I hear you Pat... but, right now I have a train that runs ...I did not before. The spiders that are on there now are pressure (interference) fitted PETG. I can open up the bore a tiny bit more and use an adhesive anywhere from CA to something like the Locktite Max construction adhesive which would fill the spline. If I can keep it running until steel spiders are available... then, I'm good.
@Dennis-LaRock posted:I hear you Pat... but, right now I have a train that runs ...I did not before. The spiders that are on there now are pressure (interference) fitted PETG. I can open up the bore a tiny bit more and use an adhesive anywhere from CA to something like the Locktite Max construction adhesive which would fill the spline. If I can keep it running until steel spiders are available... then, I'm good.
Totally agree Dennis, …..I wouldn’t alter your file, I’d like to see how the longevity holds up, ….plus, I’m curious how much of a press fit your spider is??…..do you have to beat it on at present? Or simple push on?….that’s going to be the decisive factor in making these out of metal. I’ve had several parts printed in metal, and the material is very hard indeed. Very difficult to bore,…..Ideally, a fit with a couple love taps, and some loctite shaft retainer would be ideal, as this would be an at home DIY repair similar to what y’all have done now,……my son has one of these engines with a split spider, so when y’all decide what file to try, I’ll get a test run,…..naturally, the metal parts are going to be more expensive than plastic, but I’m hoping for the permanent fix ……heck, I might need to look into a 3D metal printer
Pat
Pat, I'm just guessing here... but, I lined it up with my fingers and gave it maybe around 2 pounds of pressure with the thumb to get it started. I then, used the but of the pin-vise to press it on, again with somewhere around 2 pounds to set it even with the bottom of the shaft. It was not a struggle it get it on. Not very scientific... but, it worked.
I wound up using a 2.28mm bore and cleaned the bore up with a 2.28mm (thank you Rod) pin-vise. I have an FDM printer so you will not get the pretty dimensional accuracy (detail) Rod can achieve with the Resin printer. However, its true, it fits and it works. I can send you some Spiders and the .stl files. If you need adjustments in the measurements that can be done in all of 30 seconds... and I could get you the new file pronto. If you are not using a resin printer it can be a little maddening trying to print these itsy bitsy spiders on an FDM printer.
Guys I have a bit of an update to throw into the mix. Today I pulled both trucks on the F3 and found the rear spider was split. It pried off very easily and the shaft splines showed evidence that the spider has been spinning. So I cleaned off the residue and slipped in a new spider and off she goes. The fit on the shaft is an easy press on type of thing. I used my thumb to get it aligned and started, then the round handle end of a screw driver to seat it flush to the end of the shaft. Easy push on, not near 2 pounds IMO.
To be honest I am not surprised about the split spider. Cured resin tends to be brittle and I guessed it would have very little resistance to being stretched. I am looking forward to getting some of your spiders to play around with Dennis, just to see if they have any better longevity. One thing you said caught my eye, the 2.8mm ream out size. My reaming has been done with a 2.3mm bit, half a mm smaller in size than your 2.8mm. A 2.8mm hole would just fall off the shaft in my F3. What am I missing? Are later shafts maybe bigger diameter?? 
(Dennis has since edited the erroneous 2.8 to 2.28, all good now!)
@Dennis-LaRock posted:Pat, I'm just guessing here... but, I lined it up with my fingers and gave it maybe around 2 pounds of pressure with the thumb to get it started. I then, used the but of the pin-vise to press it on, again with somewhere around 2 pounds to set it even with the bottom of the shaft. It was not a struggle it get it on. Not very scientific... but, it worked.
I wound up using a 2.8mm bore and cleaned the bore up with a 2.8mm pin-vise. I have an FDM printer so you will not get the pretty dimensional accuracy (detail) Rod can achieve with the Resin printer. However, its true, it fits and it works. I can send you some Spiders and the .stl files. If you need adjustments in the measurements that can be done in all of 30 seconds... and I could get you the new file pronto. If you are not using a resin printer it can be a little maddening trying to print these itsy bitsy spiders on an FDM printer.
Good idea, ….let’s do that, and I’ll do some more research based on you & Rod’s hard work, and get a few printed in metal for analysis work,….
Pat
Rod... good catch ...I left out a 2. I Bored and Reamed at 2.28mm. Old men have to cover each others backs/butts! I will correct the post above!
I'm headed up stairs to print out a fresh pile of PETG Spiders in Space Gray w/2.28 Bore. I will get you guys copies of the .stls with Bores from 2.28mm-2.3mm in .01 increments. Pat, if your measurements differ... just let me know and I'll get you a fresh .stl in a nono-second. Also, if you need settings for printing with an FDM printer... let me know.
The Nylon & Delrin were a bit trickier to print but I did get them both to adhere to the build plate and was able to print the Spiders. Slipperiness and installed shaft adhesion issues aside... the Nylon was too soft and the Delrin is the stiffest/hardest material I have printed with.
Dennis I should have picked up on the missing 2 in the 2.28mm right away. Duh. No worries. So with nylon being quite soft and delrin quite hard, maybe your original PTEG is the best compromise?
For the metal option I think Pat will want to know what ID to have them made in, rather than take a guess at it. I suggest let’s try 2.28 ID with the idea that it can always be reamed out to as much as 2.3 in order to get a nice tap-on fit if required. What do we think?
For material it seems like steel would be too hard. I would think brass is a nice compromise between machinability and toughness. It’s not like these things are highly stressed at all. As Pat said all plastics tend to shrink and get hard over time, and when they split they are done. Brass will make that a non-issue. But I am OK with whatever you guys want to do. 
Rod
@Rod Stewart posted:For material it seems like steel would be too hard. I would think brass is a nice compromise between machinability and toughness. It’s not like these things are highly stressed at all. As Pat said all plastics tend to shrink and get hard over time, and when they split they are done. Brass will make that a non-issue. But I am OK with whatever you guys want to do.
The metal you print isn't going to be as hard as steel I suspect.
@gunrunnerjohn posted:The metal you print isn't going to be as hard as steel I suspect.
I sure hope not!
Hardness is not an issue if you increase the hole size. With metals you can use retaining compounds that don’t require an interference fit.
Pete
@Rod Stewart posted:maybe your original PTEG is the best compromise?
Rod
If you pick up a plastic drink container/bottle it is more likely than not... made of PETG.
@Norton posted:Hardness is not an issue if you increase the hole size. With metals you can use retaining compounds that don’t require an interference fit.
Pete
Yep, …thank you ….that’s the point I was trying to make,….with a metal spider, hopefully we can get it to where just a couple lite taps with a hammer seat it with 640. Then after 24 hours, it’s concrete …..that’s the point I was trying to make ….
Pat
