I'm very happy with the way the Ego modulates the speed of the motor.



Test Details:
For this test, I cut an area about 20' x 30' (600 sq. ft), and these plants are spaced every 12"-18".  The plants in the foreground are about 12" high, and that was a few months of growth; the uncut plants in the top half of the picture are about 3-4' high.  These plants have a root bulb that sits just below the surface, and if you can cut down into that, the regrowth takes longer, which is what makes the brush cutter attachment so effective and controlling this plant.  And since you're cutting so close to the ground, rock strikes are very common.



Issue:
As the height and density of the plants got higher and heavier, the brush cutters started to get tangled up more.  At one point, I snagged a 1/2" vine and it wrapped the blade and completely stopped the cutter.  Most times I can power through the snag, and I tried this time, but the motor spun without the head moving; which made me think for a split second that Ego added a slipper safety clutch.  But upon disassembling the adapter to check, I found that the spline drive adapter that I epoxied to the hex nut had broken the epoxy, and that joint was spinning freely (first picture below).  I also inspected the brass spline of the adapter and was pleasantly surprised that the splines were holding up nicely; so at least in the short term, the brass is sufficiently strong (the red color is chicken blood made as an offering to the engineering gods). =)





Solution:
My first idea was to hammer the adapter into a hexagon shape, but after the first hammer blow it was apparent that this was a hardened piece; and with the second blow the body developed some hairline cracks.  At that point I moved to plan "B" which was to just hammer it enough so that the hex nut would not spin freely.  I secured the hex nut with epoxy (same as last time).  I performed an initial test of just running it under no-load in the garage and it works again as before.



Discussion:
The brush cutter head should be the most challenging attachment in terms of torque as well as impact tests.  While the tiller would be a more continuous torque load, it also has a 72:1 gear reduction, so it has a huge mechanical advantage.

Follow-On Test:
I'm going to use the chainsaw attachment this weekend on a tree pruning project, report to follow.  I think this will work without issue due to the low load and low speed.

Conclusion:
The 2000W motor of the PH1400 has sufficient power to drive a brush cutter attachment.  I cannot wait until Ego releases the brush cutter blade for use on the STA1500 for the US market!

References:
[1] Ryobi Brush Cutter on Home Depot:
http://www.homedepot.com/p/Ryobi-Expand-It-8-in-Brush-Cutter-Trimmer-Attachment-RYBRC77/100313611
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nigeldh

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I wonder how the Rino-Tuff blades would work - they are swing-away blades just like in a heavy duty brush mower. I use the Rino-Tuff Brush Cutter Replacement Blades - metal core, plastic wrapper. Both in my trimmers and also in my DR trimmer mower. I had to drill the hole a bit bigger but they last hours even when trimming woody shrubs.
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Scott Blanchard

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The Grass Gator "Extra Heavy Duty" brushcutter head is similar but all metal blades. Mine has lasted 3 years with heavy abuse! Best $15 I've spent in a while:



Trimmer is a CORE power 36volt (now discontinued and sold to Troy-Bilt/Cub Cadet). Its a beast of a trimmer, has two speeds (5k and 7K rotation) but I'd expect the EGO powerhead's 2KW motor is even more powerful.
(Edited)
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Pole Saw attachment, both Universal and Ego (EP7500) extensions

Equipment in this post:
PH1400 power head
EP7500 31" extension
Troy-Bilt ~2-1/2' extension
Troy-Bilt Chainsaw attachment

First setup is 8-1/2 feet, second one is 11 feet.  Of course the really long setup is only useful in a nearly vertical usage, as the poles tend to sag quite a bit.

NOTE: Ego's official position is that only a single EP7500 31" extension should be used, no more!







(Edited)
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Okay, admittedly that 11-1/2 foot setup is a little dumb, and I did post previously "Just because you can, doesn't mean you should".
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nigeldh

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Or for clearing snow off the roof with the old snow paddle attachment. grin
Now for the YouTube epic fails videos. wink
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Build: v1.1, wobble fixed, bushing implemented, unit is now self contained

Summary
: Simple bushing and alignment issue resolved

Find the wobble source
After thinking about it more, I disassembled the adapter and put only the brass rod spline in the PH1400, and when spinning it had about 1/16" of run-out, so I bent it to minimize the run-out.

Compounded Error /!\
Then I added the 5/16" coupler back, as well as the steel connector rod, and the final female square drive adapter.  The run out caused by the coupler was pretty significant.  I was assembling it by butting both the brass threaded rod and the steel threaded rods together.  However, after thinking about it, unless those faces are absolutely flat and sit flush, that could cause the rods to be out of concentricity, and would therefore introduce a wobble at the female square drive end.  The wobble would be on the female drive side because the brass spline end is supported by a bearing right next to the female Ego spline drive.

