Big mid-drive motor, bypass IGH?

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Big mid-drive motor, bypass IGH?

Post by john61ct » Apr 24 2020 4:16pm

Noob here especially about how drivetrains work so please be gentle

Would it be possible to set up a Lightning Rods Big Block with its left hand heavy chain driving the rear wheel

completely separately, from a **mechanical** POV, from the human-pedaling force driving a relatively weak IGH ?

Application is a heavy tandem / cargo with occasional very long climbs up steep mountain roads.

So I want that crazy high torque when needed, but reckon that would likely destroy the gearing hub.

So, ignorance showing, does this mean two freehubs?

or a freehub plus a freewheel or something?

Please don't argue against the IGH idea - for purpose of this thread anyway, assume a thought experiment to isolate out this one specific question.

I'm fine with a single **very** low gear for the motor, and if that means basically human power only on the flats, once past 15mph, that is also fine

but ideas for getting shifting, say maybe 3 gears would be welcome, if it doesn't complicate things too much?

Would also like strong regen for safe drag braking on long descents minimizing pad wear.

If none of this is sane just say so 8-D
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Re: Big mid-drive motor, bypass IGH?

Post by john61ct » Apr 25 2020 3:36am

Realized I may not have written clearly enough
john61ct wrote:completely separately **from a mechanical POV** from the human pedaling force driving a relatively weak IGH ?

Is this meaning two freehubs, or a freehub plus a freewheel or something?
that I want the lightning rod's left-hand #219 chain to drive the rear wheel at high torque / low wheel rpm say grinding slowly up a long steep slope

without going through the relatively weak IGH.

IOW that the IGH is only driven by lower-torque human power, for example on the flats at higher speeds, say 10mph and over.

.
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Re: Big mid-drive motor, bypass IGH?

Post by Drunkskunk » Apr 25 2020 4:16am

totally possible. Not all that hard, depending on the IGH. They make sprockets to fit on disk brake mounts for ebikes and ICE bikes conversions, so adding a left sprocket is simple enough. The only hard task will be in setting up a freewheel. You won't be able to add a freewheel to the left side wheel sprocket, so you'll need one at the motor or on a jackshaft in between.

Building a multi-speed left hand drive is the kind of thing you need access to a machine shop for. I'd do it with motorcycle transmission gears, but someone posted plans of an chain and sprocket transmission on here once. it's possible to make something like that, if you have time and the tools.
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Re: Big mid-drive motor, bypass IGH?

Post by john61ct » Apr 25 2020 4:31am

Well that's encouraging, hope you're right!

The Lightning Rod stuff I believe is supposed to come as a turnkey kit, but maybe just for certain frame types e.g Qulbix Raptor, have not gone down that rabbit hole too deep just yet.

https://www.electricbike.com/lightning-rods-big-block

I may even go for the newer higher power XL version which I believe the mounts etc are still under development.

https://m.facebook.com/613804531978401/ ... 1649163652

Maybe it already comes with a freewheel? I dunno.

Now that I think about it, that might eliminate my option to get any regen, never mind as powerful as I need.

At least that's what I infer from my recent learning about the GMAC, which is not as powerful as these LR options I believe.

But I don't know about any transmission options, you mean actual shifting right?

That might be nice I guess, but right now the plan is to only use the LR motor for low speeds, especially when very high torque is needed, so I'd be OK with fixie style (is that the right word for single-chain "one speed"? 8-D)



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Re: Big mid-drive motor, bypass IGH?

Post by john61ct » Apr 25 2020 4:39am


Drunkskunk wrote:totally possible. Not all that hard, depending on the IGH.
Right now thinking of Sturmey Archer 3- or 5- to start, whatever helps best with standing starts uphill with a heavy rig.

Saving my pennies to upgrade one day to Rohloff 500/14


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Re: Big mid-drive motor, bypass IGH?

Post by john61ct » Apr 25 2020 5:13am

Relevant thread, frame I'm considering

viewtopic.php?f=9&t=105606&p=1549521#p1549521

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Re: Big mid-drive motor, bypass IGH?

Post by Tony01 » Apr 25 2020 5:29am

Yup sprocket on the disc mount. Two problems:

1. Practically all gas motorized bike hardware relating to rear chain is going to be a half inch pitch, usually for 415 or 420 chain.

2. An IGH is not designed for motor use. So whatever little 10mm axle in it is going to break or bend with too much power. And that is not an easy or cheap thing to replace on an IGH.

If you’re dead set on going IGH I’d run it as a jackshaft like on a trike and figure something more robust on the rear. Too much work though.
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Re: Big mid-drive motor, bypass IGH?

