Sometimes I have strange thoughts. Was thinking about a direct 1:1 drive transmission. Is it possible to say get a T5, remove all the extra gears and lock it in 4th? Added bonus if reverse can work also. Because someone will question gearing and all that here's my argument that it'll be fine.
23 inch tires plus a 4.10 rear end gives me 116 mph at 7000 rpm redline. Vehicle weight under 1200 lbs. So doing math it's the equivalent of a 3600lb vehicle with 3.35 first gear and a 3.67 rear end.
It could work but it won't be efficient. It's sort of like a top fuel dragster's transmission, they just slip the clutch up to 200mph+.
You should check out friction disc transmissions, an early form of CVT:
https://www.hemmings.com/blog/2013/03/14/smooth-going-with-friction-drive/
It would work, but think about your speed at idle. You're going to be slipping the clutch on every start until you're at least up to that speed. If idle is 700 RPM, that means you can never have the clutch fully engaged below 11.6 mph.
If you really want a trans that doesn't shift, think about basically making a single speed auto (complete with torque converter). Use the converter at low speeds, engage the lockup clutch the rest of the time. Only downside would be a bit more complexity and rotating weight.
I'll be there with Cheetos and beer to watch you load it on a trailer.
In reply to Robbie :
That's why I have a come along and a young son.
In reply to rslifkin :
Hadn't thought of that but this would be a pretty dedicated build. I'm not concerned about low speed drivability as much thinking about having a 2000-7000rpm power band.
Fair enough. My real question is if you are leaving reverse and something to select gears with, why not also leave 1st or 2nd in for parking? What is the weight penalty? Like 2-3-5lbs? And it will be darn near the center of mass of the car so it's about the least bad 5lbs you could have.
That said I see no reason you couldn't tear most of the guts out of a t5.
Stampie said:Sometimes I have strange thoughts. Was thinking about a direct 1:1 drive transmission. Is it possible to say get a T5, remove all the extra gears and lock it in 4th? Added bonus if reverse can work also. Because someone will question gearing and all that here's my argument that it'll be fine.
23 inch tires plus a 4.10 rear end gives me 116 mph at 7000 rpm redline. Vehicle weight under 1200 lbs. So doing math it's the equivalent of a 3600lb vehicle with 3.35 first gear and a 3.67 rear end.
That is basically what I do with my TR4A with a Rover V8. It has a T5, and I normally start in 2nd gear and end up in 4th. In 4th gear, the car will go from a rolling start to 100 very quickly, almost like driving an automatic. I often will not bother to shift unless I have to come to a complete stop. My car weighs 1900 pounds, on a 1200 pound car, that could work, but might be a little hard on your clutch
Circle track 2 speed transmissions used to be just 3 speed manuals with first removed.
Now they are pretty high tech. I like the feature where the clutch is built into the countershaft. No flywheel needed except for a ring gear for the starter, and the way they are designed, when you shift into high gear the countershaft stops rotating. Absolute minimal rotating inertia.
We used to get Saginaw three speeds and have the unused gears turned down. We couldn’t remove them completely because of how the transmission is made. They aren’t cheap but BERT Sprint Car boxes might be what you want to look at. They’re small, light and basically a direct drive box and tiny clutch.
In reply to Robbie :
It’s not just the static weight of the gears but the effect of them rotating. Cutting them down allows the car to accelerate faster.
Further to Wallys comment:
If it's an IRS vehicle swapping the differential for a transaxle would add minimal weight. If I was going to build a bike engine cart, for example, I'd use a VW transaxle in the back and then daily driving could be using the bike transmission with the vw in 4th but autocross maybe 2nd or 3rd on the vw would be more appropriate. Plus reverse would be a plus.
Other than that, maybe a Fluid Drive flywheel for low speeds?
I’ll add the powerglide aswell since if you run one without a converter it operates just like the Berts aswell. They both will ofcourse use a reverse clutch meaning the clutch is only used in low gear and reverse and unlike a conventional clutch these clutch pedals are used to move the car rather then the gas pedal when in low or reverse.
If the question is CAN you do that, YES, for sure. No question about that.
If the question is should you do that- that's a totally different debate.
In reply to alfadriver :
If you only knew all the things I do that I really shouldn't.
My problem with the automatic trans is weight and complexity of conversion. Since it's me I also thought it was assumed it needs to be on the cheap.
Just thinking other wacky thoughts, how about one of those AWD car based rear axles that are 1:1 drive and just use an old truck gear box?
Isn't this how benmodified has one of his crazy contraptions set up? I think is the bus?
I always thought 1:1 drive with a highish stall torque converter would be pretty great for a EM autox car.
Stampie said:Sometimes I have strange thoughts. Was thinking about a direct 1:1 drive transmission. Is it possible to say get a T5, remove all the extra gears and lock it in 4th? Added bonus if reverse can work also. Because someone will question gearing and all that here's my argument that it'll be fine.
23 inch tires plus a 4.10 rear end gives me 116 mph at 7000 rpm redline. Vehicle weight under 1200 lbs. So doing math it's the equivalent of a 3600lb vehicle with 3.35 first gear and a 3.67 rear end.
If you want reverse, you'll need to leave most of the guts in the 'box. You'll only be able to remove the unwanted gears from the third motion (output) shaft. That's not much weight saved for all the trouble. Keep in mind the length of the output shaft is determined by some of the parts you contemplate removing, so a substitute would be needed to maintain the gear stack length. You really should look elsewhere, maybe a different lighter trans.
I just can't imagine the effort, and running the engine at low of an RPM in certain spots, is going to pay off.
nocones said:Isn't this how benmodified has one of his crazy contraptions set up? I think is the bus?
I always thought 1:1 drive with a highish stall torque converter would be pretty great for a EM autox car.
It's the Daihatsu Hi-Jet pickup with the SBC and an in-and-out box.
z31maniac said:I just can't imagine the effort, and running the engine at low of an RPM in certain spots, is going to pay off.
It's only low rpm if you're going slow. Honestly the usage would be like running a whole autocross course in 2nd gear. I'm not looking for stop and go traffic driveability.
In reply to Stampie :
This sort of thing is why you can gears in the 6s and 7s for Ford 9".
At least, I could swear I'd seen 7.17 gears available.
https://pitstopusa.com/p-4121-bert-transmission-technical-guidelines.html
this shows the operation of a Bert or converterless powerglide. Need to get to 20mph to shift into high gear. You want the spend as little time as possible in low gear as it’s a very small cutch it can cause excessive wear.
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