Stealth Trans w/Gear Diff

[XLR8]

Perhaps consider using helicoils and machine screws, or larger brass inserts.

With plastics, I typically use CA glue in the hole. It lubricates the coil during installation and then locks it in place.

Another thought I had was to add a drop of blue thread lock to the underside of the screw head so it bonds to the aluminum plate.

Just be careful to keep the thread locker away from the plastic. It will attack and soften it, at least temporarily.

[XLR8]

With spring just around the corner, it will soon be time to get the buggies out again. I really want to finish this project and get the files to printer so this won’t be a wasted effort.

Looking back through the thread, I was planning have a gauge block printed to aid sizing the bearing bores but I never got around to it. Anyway, I believe this question has been answered before but perhaps it’s buried in another thread somewhere. The case halves will printed using MJF; can anyone offer some guidance on the printing process allowance to accurately size the bearing bores to achieve a snug press fit? thanks.

[GoMachV]

If you are hiring out the printing, you will need to print a gauge and see where it ends up. My attempt to use shapeways to print was around 5% out of spec instead of the .4-.5% they list but only on the holes, not the other measurements When I inquired they told me it was due to the process and to be expected. Their tolerance chart means nothing. The reprint in sls was also loose and I gave up on shapeways after throwing away $100 worth of prints.

[XLR8]

Thanks Jeff.
Yes, this is probably going to iMaterialize since I've had good results with them in the past.
From what you've posted and other have said, I believe there is a level of unpredictability regardless of which printer service one uses. Bearing bores require the highest level of precision (probably more than any other feature) so having a gauge made is probably the best route - although I feel there are no guarantees that the final print will be accurate and bearings will fit perfectly.
With the Mid cases I had printed a while back, I didn't allow for printing and the bearings simply would not fit and I ended up reaming the bores. Big hassle.

By the way, how's your latest conversion case coming along?? Your design looks like the best approach to fit a modern diff to the RC10. Any guess when they will be ready to ship?

[GoMachV]

I have a few prints I sent out for people to test and as with how things usually go- crickets. If you know anyone that will have the drive to complete it and test it in a timely manner lmk, I have a home printed case in cf-15 that should hold up plenty well for testing. With DR10 kits on sale for $99 on Amazon it’s a terrific time to buy one just for the trans

[XLR8]

Testing is good however I recall the production cases will be injection molded and about all that can be tested with printed cases is that everything fits together and it drives the wheels. You'll need molded cases for durability testing.
What sort of testing are you looking for?
That's a very good deal on the DR10. It includes a number of useable parts - which AE will eventually discontinue.

[GoMachV]

Just general test fitting in multiple applications at random to make sure everything is happy. Going directly to an injection mold is a very expensive first attempt for me anyway, if there was a gear circle off a little or a hole out of spec it would be a real expensive fix.

[JosephS]

I have a few prints I sent out for people to test and as with how things usually go- crickets. If you know anyone that will have the drive to complete it and test it in a timely manner lmk, I have a home printed case in cf-15 that should hold up plenty well for testing. With DR10 kits on sale for $99 on Amazon it’s a terrific time to buy one just for the trans

This is something I was not aware of until now. Thanks! Same $99 at tower

[silvertriple]

If you are hiring out the printing, you will need to print a gauge and see where it ends up. My attempt to use shapeways to print was around 5% out of spec instead of the .4-.5% they list but only on the holes, not the other measurements When I inquired they told me it was due to the process and to be expected. Their tolerance chart means nothing. The reprint in sls was also loose and I gave up on shapeways after throwing away $100 worth of prints.

Just see this... I had various prints done myself, but never by Shapeways, and while I had some out of specs elements for bearing cages in SLS, it never happened with my prints in MJF from Weerg, i.materialise and JLCPCB). And the parts I got from @optimaforever for my Samurai and the Sogun are the same : not a single issue in measurements for MJF. I had a chat with him the time I saw the SLS tolerances issue for the red parts on my Nichimo, and he stated SLS is less precise, and therefore when targeted for SLS he was adjusting the diameters accordingly...

That being said, the main reason for choosing SLS veersus MJF was the possibility of white parts to be able to dye them properly, and this is no longer needed as White MJF parts are now possible... I don't know for Shapeways (I'm not using their services as they are by far the most expensive), but I can't see reason why you would prefer SLS over MJF at this stage...

[XLR8]

Just general test fitting in multiple applications at random to make sure everything is happy. Going directly to an injection mold is a very expensive first attempt for me anyway, if there was a gear circle off a little or a hole out of spec it would be a real expensive fix.

Yes, injection molds can be extremely expensive.

Hey Jeff, can you use your CNC router to make a pair of side plates similar to what I’ve done here?
I’m assuming that your router is far more accurate than any 3D print.

The plates will provide a way to check your design (critical features like gear circles, bore diameters, screw hole spacing, etc.) and allow you to make needed corrections before sending your design to the molder. When the production molds are finished, the molder can send you pre-production inspection samples for you to verify they have accurately captured your design. If the inspection samples reveal some inaccuracy, the molder is obligated to make corrections – they shouldn’t charge you for their mistakes.

Anyway, it's just a suggestion to help you move your project to completion. I really want a set of your cases.

[silvertriple]

I've looked out for information on injection mold costs... All depends the material you want to inject, and the quantity you want to get from the mould... But in short, for small quantities, Formlabs advertise some high temp resin (glass filled) able to work out 10 to 1000 depending upon the injection temperature and the injection pressure... I remember having seen a webinar (formlabs again) with practical example of use of their high temp resin in the specific moulding targeted usage (you may be able to find this free webinar on formlabs website)... This might be worth to consider as SLA resin printer are far more precise that other printing process, allowing to build moulds for small series...

[XLR8]

I've managed to locate a spare printed idler pulley from the Mid (Polyamide MJF from iMaterialize).
The bearing bore measures ~7.9mm for an 8mm bearing so maybe I'll use 0.1mm allowance for my cases.
In any event, when the prints arrive, I will carefully measure the bores and document that for future reference - something I should have done before.