Post by john61ct » Apr 25 2020 5:38am

Tony01 wrote:1. Practically all gas motorized bike hardware relating to rear chain is going to be a half inch pitch, usually for 415 or 420 chain
Not sure how that pertains here?

The Lightning Rods use #219, apparently cheap but strong kit from the world of gokarts?

> 2. An IGH is not designed for motor use

The point of this thread is exactly that, as in the title, I want the left-hand chain drivetrain to "bypass" the IGH since its torque is too high.

So only the pedal chain - human power only, completely separate drivetrain - goes through the IGH.

So, with that clarified, is this bit still relevant?

> If you’re dead set on going IGH I’d run it as a jackshaft like on a trike and figure something more robust on the rear.

No idea what a jackshaft might be, but I'll google it.



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Re: Big mid-drive motor, bypass IGH?

Post by john61ct » Apr 25 2020 6:08am

OK, learning happening I think.

I had thought "fixie" means only one gear, but in trying to figure out what a jackshaft is, came across

Sturmey-Archer S3x 3-speed Fixie Hub w/shifter

and discovered that (afaict) "fixie" is just the opposite of freewheeling / freehub, no coasting, when the wheel's turning so are the pedals?

So, not relevant strictly speaking, except (maybe?) for the topic of regen, which I want very strong when needed, for drag braking a heavy load on long steep descents, and ideally variable.

Is it fair to say I would want my left-hand "motor only" drivetrain to be "fixie" style in its connection to the rear hub? Rather than a second freewheel/freehub as I was originally envisioning?

In which case might need the GMAC/Phaserunner style "electronic freewheeling" with the LR motor, running it all the time at low power while pedaling in order to overcome the rolling drag and "feel like" it is freewheeling?

Hopefully getting the power lost back from regen as Justin claims.

_______
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_______
back to researching what jackshafts are 8-D



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Re: Big mid-drive motor, bypass IGH?

Post by john61ct » Apr 25 2020 7:21am

Came across a random comment to figure out later

tandem crank

https://www.bikeforums.net/11808309-post21.html
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Re: Big mid-drive motor, bypass IGH?

Post by john61ct » Apr 25 2020 7:23am

So, these are aka jackshafts ? http://sickbikeparts.com/shift-kit-and- ... e-products

Or something else. Seem to be designed for ICE motors????

Heresy!

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Re: Big mid-drive motor, bypass IGH?

Post by dogman dan » Apr 25 2020 7:51am

Yes, look at stuff meant for ICE motors, for what you want. It will be fixie, meaning the motor always turns if the wheel does. It will drag some while coasting, but like hub motors, you can just tickle the throttle with a tiny bit of power, and then it will coast freely. Very little use of power, but if you go to zero throttle, you will get a mild form of braking from the motor. Much like the engine drag while coasting a car in gear. But you can still have electronic braking with that setup too, which can be very strong.


The big advantage of this setup, is you can choose a gear ratio that suits your needs. Very low gear for slow speeds, but getting huge weights up hills, or faster and more motorcycle like power. Your choice, depending on motor size and gear ratio chosen.

I don't know your needs, but for a low speed high weight setup, I'd look at generic chain drive brushless scooter motors that can run easily in either direction. You can have regen with this, and reverse too. Put the sprocket on the left, and then a big sprocket on the wheel. There are rigs that bolt a sprocket to the spokes of a wheel too, btw. Its all in the gasser stuff.

It doesn't need to be as complicated as it could be, no offence guys, but he may not need anything more than a cheap gasser has.

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Re: Big mid-drive motor, bypass IGH?

Post by Rassy » Apr 25 2020 10:43am

Just a wild thought John, but it seems a strong front hub motor with a slow speed wind would do everything you want without all the complexity. Of course you would need a non suspension strong fork with good torque arms.

Certainly not recommending you go this route, but it would eliminate worry about free wheels, jackshafts, the weaker axle of an IGH, and the ability for electronic braking.

Anyway, good luck with your project.
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Re: Big mid-drive motor, bypass IGH?

Post by john61ct » Apr 25 2020 2:06pm

Such discussions for other threads, so many divergent paths let's keep this thread to the OP scenario:

400-500lb tandem / cargo, Rocky Mountain style climbs, 15mph top speed is fine if needed, max 25 so long as not compromising low-rpm torque for uphill standing starts.

Lightning Rod Big Block is the only motor being considered here, trying to get a handle on HowTo

Goal: (if not already default) get the motor's left hand chain working "as a fixie" so getting strong regen, single speed is fine for now

IGH is only driven by the pedal chain on the right side, I guess freewheeling (or freehub) is standard vanilla there.

