Ball bearings you say? 3D printed BB crankcase.

Jason_WI Thu May 21, 2020 2:29 pm

Chevy Chase said it best in Fletch.

Ball bearings you say? 3D printed BB crankcase. 7df1a710

The last few weeks I’ve been working on a 3D printed ball bearing crankcase for the TD 049. I’m using glass fiber Zytel. This is like the 5th revision of the crankcase. Mostly for looks and getting the fit correct.

Ball bearings you say? 3D printed BB crankcase. 06dcca10

Ball bearings you say? 3D printed BB crankcase. 81391010

Ball bearings you say? 3D printed BB crankcase. D67af110

I have to use an aluminum insert for the threads. Kinda like the Testors 8000 plastic crankcase shown here.

Ball bearings you say? 3D printed BB crankcase. B5a7dc10

The problem I’m having is JB weld and Belzona 1111 are not holding the insert in most likely due to the heat. I’m knurling the ring for grip and also have pockets in the crankcase for epoxy to hold the insert tight.

This video shows the insert coming out as it runs.

I might use a combination of rings and knurling for the insert. The concentric rings would prevent the insert from coming up. This would only work if the epoxy doesn’t get soft.

I’ve been looking for a different epoxy to use. Need something that bonds plastic and aluminum at high heat. Even looking at furnace cement as an option. It can handle 1200F.

More pics.

Ball bearings you say? 3D printed BB crankcase. F3767210

Ball bearings you say? 3D printed BB crankcase. 8b426110

Ball bearings you say? 3D printed BB crankcase. 18b82810

balogh Thu May 21, 2020 3:07 pm

Jason how about cutting a thread - deeper and with larger pitch than on the cylinder neck- on the external surface of the aluminum insert, and tapping a thread in the 3D crankcase neck too? Those threads would retain the insert during engine operation..

**Cribbs74** Thu May 21, 2020 3:22 pm

Man Jason, you have the coolest ideas!

aspeed Thu May 21, 2020 4:05 pm

I am sure you are aware of the threaded locking inserts. Might work but it is a really oddball size. https://ca.images.search.yahoo.com/search/images?p=threaded+locking+insert&fr=yfp-t&imgurl=http%3A%2F%2Fwww.threadtoolsupply.com%2Fassets%2Fimages%2Fstainless-steel-key-locking-thread-inserts.jpg#id=0&iurl=http%3A%2F%2Fwww.threadtoolsupply.com%2Fassets%2Fimages%2Fstainless-steel-key-locking-thread-inserts.jpg&action=click

NEW222 Thu May 21, 2020 6:52 pm

Without knowing anything about the material you are printing with, as well as the wall thicknesses of both the ring and the printed case, is there a posibility that you can say drill a couple very small holes through the case and insert to 'pin' the ring in place, but not drill completely through the ring the cylinder threads into?

However, it looks great!

fit90 Thu May 21, 2020 7:24 pm

Could ceramic work with zytel or any of the other materials available to you? A ceramic coating might be a possibility. You may need to use some type of threaded insert unless you have an adhesive than can bond zytel and aluminum. Your work is very cool!

dckrsn Thu May 21, 2020 7:34 pm

NEW222 wrote:Without knowing anything about the material you are printing with, as well as the wall thicknesses of both the ring and the printed case, is there a possibility that you can say drill a couple very small holes through the case and insert to 'pin' the ring in place, but not drill completely through the ring the cylinder threads into?
However, it looks great!

I was thinking along those lines, using 2 or 3 cup head set screws. Huh...

The area around the cylinder base would have to be beefed
up a bit, I guess.
Printing parts has me fascinated. Thanks Jason. bounce

Bob

Dave P. Thu May 21, 2020 9:05 pm

Jason you blow my mind with the things you come up with. That is just too cool! I have no idea how to secure the cylinder, but I have no doubt you'll come up with a solution. Hat's off brother! Beer Cheers

Jason_WI Thu May 21, 2020 9:57 pm

I’m using 5/8” aluminum tubing for the insert. I ream the inside to .500 then tap with the 17/32-40 tap. I was so hoping the epoxy would hold. With a glued in insert I can time the cylinder to the crankcase.

I can try a threaded insert. I have .082” wall on the cylinder mounting of the crankcase. Any bigger and I would need to make cutouts for the mounting screws on the beam mount. I still need to find an epoxy that will lock the insert in place. It could back out when removing the cylinder.

Can throw all these ideas out the window if someone uses an electric starter with it flooded.

Not much material for a set screw unless I add a mounting boss for more threads. Maybe small long dowel pins at the long angle and a groove in the insert that the dowel pin fits tight in.

I did turn a drive plate but didn’t use it. I didn’t like the way the face knurl turned out. It does finish off the look though.

Ball bearings you say? 3D printed BB crankcase. 5392ed10

Ball bearings you say? 3D printed BB crankcase. 87b1f210

Ball bearings you say? 3D printed BB crankcase. A8db9210

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Ball bearings you say? 3D printed BB crankcase. 02957110

Ball bearings you say? 3D printed BB crankcase. 846e7910

**Cribbs74** Thu May 21, 2020 10:05 pm

This might be your best idea yet. More RPM and lighter weight!

I would consider using red loctite instead of epoxy for the threaded insert. It’s pretty tough stuff and used in extreme heat and pressure environments in the auto world.

Jason_WI Thu May 21, 2020 11:05 pm

I don’t know about weight savings. It’s 1 gram heavier than a standard TD.

