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Learning how to build Lotus Seven replicas...together!
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PostPosted: July 13, 2007, 1:02 am 
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Joined: August 14, 2006, 2:09 am
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Location: Sacramento, CA
js it possible to build your own transmission case? I assume it wouldn't be THAT much more different than building a chain differential out of a car differential. I know it'd probably be easier to just make an adapter plate and whatnot, but it's just something that I was thinking about.


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PostPosted: July 13, 2007, 1:55 am 
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sure, just break out the Legos :lol:

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PostPosted: July 13, 2007, 1:56 am 
THAWA wrote:
js it possible to build your own transmission case? I assume it wouldn't be THAT much more different than building a chain differential out of a car differential. I know it'd probably be easier to just make an adapter plate and whatnot, but it's just something that I was thinking about.


It possible to do just about anything, but the tolerance on the internals of a transmission case are VERY tight. Many professional machine shops would have a difficult time holding them and they would charge major dollars for the effort. Expect to spend at least what it would cost to get a Hewland or Quaife racing transmission.

You would also need to duplicate the internal geometry of the transmission, unless of course you were going to design the gear train from scratch as well. But if you were able to do that, you wouldn't be asking about building the case. Without engineering drawings of the transmission internals you probably wouldn't get the case right, and you would soon get another chance to machine a case.

The transmission doesn't have a lot of unused volume inside, so any custom case would probably be just about the same as the original it replaced, but more expensive. You probably would not be able to save any weight over a modern transmission case without being significantly weaker.

If you are talking about just doing a custom bell housing to mate a transmission to a block for which it was not intended that is a far simpler and less expensive proposition.

There would be very little to gain from doing your own case, unless you want to bragging rights, which would be significant!


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PostPosted: July 13, 2007, 3:35 pm 
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Joined: January 14, 2006, 1:06 pm
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Location: Vista (north of San Diego CA)
How tough it would be depends a lot on the transmission too. My Pinto tranny gear case is basically a cast iron box with a sheet metal lid. If you are good with machine shop equipment and a welder, you could make one without doing anything exotic. As someone else said though, the tolerances of any milling on the front and back faces would be critical since they support shafts and bearings. There are some internal features also that you would have to weld up in the box which might complicate things a little bit, but it wouldn't be rocket science.

If your transmission is like my Suzuki Samurai tranny, duplicating it would require either some casting work or more involved welding and machining. The gear case on that tranny is two halves bolted together. Makes it easy to work on, but tough to duplicate.

All in all, it seems like a significant project all by itself. I'll stick to building cars and let someone else to the tranny's. ;-)

John


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PostPosted: July 13, 2007, 5:15 pm 
you could try casting your own too it's not that hard you just have to make a furnace which is time consuming but worth it if you make stuff


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PostPosted: July 13, 2007, 6:03 pm 
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Joined: August 20, 2006, 1:34 pm
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the question nobody has asked would be: WHY??

What is you intent? make it lighter? stronger? smaller?

dave


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PostPosted: July 13, 2007, 9:48 pm 
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I have no real reason, and there's a VERY good chance that I will never try this, but when I see how many chain diffs are home built I start thinking that it can't be that much more complicated to make a tranny case.


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PostPosted: July 13, 2007, 11:46 pm 
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I'm sorry, but I still don't understand. I mean, you could probably make your own basketball, too, but is there any point?

In your original post, you mention an adapter plate. Are you talking about making an engine/transmission combination that does not occur in nature?

Most any transmission can be mated to most any engine with a little effort.

dave


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PostPosted: July 14, 2007, 12:07 am 
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No, as it is, I'm already set on a tranny engine combo that is known to work. I'm not planning n doing any of this right now, I was just curious.


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PostPosted: July 14, 2007, 7:20 am 
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Thawa, you have a PM.


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PostPosted: July 14, 2007, 9:18 am 
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Joined: August 5, 2006, 11:04 am
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dmottaway wrote:
I'm sorry, but I still don't understand. I mean, you could probably make your own basketball, too, but is there any point?
dave


Considering you can buy a sports car, even a Lotus 7, why would you build your own? Because you can, because you want to make something different, because you want it to be all yours. This is just an extreme example of DIY, not necessarily practical or inexpensive, but doable. Also, as has been noted, the difficulty/practicality depends greatly on the original trans design. The2 sample designs (Suzuki and Pinto) differ greatly. There would be little benefit in making a new case for the Suzuki trans as it is already aluminum but for the Pinto you may save substantial weight. That being said I wouldn't do it myself but others may, YMMV.

David Tupper


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PostPosted: July 15, 2007, 12:23 am 
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"because I can" is usually followed by "and do it better".

was just wondering THAWA thought he could improve upon.

thought maybe he was wanting to use an tranny with an integral bell housing on an engine that was not a bolt up combination. new transmission housing MIGHT be a solution, but not the one I would try.


dave


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