Simple Fix
The fix was very simple, when making up the coupler joint, I left a small gap between the two rod faces and that was enough to have nearly zero run-out.  Which left the issue of supporting the spinning rod.  Going back to my temporary fix of adding a nylon washer was a non-starter.  I demonstrated this for myself by spinning the adapter and accidentally touching the nylon washer, which was spinning so fast that it gave me a friction burn from a split second of contact.  Between the wobble from the misaligned coupler, and the high speed spinning washer, it was no wonder the inside face of the PVC pipe was being chewed up.  It would have been only a matter of a few more runs before that cut completely through the PVC tube.

KISS (Keep It Slippery Stupid)
So off to the hardware store again, and this time I'm looking for a very specific sealed bearing, a 698Z, which is 8mm ID, 19mm OD, and 6mm WIDE.  I had low hopes of finding one, so I looked for alternatives.  If you look back at the original square drive, those flexible shafts are riding inside of a very long and smooth tube.  I found a "plastic socket" which is for mounting casters inside of metal tube (chair) legs.  The plastic is a very hard type which is perfect for this application.  In short, this is the perfect piece to keep the adapter spinning dead center.  Another reason this works well (and why the nylon washer does not) comes down to surface area.  The 5/16" diameter and 1" long "bearing surface" of the new plastic bushing is much larger than the 3/4" diameter by 1/8" wide nylon washer, by 675%. [1]

Extra Insurance
For good measure, I packed the bushing and threaded rod with white lithium grease.

Conclusion:
As I posted above, the nylon washer "temp fix" was a terrible idea.  That was a band aid fix (which wouldn't have worked long term) for the real problem which was a summation of many little misalignments, which compounded into a really bad wobble. The videos of the PH1400 under no load is very promising, especially when at "HI" speed.

Follow-Up Testing:
Going to put some run time on this setup and see how the bushing holds up.  If the threaded rod chews up the bushing too much, the next thing will probably be to jump to a sealed bearing solution.


Footnotes:
[1] comparison of bearing surfaces: 5/16" x 1" = (2*pi*r or pi*D, 1.99 in^2), vs. 3/4" x 1/8" = pi*D, 0.29 in^2).  The long bushing has 6.75 times more surface area (675%)!



(Edited)
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Tested the PH1400 with the build v1.1 adapter, and a Troy-Bilt TrimmerPlus PS720 pole saw.  This is the Ph1400 to adapter to PS720 (no EP7500 extension).  Here are two videos cutting some small branches (1-1/2 to 2").  Overall the adapter performed well.


(Edited)
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Ego Team, any update on whether Ego is producing an adapter to allow universal trimmer attachments to be used on the PH1400 power head?
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Jacob

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I'm pretty sure the spline was chose because the square is too weak for the power behind the power head. The gas ones have a minimum Rpm clutch in them.

All i got to say is if you make something like that proprietary. You better offer all of the attachments that are available.

This is not what is happening.. better get on it ego.
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(a)Typical Engineer

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Isn't the purpose of the clutch to allow the engine to keep idling and to be disconnected from the shaft, e.g. the attachment will not keep moving at idle?  An ON/OFF electric motor setup wouldn't require that, and can get away with a direct drive setup.

@Scott, absolutely.
(Edited)
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(a)Typical Engineer

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I'll re-post this from my original post:

Why: People have garages and tool sheds full of the universal trimmer attachments THEY need for their specific home/yard.  An adapter would allow consumers to get into the electric outdoor power equipment (OPE) market with a smaller initial investment.  A secondary benefit is that Ego has time to design/build/market "improved" version of the existing universal attachments.
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Jacob

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Yes. But I would imagine that it allows for some slippage. Kind of a fail safe to motor stalling. It's a metal on metal contact so maybe it won't allow for slippage. But still a huge issue in my opinion that they don't accept universal attachments. They could have offered a power head replacement to the whole market. Instead the got greedy. Well get on designing all the tools already out there ego.......... Better hire like 10 more engineers.
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(a)Typical Engineer

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Jacob, I would say any clutch slippage would be the exception, not the norm.  Pretty sure the primary reason for the clutch is to "safely" allow the motor to be disconnected, the secondary benefit is that you don't stall the engine.  I would agree that having a way to disconnect the drive system in an overload condition would be a good thing, and there is a slight chance that a clutch could function in this way, but that would be a secondary benefit.

Yes, Ego could have (or still can) dominate the entire Universal Tool attachment market if they can get over the greed factor.  I've said it already above, but the two phase approach is to FIRST introduce an adapter, and then over time they can develop better replacements, and possible have market domination in 5-10 years.  But we're still stuck on the decision to "make an adapter".