I am happy to keep it simple as possible within that context, reliability / longevity are top priority.

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And if it is at all related to the above, trying to get a handle on the "jackshaft" concept. Core idea so far seems to be "alternative drivetrain, non-standard power transmission" between motor and wheel?

So to further clarify:

Jackshafts can be either fixie or freewheeling?

These "Shift Kits", Sick Bike seems to be "the" vendor?

Are they considered jackshafts themselves ?

Or they **include** a jackshaft?

IOW jackshafts can either be single speed or facilitate shifting?

Using an IGH "as a jackshaft" but mounted off the wheel? Seems to be a DIY hack to get a transmission?

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Re: Big mid-drive motor, bypass IGH?

Post by Tony01 » Apr 25 2020 2:38pm

john61ct wrote:
Apr 25 2020 5:38am
Tony01 wrote:1. Practically all gas motorized bike hardware relating to rear chain is going to be a half inch pitch, usually for 415 or 420 chain
Not sure how that pertains here?

The Lightning Rods use #219, apparently cheap but strong kit from the world of gokarts?

> 2. An IGH is not designed for motor use

The point of this thread is exactly that, as in the title, I want the left-hand chain drivetrain to "bypass" the IGH since its torque is too high.

So only the pedal chain - human power only, completely separate drivetrain - goes through the IGH.

So, with that clarified, is this bit still relevant?

> If you’re dead set on going IGH I’d run it as a jackshaft like on a trike and figure something more robust on the rear.

No idea what a jackshaft might be, but I'll google it.
Well you said mechanically bypass. So I inferred direct drive so you could use regen. Running a disc mount sprocket would mechanically bypass it but the hub axle itself isn’t suitable for power like the LR BB.

So yes you’d need to find a sprocket for the motor.

I didn’t mean the SBP setup. IMO that is a stupid setup but lots of people like it. Guess they don’t like engine braking. By hub jackshaft I meant the way rear hubs are used as a jackshaft in trikes or pedicabs. In the rear triangle where the rear wheel would be, pedicabs have a rear hub with an output sprocket going to a rear differential. Doing this would allow you to select your rear hub just like everybody with a gas bike does. Some people like to spend $160 or more on a solid hub; I like moped rear hubs.

IMO an IGH has no place next to a powerful motor.
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Re: Big mid-drive motor, bypass IGH?

Post by john61ct » Apr 25 2020 2:59pm


Tony01 wrote:Well you said mechanically bypass.
I meant that the power from the LR BB mid-drive is transmitted to the rear wheel through its own left chain (not the IGH used by the pedals).

Thus no mechanical connection, but the control of the mid-drive may be based off PAS

> So I inferred direct drive so you could use regen.

I never heard of a mid-drive called a "DD"; I thought that just meant hub motors, which are not included in the scenario here in any form.

I have concluded for regen the mid-drive power train needs to be "fixie", so if that is synonymous with your use of "DD", fine.

> Running a disc mount sprocket would mechanically bypass it but the hub axle itself isn’t suitable for power like the LR BB.

Aha. Do you mean that of every IGH including Rohloff's?

> So yes you’d need to find a sprocket for the motor.

Sorry I don't know what that means. The LR kits look like they are designed to be complete, don't they include all sprockets needed?

Is what you're talking about a big challenge?

> I didn’t mean the SBP setup. IMO that is a stupid setup but lots of people like it. Guess they don’t like engine braking. By hub jackshaft I meant the way rear hubs are used as a jackshaft in trikes or pedicabs.

I do not know anything about how either of those work, nor mopeds nor gas powered bikes, if you can point to learning resources I'd appreciate it.

I definitely want regen.

I also know nothing about pedicabs nor solid vs moped style hubs, but here this thread is about the pedaling drivetrain using IGH, so let's set that aside for now.

> IMO an IGH has no place next to a powerful motor

Do you mean even if there is no mechanical connection between them? Even on separate wheels? Why?




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Re: Big mid-drive motor, bypass IGH?

Post by john61ct » Apr 25 2020 3:10pm

If the axle strength really is a major issue here

do others agree it is?

note that Rohloff offers a QR hollow axle vs a threaded axle which I infer is solid and therefore stronger.

As a whole the assembly is rated for 130 N.m but that is based on shear pins, acting as "physical torque fuse" to prevent damage to the more expensive parts,

I would think the next weakest bits would be gearing, not the axle?

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Re: Big mid-drive motor, bypass IGH?

Post by thepronghorn » Apr 25 2020 3:25pm

Single speed means no gearing. You can use a freewheel at the back, or you can use a fixed sprocket which would be called a fixie. Since you want regen, that means no freewheels in the system.

