Interest in Tera Low rebuilds

masnottuh said:

I recently rebuilt a Tera low 4:1 np231 kit, including machining new helical gears, rebuilding the planetary cage upgrading bushings to needle bearings, etc. The end product is essentially a brand new tera low kit minus the minimal wear items like the inner gear and input shaft.

My question is HOW MANY of these worn/busted tera low kits are actually out there? It's expensive and time-consuming for me to machine the helical gears and cut apart/weld the cages but if there are enough of them out there I can save $$ by increasing quantity. So, does anyone have a tera low in need of a new planetary gear assembly?

I'll attach a pic of a TL planetary assembly in case anyone isn't sure what I'm talking about

Background: I am a Ph.D. student in mechanical engineering with the ability (+resources) to rebuild these tera-low planetaries that fail frequently. I am trying to see if there is a reasonable demand for this service that would warrant me machining items in bulk.

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I have a TL in good working order. I don’t know how worn the planetaries are. I’m careful to run it according to the instructions because I’m afraid of failure.

If you can make new kits that are cheaper options than Midnight Metalworks D300 or an Atlas I'm game.

I'd love 4 1 ratios but not $2 to $3k plus love.

-Mac

Did you take any photos of the planetary you made?

I got my hands on one that had given up the ghost a while back. It was interesting to look through. It went to the metal scrapper years ago though. If I'd had a source for a new planetary or had any hope of one I'd have kept it.

Beyond the machining capability, do you have resources to test them? I suspect most that have destroyed one would probably rather have something they can treat like any other case rather than having to be a gentle lover with it.

The one I had came apart so bad the only useable part was the case. I have heard other similar stories. I just don't know if there is enough demand to make it worthwhile. The price will be a huge determining factor.

You seem to have picked a career path that suits you. I like to do real technical stuff too, like last night I swapped my oil drain plug for a new one.


Get the book “ One Good Turn.” It is the history of the screwdriver and screw, and it really follows mankinds path to precision manufacturing.

It’s a good read. You would enjoy it I believe.

freedom_in_4low said:

I suspect most that have destroyed one would probably rather have something they can treat like any other case rather than having to be a gentle lover with it.

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Never happen with that unit. The planetary is too small. The reason the Rubi planetary is so freaking huge is to keep the planet gear speed lower to keep from burning them up. Not that the Tera part doesn't have other issues but the main reason they fail is they are run in an overspeed condition that smokes them.

P man said:

The one I had came apart so bad the only useable part was the case. I have heard other similar stories. I just don't know if there is enough demand to make it worthwhile. The price will be a huge determining factor.

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The Tera planetary was around 650 to replace the part. I had buddies with the whole case half for sale for 750ish and couldn't talk other folks into buying them for spares. Yeah, I get you don't want to spend the money but there are no more parts from Tera.

masnottuh said:

I recently rebuilt a Tera low 4:1 np231 kit, including machining new helical gears, rebuilding the planetary cage upgrading bushings to needle bearings, etc. The end product is essentially a brand new tera low kit minus the minimal wear items like the inner gear and input shaft.

My question is HOW MANY of these worn/busted tera low kits are actually out there? It's expensive and time-consuming for me to machine the helical gears and cut apart/weld the cages but if there are enough of them out there I can save $$ by increasing quantity. So, does anyone have a tera low in need of a new planetary gear assembly?

I'll attach a pic of a TL planetary assembly in case anyone isn't sure what I'm talking about

Background: I am a Ph.D. student in mechanical engineering with the ability (+resources) to rebuild these tera-low planetaries that fail frequently. I am trying to see if there is a reasonable demand for this service that would warrant me machining items in bulk.

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Not sure where you are headed with this but if the thought occurs to make your own front case half, I have some really good resources to assist with that part.

macleanflood said:

If you can make new kits that are cheaper options than Midnight Metalworks D300 or an Atlas I'm game.

I'd love 4 1 ratios but not $2 to $3k plus love.

-Mac

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Has anybody even gotten their hands on one of those Midnight D300's yet? I am willing to spend that kind of coin, but I want to see one running in a TJ first.

mrblaine said:

Never happen with that unit. The planetary is too small. The reason the Rubi planetary is so freaking huge is to keep the planet gear speed lower to keep from burning them up. Not that the Tera part doesn't have other issues but the main reason they fail is they are run in an overspeed condition that smokes them.

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The size of those planets immediately jumped out to me when I disassembled it, never having seen one before. It gave me the impression that their primary focus was how to build it and didn't really think about whether it would work.

freedom_in_4low said:

The size of those planets immediately jumped out to me when I disassembled it, never having seen one before. It gave me the impression that their primary focus was how to build it and didn't really think about whether it would work.

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To be fair, Tera didn't do that design. They sort of borrowed it from a gent who was here in SoCal at the time if his story is to be believed. He didn't go over how he designed and where he got the planetary set up from but, Tera should have reworked it given the resources they have and bumped the size up a fair bit more.

I suspect the stumbling block may have been the concept to have an additional part to house the planetary unbolt from the front case half like the OEM Rubi case uses. It may have occurred to them to increase the size and then not been able to solve how to machine down inside the larger section to cut the bore for the ring gear.

masnottuh said:

I'd love to chat about a custom front half. The tera kit's main pitfall IMO is the small orbit radius of the planetary gears.
my email is [email protected] or if you have a preferred way to connect that's fine too

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I’d be interested.

I don’t have a Tera kit but I wish I had 4:1 in my 231! If you could fix the strength problem on these I bet a lot of us would be very interested… is there anything from the Tera kit that you can’t make?

masnottuh said:

do you remember if the inner gear (the circular one that the planetary assembly sits inside) was also destroyed? this is a difficult part to clone

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I'm sorry but I don't recall this was a few years back

starkey480 said:

I don’t have a Tera kit but I wish I had 4:1 in my 231! If you could fix the strength problem on these I bet a lot of us would be very interested… is there anything from the Tera kit that you can’t make?

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They don't have an inherent strength issue. They are plenty strong enough but they smoke the planet gears, bushings, and axle shafts they turn on when they get spun too fast. The only way to slow them down is to increase the orbit size, increase the axle diameter, increase the gear diameter or some combination thereof. That would make them look very much like the front half of a Rubi case.

Every part of the case can be made, the problem would be one of scale and how many you have to make to lower the cost to make it worthwhile.

To even begin to get the case casting to pencil out, you would have to do a run of 200+ and then hope that an underlying issue that you missed doesn't require a pattern rework. Just the pattern for that casting is in the 8-10,000 range to run on an automated casting line.

The main reason folks like Midnight do billet cases is they have a small upfront investment to start turning out cases. A few blocks of aluminum, machine tools and a good CAD program will get you going. The problem with that is no matter what you do, you can only lower the costs so far with economies of scale because you are always going to be slow in production, there is a lot of waste, and that costs money no matter how you dispose of it.

A high quality casting will blow those costs away. Cast to near net and you can machine 20-30 pieces in the same time as one billet case. Upfront costs are a lot higher though. Roughly guessing, if you don't have 60-80 grand to throw at the first run of cases, that's gonna be a problem.