I’ll look into using retaining compound. It’s green loctite. Not sure it will work on Zytel though as I looked at a data sheet of it earlier.

smooth_bill Fri May 22, 2020 1:31 am

Jason,

Just amazing programming and printing! Clapping

Have you considered JB Weld for the cylinder threads? That stuff is amazingly strong when set, and nearly impervious to crankcase temperatures. Just shim for the desired cylinder depth, press the welded threads into the case, rotate to the desired exhaust port orientation and let it cure. If it works, no need to replace the cylinder/piston until worn out. Replacement is needed at that point anyway.

Might require a guide to hold the cylinder vertical during the cure?

Do you plan on selling these? I doubt I could afford one in any case.

Good luck with the engine!

Bill

Jason_WI Fri May 22, 2020 2:11 am

I can't take all the credit for the looks of it. 1/2A Nut did provide a lot of feedback on looks and design through many PM's. Many thanks to 1/2A Nut for his time.

This was my first design.

Ball bearings you say? 3D printed BB crankcase. First10

1/2A Nut Fri May 22, 2020 3:27 am

Thank you Jason,

I am always happy to help, aesthetics is a big part of why we love these little engines.
Badging when possible is the icing on the cake after form and function. Jason did a
great job making the mods as the quest continued.

Here was some of the mods that led to where the design is today.

Ball bearings you say? 3D printed BB crankcase. Bb_cc_11

Ball bearings you say? 3D printed BB crankcase. Bc_1111

Ball bearings you say? 3D printed BB crankcase. Bb_cc_10

With bearings props will spin with less vibrations this will add power reduce
heat. When the engine is running at it's stabilized thermal state the upswing
will be a leaner mix producing more power. Threaded insert will solve the last
step in getting a running engine. This was realized after the first bench test
a while back. The current insert was modified for a second chance at working.
The vid posted shows it still can't take the pounding. Loctite makes a high temp
thread locker that should bond to the material with suitable results.

Small Cox Logo

coxaddict Fri May 22, 2020 4:18 am

I like the backplate design, maybe you can make a metal retainer to clamp the cylinder insert down using that design. Just an Idea.

getback Fri May 22, 2020 6:50 am

Looking really good Jason and Brad , you may want to look into this product only thin is it don't give heat range ? i would contact them if were me .. https://www.henkel-adhesives.com/us/en/products/industrial-adhesives/retaining-compounds.html Small Cox Logo

Do you know what the heat is coming off the engine at failure ?

1/2A Nut Fri May 22, 2020 7:10 am

I have 638 used it up to 50.4k rpm

getback Fri May 22, 2020 7:45 am

1/2A Nut wrote:I have 638 used it up to 50.4k rpm

On what part / sounds like it would fill the bill Small Cox Logo

davidll1984 Fri May 22, 2020 10:44 am

for insert is it posible to change desing of crank case to aling two top end cap bolt of back plate place on top not on side to alow longer bolt to retain cylinder insert wil look difrent but it wil hold just fine just dril tap after part is insert plus ad materiel on part u save weight alredy programing of part wil have to change no sutch glue wil hold just build case on the insert part insert it self need machining not just tight fit it nead to be part of case it self wit no chance to move bolt wil just ad strenght to insert y saw 2 way posible to work have to change case its not aloy u play wit so copie of engine is no no it wil need biger case insert wit diferent case chape on top case for the two insert retaning bolt hope u chage design for best result keap good work y wil want 1 for my colection price not isue for me

1/2A Nut Fri May 22, 2020 10:06 pm

Driveline steel shaft to steel sleeve.

Jason_WI Sun May 24, 2020 9:57 pm

5/8-18 outside and 17/32-40 inside threaded insert. I need to change the crankcase to print a 5/8-18 thread then clean up with a 5/8-18 bottom Tap.

Ball bearings you say? 3D printed BB crankcase. A95f8210

Ball bearings you say? 3D printed BB crankcase. 413c0810

Also need to order some threaded inserts for the 3 backplate screws.

Brass Heat-Set Inserts for Plastic, 2-56 Thread Size, 0.157" Installed Length

https://www.mcmaster.com/94459A240

I’ll need to make changes to the crankcase to use these.

1/2A Nut Sun May 24, 2020 10:38 pm

Looks like a good direction to hold that cylinder down. Inserts for
the backplate will make for a trend. Positive traction ahead.

Small Cox Logo

balogh Mon May 25, 2020 5:15 am

Jason_WI wrote:

Jason,

this is an unbelievably elegant upgrade to the TeeDee ..apart from the 3D crankcase, I saw you have produced a new 3D fuel nipple for the RC carb that, with its threaded (?) brass nipple, promises a much better longevity than the stock all-plastic one that is notoriously breaking once you touch it with some determination....

Will you produce such fuel nipples separately for Bernie or Matt to sell, too, or, you plan to package the crankcase with the RC carb components for a combined sell? (Either way, I will be a customer for sure, unless you decide not to sell them, that would be a great sorrow for many in the COX community... Sad

)

aspeed Mon May 25, 2020 7:37 am

I've never seen those brass 2-56 inserts before. I guess they are a new thing, or I don't get out much. Interesting how a soldering iron locks them into place. The carb nipple could just be a 4-40 standard nipple, or whatever size works. I have done that on LA carbs a few times.

balogh Mon May 25, 2020 8:01 am

It is the 3D nipple body with sufficient thickness that, combined with the brass nipple, will last much longer than the stock COX RC nipple. When the fuel stub breaks off - and it will sooner than later- from the stock part, there is no way to replace it with a threaded brass nipple because the plastic sleeve is very thin.

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Ball bearings you say? 3D printed BB crankcase.

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cool nice job jason

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