Lightning rods' two stage drive (2 gearing stages, 1st stage is belt, 2nd is chain) has a freewheel inside the big pulley, so you probably don't want that one. His single stage looks like it does not have a freewheel, so that should work for you.

As far as the strength of the IGH goes, the disc brake mount should be able to handle all the torque a disc brake normally would, so I wouldn't be too concerned about driving the left side of an IGH.

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Re: Big mid-drive motor, bypass IGH?

Post by john61ct » Apr 25 2020 4:15pm

thepronghorn wrote:Single speed means no gearing
Well there is gearing, size of sprockets chosen etc, you just can't shift.

The LR system apparently makes it pretty quick and easy to swap the front sprockets out for different ratios / uses or terrains.

> You can use a freewheel at the back, or you can use a fixed sprocket which would be called a fixie. Since you want regen, that means no freewheels in the system.

Well, no freewheeling in the **motor** left-side drivetrain anyway.

Since the pedals' drivetrain (human powered only) is through the IGH and neither is involved with the motor, I believe there can be freewheeling in **that** system on the right side correct?

> Lightning rods' two stage drive (2 gearing stages, 1st stage is belt, 2nd is chain) has a freewheel inside the big pulley, so you probably don't want that one. His single stage looks like it does not have a freewheel, so that should work for you.

Wow great thanks for that, I will need to learn more about those details.

> As far as the strength of the IGH goes, the disc brake mount should be able to handle all the torque a disc brake normally would, so I wouldn't be too concerned about driving the left side of an IGH

Aha great thanks I thought so, must have come from Tony's mistakenly inferring that the motor would be driving the IGH.

_______
So, here is my hopeful understanding, please correct me if any of it is wrong:

The LR kit rear sprocket usually mounts to a disc brake mount on the left side, and modern IGH are usually designed so that is straightforward.

There is no freewheeling mechanism there, and in order to get regen I need to ensure Mr L Rod sells me a kit with none elsewhere, so that whole left-side system is fixie. (Would "fixed" be generally understood for that meaning, I'm irritated by that bit of jargon for some reason)

On the normal drivetrain, right side, IGHs include freewheeling, and the pedaling system will connect there, functioning completely independently of the motor fixed left side system.

But the power output from the two systems will be additive over some overlapping ranges of cadence, wheel rpm and torque required.

This combination can be created mostly from pretty standard OTS parts and is pretty straightforward with some help from a decent bike shop and maybe a bit of custom fabbing by a machine shop.

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Re: Big mid-drive motor, bypass IGH?

Post by thepronghorn » Apr 26 2020 12:28am

Yeah I think you understand everything. The term "fixie" really only applies to pedal drivetrains in my experience - I'm not sure there's a term for "non-freewheeling mid drives" besides just calling it what it is.

I'd say the hardest part about a left hand drive is chain routing which gets even more complicated if you are using a bike with rear suspension. The chainstays have to be narrow to clear the pedal cranks before they flare out to accommodate the 130+mm rear hub. Running the chain through there if you want to put the motor/jackshaft above or below the bottom bracket is difficult. I'm interested in the solution of putting the motor/jackshaft in front of the bottom bracket, but it's a pretty long chain run at that point which I've read is susceptible to chain drops. One example of this configuration would be district9prawn's linked below.

viewtopic.php?f=6&t=96754

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Re: Big mid-drive motor, bypass IGH?

Post by john61ct » May 13 2020 7:39am

relevant thread

viewtopic.php?t=106182

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Re: Big mid-drive motor, bypass IGH?

Post by Smoke » May 16 2020 1:02am

When I looked in to regen, it seemed like it could potentially dangerously overcharge a bicycle battery pack.

Be careful to get a controller that is smart enough to set limits for regen voltage and current.

I don't see any reason why a left side fixed sprocket drive on an IGH would be a danger to the axle.

However, a smaller wheel like a 20" BMX style will require more rpms and less torque to put down the same power at the same speed so you could reduce the mechanical stress at the hub/axle by going smaller and gearing to match.

When it comes to gearing, every stage comes with a hit to the efficiency. If you can do a single stage of reduction (small motor sprocket, large wheel sprocket, no jackshaft), you will probably be more efficient. One thing to look out for is sufficient chain wrap around enough teeth on the motor sprocket, if you go too small with a lot of torque you could have chain wear or stretch issues.

I have heard the Strumey Archer 3 speeds are pretty tough. I haven't heard that about the 5 speed. If your controller can do pedal assist, 3 speeds might be plenty.

