Again, thanks for catching that. 

Here is the one I changed to. http://www.omc-stepperonline.com/ratio- … p-140.html This is only 34mm long motor. So i'll get another 6mm of clearance to play with. Plus the weight ought to be better then even the solidoodle stock motor I am assuming.  The whole package weighs in at 380grams not including the extruder.  And it's $5 cheaper. 

Now I should go track down a 6mm ID hobbled extruder gear for those who want to do the upgrade and don't have access to a lathe.

Thanks for saving my skin again. An 8mm shaft would have been a MAJOR pain to deal with.

I have lots of enthusiasm.

Best quality to have really
And don't sweat it - we all get lost in specs sometimes

Well then time for me to call customer service and get my order changed...

Thank you so much... I have lots of enthusiasm. Sometimes less brains.

The front fan would work fine, mainly because the idea is to prevent the filament from softening whilst also cooling the motor as well - but this bit is kind of secondary. The motor is normally cooled so the stepper case can't radiate heat the filament causing it to soften and have feed issues - so if you active cool the filament then 'all is good' and you can forget the motor (within normal limits of course).

If you go bowden - then you can have 'easy to print' gears like a wades with herringbone cut gears quite easily - or yes do all manner of things with the planetary box... you just need to get some decent push-fit connectors (you can improvise with nyloc nuts et al - but they do come out, usually the middle of a print, where as quality push-fits correctly matched to the PTFE size will give you no troubles)

Which is good because I have been meaning to finish up my eggbot project that's just waiting on me to get another stepper...

I suppose there is the danger that there supplied motor's shaft is not 5mm, or that the gear that connects it to the the planetary gear box is an interference fit. Which wouldn't be the end of the world for me because I have an arbor press for such challenges. But again more work.

As far as the length, again that's with their assumed motor.  After measuring the solidoodle motor I believe it comes in at about 40mm as opposed to 48mm.  Couldn't get a precise read, in the middle of printing some filawinder parts.  But the stock solidoodle fan assembly still may prove problematic interference wise.  However on the Solidoodle 4's I've noticed they got rid of the aluminum heat sink in favor of putting a fan to the side of the extruder up front.  Perhaps because of the new metal extruder, adequate heat dissipation?  So I suppose as I make that aluminum mk5 variant I talked about no problem following suit with my fan. 

But regardless, not quite the "no fuss" swap out I thought I had found, but pretty close, especially for the price.

I do have a bunch of PTFE tubing on it's way thought so I might just ditch the whole carriage mounted setup and convert to a Bowden.

Weight; 520g. And you haven't added the extruder assembly (good thing its plastic!)
That weighs more than the whole Bulldog + Extruder assembly which is 495g - something to be very mindful of on the already overtaxed X and Y-Axis (unless you plan to upgrade those steppers too?)

Also:
Motor Length     48mm
Gearbox Length     27.3mm

Without the extruder, its 75.3mm's - The bulldog front to rear is 80mm including extruder assembly.
And don't forget the fan on the back of the extruder - unless you plan to work out some sort of blower setup and go underneath the motor as well ?

Anyway - on the right track and if you tighten up those lengths and weights you might be onto something - but a fair way to go yet before it fits and works on a solidoodle comfortably comparably to other off-the-shelf options

Since you may need hard to find length M3 socket head bolts you could always use M3 all thread with nylock nuts, cut to required length.

I ordered one, and we'll see how this bad boy works out.

http://www.omc-stepperonline.com/ratio- … p-140.html 6mm shaft dia. 380 grams (the one I ordered)

http://www.omc-stepperonline.com/ratio- … p-141.html 8mm shaft dia. 410 grams

The stepper would drop in,  but the holes on the front of the gearbox are a different pattern so you would need to redesign the extruder.

If so I will be venting via an exhaust tube to the great outdoors... my children can thank me later for contributing to the hole in the ozone.  Anyhow perhaps that will solve smell issues. 

Of course that still won't solve not being strong enough to handle the torque... Of course the one benefit to laser cut lexan over FDM ABS would be that the lexan would be at it's peak strength since it's not being put down in .1mm layers, and therefor no delimitation issues.

As far as cutting nylon, according to this it will, just melts badly--whatever that means--i'm guessing deformed edges which would be less then ideal for gears.  http://www.pololu.com/docs/0J24/3

Perhaps a better solution then fabricating our own transmission is harvesting one from an all metal transmission from an inexpensive DC geared motor. Perhaps one like this...http://www.ebay.com/itm/3-6V-DC-Small-M … 2c5f441e02

Or this is probably not going to have the acceleration we would need, but use this motor for a direct drive extruder, but since it's geared you get the resolution and hopefully enough torque to make an ultra compact extruder... I'm thinking it's not going to have the acceleration you'd want, but not wanting to track down the data sheet for it, I just ordered one to play with. for $4 it'll be a good toy to have around for some other project.  It has 64 steps per revolution. But with internal gear reduction included the equivalent of 4096 steps per revolution.  I am guessing it's plastic gearing inside... But maybe metal.  I'll find out in a few days;) Anyhow this strikes me as quite an elegant solution if it can meet the torque and acceleration requirements.  I am pretty confident it will meet the torque requirements, but speed not so sure. Of course backlash I am assuming will most definitely be an issue with such a stepper motor, but nothing our good old hysteresis firmware compensation won't handle with ease. http://www.ebay.com/itm/380803233237

My final thought is that the super cheap drills... Take it apart and harvest the gearing in that. I've done that for a few projects, and it turns out to be a wonderful source for a cheap (typically) all metal planetary transmission with in many cases built in adjustable over torque protection, not that you would want that in this case.

Nylon would frankly make a better gear. I don't know how suitable it is for lasercutting though.