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(a)Typical Engineer

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Compatibility Report: used two different attachments, Kobalt 80v 15" trimmer, and Ryobi curved shaft trimmer.  The bump head on the curved shaft is a little sensitive so it burns through string quickly, so I switched over to the KB for the majority of the work.  Went up the steep hill, and back down towards the porch.  These batteries were not fully charged, so I ran through a 2.0 and 2.5 in under 30 minutes, and I was being frugal with the power.

Discussion: No compatibility issues identified with either trimmer head.

Conclusion: Going up and down the steep hill, the 15" dedicated trimmer (ST1500) is a more appropriate tool for the job, in both weight and battery endurance (I can usually do the entire hill (Up/Down) on a single 2.5 AH.

 




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Blue Angel, Champion

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Of course I don't know for sure, but I suspect the Ego spline drive would be stronger and perhaps more efficient than the universal square drive. And the curved shaft accessories would DEFINITELY be less efficient.

The efficiency of the spline system could have to do with alignment as well; a straight shaft supported and located by bearings would surely align better, both in offset and angle. Their die cast aluminum couplers are very stiff looking as well.

With gas power tools nobody worried about efficiency... if you ran out of gas you'd just filler up and burn more. Gas is cheap in this half of the world, and the OPE market was developed and established in an era where nobody gave a crap about the environment. The two-stroke engine is proof of that.

I really hope Ego has a riding mower solution before my new lawn is established next year. I really don't want to buy any gas powered OPE.
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Chris Simmons

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I would love it if EGO would make an adapter or maybe the universal company make an adapter to fit EGO.  I already have all the multiple universal tool heads and hate to have to repurchase all over again through EGO!
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Jeremy Fernandez

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Industrial engineer and product manager here. I own the EGO chainsaw and love it. IMHO EGO built a great system, but the proprietary connection on the power head is a huge oversight at best, and a bad decision at worst. I bought the Hustler Zion several years ago and saw the same oversight. I replaced the batteries with aircraft grade lithium. Runs like a champ. To save 10% on sale price, hustler put lead acid batteries good for 60hours of battery lifetime instead of lithium which are on track to get me thousands of hours of battery lifetime. Hustler could have been the Tesla of lawn equipment and change the industry. Instead the line was shut down. I have built my own solar powered weed trimmer, and was part way to retrofitting my existing gas weed trimmer when EGO released their trimmer line. The only thing missing is backward compatibility. As evidenced by myself and the garage inventors here, eco minded folks don't want to throw away every lawn tool they have, just the gas guzzling part. I won't buy the EGO trimmer until it fits my incredibly useful existing tools. I'll visit back here often. Excellent engineering work by EGO and others here. In the meanwhile, there's enough work here on the adapter that you might consider speaking to a patent attorney. Let me know when I can buy the adapter, or stock in the company who does.
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Blue Angel, Champion

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I'd be surprised if the spline drive and bearing supported straight shaft design that Ego has implemented isn't quite a bit more efficient at transferring power than the square drive and flex shaft system used by most of the existing products.
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(a)Typical Engineer

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Sealed bearings and a solid shaft vs. nylon bushings and a flexible shaft will undoubtedly be more efficient.  However, if you think about where the power is being "spent", it's probably 90% to spin the motor/attachment, and 10% due to friction and torsion loss (or some combination of that).  The of the 10% non-drive loss, probably 80% of that would be friction; therefore in the grand scheme of things, 90% to drive the attachment, 8% (80% of 10%) for friction, and 2% due to torsion loss (or some combination there-of).
I did manage to twist the brass bolt I was using; and the square drive did not break, but I'll post an update about that later.
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ignisuti

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Are you interested in building another and selling it to me. If so, name your price.
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bwsr

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This reply was created from a merged topic originally titled Power head compatibility.

I know the EGO power head is not compatible with the "standard" square shaft used by several other brands.

It seems almost every brand uses that square shaft, but I think there are maybe a couple that don't. Does anyone know if any of those happen to fit with the EGO unit?

I'm thinking of Honda's gas powerhead specifically. I believe Chervon is making Honda's new European line of battery powered tools, right? So there's already some cross-licensing or sharing of products between these brands. Maybe their attachments would fit on the EGO? It looks like they use a splined shaft, but from what I've seen can't really tell if the number of splines or size matches.

I've also seen a brand called EcoPro that might have a splined shaft, anyone know anything about that?

I'd really prefer to buy Ego attachments since I've been impressed with their other tools so far, but with the availability issues, and attachments like the hedge trimmer that are not even offered yet, this could help fill some gaps.
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Joseph Hubacek

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(a)Typical Engineer OK Its been 2 months!  I need to see the next iteration!