There is a lot to think about for this but you should be able to make everything work together if you choose parts wisely. The first thing I would think about is brakes if long downhills might happen. Make sure you get that right before you work yourself in to a corner.

I once had a front brake explode in the middle of a descent and would have had to bail in about 20' more if my rear brake hadn't held together. Your probably going to be a 400+lb missile going down hill, if your stoker pedals at the wrong time you could pick up more speed than you can deal with. Maybe you should look for a front hub that can take two rotors? No tubular tires because you will melt the glue.
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Re: Big mid-drive motor, bypass IGH?

Post by john61ct » May 16 2020 5:39am

Smoke wrote:When I looked in to regen, it seemed like it could potentially dangerously overcharge a bicycle battery pack.

Be careful to get a controller that is smart enough to set limits for regen voltage and current.
Yes, if this turned out to be an issue in reality (unlikely IMO) ideally I'd figure out how to divert the regen output to big resistors out in the airflow or even water cooled if necessary.

Battery BMS is also involved, if the controller does not handle the scenario well.

The ability to effectively drag brake continuously is certainly a critical need, not relying on only one system for that.

And completely separate from the hydraulic hard / full stop-braking, no electronics to be relied on for that.

> I have heard the Strumey Archer 3 speeds are pretty tough. I haven't heard that about the 5 speed. If your controller can do pedal assist, 3 speeds might be plenty.

I'm thinking Rohloff, both for greater strength and the wider range. In this case no connection to anything electrified, human pedal power only.

I need to be able to limp home when batteries are empty or the complex stuff fails, rather than abandoning the vehicle and all my stuff to walk through an empty desert landscape.


> Maybe you should look for a front hub that can take two rotors?

Don't even know what that means, could you expand a bit?

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Re: Big mid-drive motor, bypass IGH?

Post by Smoke » May 16 2020 12:40pm

Motorcycles typically have one rotor on each side of the hub and a caliper on each.

Twice the weight, twice the brakes makes sense to me.

If you do direct drive with pedal assist and no freewheeling, limp home only requires you to remove the left side chain. Any limp home is going to suck so it's a balance of mechanical simplicity vs. electrical simplicity and when you are willing to tolerate annoyance.

In my mind, an ebike is almost always complex electronically so adding a bit more with a pedal assist system is not going to impact reliability very much. Tales of free freewheels exploding are pretty common so I lean toward electrical complexity.

I would push for mechanical simplicity, lower stress and well proven parts, then buy electronics that are well suited to your purpose and make sure the wiring is done right and your install does not create any unnecessary stress on the wiring, switches, sensor and battery. Then carry the tools you might need for a roadside repair. If pedal assist fails, be able to make it throttle only. If your whole system goes with a motor, controller or battery failure, be prepared to remove a chain. A two legged kick stand might make sense so you can drop the rear wheel to remove the chain. It's not a big price for mechanical simplicity.

Oh, the regen, it could be trying to dissipate several kilowatts of power. Trying to do that with resistors would require huge resistors if you wanted a drag brake for long descents. Everything I saw suggested that it would be an issue and it is mostly a BS feature used to sell ebikes because consumers expect to see it in the specs for an EV.

You can try it but I bet you'll be underwhelmed or break something.
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Re: Big mid-drive motor, bypass IGH?

Post by Rassy » May 16 2020 2:34pm

I played around with plug braking in about 2005. The platform consisted of a cheap mountain bike with poor brakes and a pusher trailer with two brushed 36V hub motors. On every ride I had to start by going down a quarter mile hill with up to a 15% grade and ending with a sharp corner at the bottom.

I used some basic 800 Watt relays to either connect the controller output to the motor or connect the motor to 12V headlight bulbs all activated by a simple double throw toggle switch.

Worked great, except I had to use the brakes to keep the speed below 15 MPH so the voltage produced would not blow the bulbs.

Replaced the bulbs with 35 feet of 22 gauge wire wrapped around a plastic pipe for each motor, which also worked great at any speed.

However, the relays used to connect with the resistance did not like being disconnected at too high of voltage which was created at speeds over 20 MPH, and the relays eventually welded the contacts together.

abandoned the plug brakes and replaced the bike brake pads with the salmon colored Kool Stop pads which did an adequate job for my needs at the time.

that bike was replaced with a delta recumbent trike with rear mechanical disk brakes which eliminated my braking issues.

Conclusion: I agree with Smoke that plug brakes and regen are more trouble then they are worth. Good disk brake systems are not only simpler and more dependable but also allow you to incorporate a freewheel in your propulsion system so you eliminate the motor drag when you either want to or have to pedal without assistance.
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viewtopic.php?f=28&t=88536&p=1291260#p1291260

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