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Learning how to build Lotus Seven replicas...together!
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PostPosted: February 21, 2017, 3:38 pm 
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Joined: November 11, 2013, 4:47 am
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Location: No. Nevada
This should be good for any MC engine with a "Reversed" rotation shaft drive.
In my case that will be an FJR1300.
Get an 85-95 Toyota 4Runner diff section from the front axle.
No need for the ADD if you can find a diff without it.

This is the answer for my rear mounted FJR1300 engine project.
It would also work to create a front drive BEC or three-wheeler.
The FJR1300 output ends up on the right when the engine is reversed, the Toyo diff input is off-set to the right, so the diff assembly and engine both end up very close to centered.
Drive axles will be fairly short but since they use CV's and travel will be limited on a light road car I see no issue.
The 'Reverse" rotation FJR drive is corrected via the 4Runner FRONT axle, the R&P will have the thrust to the correct side of the gears. :mrgreen:

Not sure about the common 4.10 ratio but that can be changed if truly necessary.
No need for the car trans so weight will be saved where it really should be minimal.
Never found a true weight for an FJR1300 but I think it should be less than 300 pounds.

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PostPosted: March 2, 2017, 12:33 am 
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Joined: October 8, 2008, 12:22 pm
Posts: 199
Location: Austin Texas
Hi Richard,
For not-so-cheap way to add a reverse gear, the option of a LSD, and have the gearing you will need, have you seen this product?

http://eliteracingtransmissions.com/cat ... /mx200-il/

I haven't bought one from them yet, but if my other projects go as well as hoped I will likely be doing so in about one year.

Dean


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PostPosted: March 2, 2017, 2:33 am 
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Joined: November 11, 2013, 4:47 am
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Location: No. Nevada
£2200.00! :roll:
So far I'm into the Toyota parts a little under $100.00 :lol:
I'm going to perfect this before I make any more effort on the rest of the car.
At around two hundred pounds the FJR1300 engine is close to the original VW and I know the VW powered cars handled very well.
They were essentially street legal Formula Vee cars.

Hoping to have a mock-up pic soon.

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PostPosted: March 2, 2017, 10:23 am 
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Joined: October 8, 2008, 12:22 pm
Posts: 199
Location: Austin Texas
Hi Richard,
I like your ideas for the layout of the car, but what about the R&P ratio?

If what I find here is correct, the final drive ratio for an FJR1300 is 2.773. Can you get a R&P for the Toyota differential that will be close to that ratio?

https://www.google.com/url?sa=t&rct=j&q ... VA&cad=rja

Maybe a chain or belt drive is needed between the FJR output and the differential? If the Toyota differential has a 4.10 R&P then 16 and 24 tooth sprockets and a chain drive would match the FJR's overall gearing. Will your rear tires be about 24" in diameter?

Isn't this Ring and Pinion ratio issue the reason why many bike engine cars use a Ford Thunderbird/Lincoln MKVII differential, since higher ratio (low numeric) gear-sets are available? Running one of those upside down could work, but that may place the pinion higher than you would like.

I hope you find a good way to make it work, but I wonder if spending a few thousand on the MX200 might be worth the money in the end. Not having to purchase or build another means of having a reverse gear is a big help.

Dean


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PostPosted: March 2, 2017, 4:42 pm 
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Joined: November 11, 2013, 4:47 am
Posts: 579
Location: No. Nevada
Fighting a bad cold so have to stay away from the machinery as I'm fond of my fingers.

Doing more research on this.
Found an excellent source of parts.

Trying to verify the rumor that the Supra is basically the same diff for a cheaper LSD.
So far aftermarket gear sets have been lower than stock but I'm not done looking.

Did get a nice PDF exploded view this morning if I only knew how to post it.

EDIT: Looks like 3.07 may be the tallest gear available.
Need to look at my tires OD too.

EDIT 2: Seems the tallest available reverse cut R&P is 3.73
7.5" Supra diff is supposed to fit.
Looking at 26.57" Dia. tires on 15" rims for the rear.
If I can find the right calculator I may be able to see how much that helps.

The 4Runner setup has been used to create a narrow IRS center section for V6 and V8 use.
Since my car will be very light I am going to look at some other reverse cut R&P sets, Suzuki, Dana 30?
I may just have to make my own housing.
Hmm, if I'm going that far maybe add reverse too.
Would like to find a good Saab 900 free-wheel device to use in my reverse mechanism.
Going to try to finish repair of my CNC indexer, then I will be able to cut my own splines.

If I'm rambling blame the flu. :BH:

One more edit, then to bed.

Seems I may be better off to use a Dana-30 reverse cut R&P, 3.07 is readily available.
May be able to modify a housing, or just make one.
Aluminum Jeep 30A IFS is a disappointment as the right ratio is not available.
Since the car will be a little heavier than a bike I think 3.07 may be just fine and I really am not looking for 165 MPH in this car.
It sits so low it makes a standard 7 look like a lifted vehicle, but the Aero in not much better.

At least I am into the Toyo diff's dirt cheap so I can certainly get my money back.
May still make an IRS center from them by modifying for two short axles as posted at the top.

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PostPosted: March 3, 2017, 4:13 am 
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Joined: November 11, 2013, 4:47 am
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Looked up the specs of this FJR1300 powered 7, viewtopic.php?f=40&t=18204#p218135
He is very happy with a 3.54 rear.
Since I am going to want to stay in the power band while hill-climbing at fairly high altitude lower than stock gearing should serve me well.
3.73 might be just about right?

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PostPosted: March 26, 2017, 1:02 am 
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Joined: November 11, 2013, 4:47 am
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Location: No. Nevada
Put some more time into the 4runner diff project tonight.
Got one unit apart so can now verify that the ADD equipped units do use bearing for the stub axle, not bushings.
Also figured out that I can easily reduce the size of the ADD unit and lock the spine into place after removing the vacuum can.
Or in the BEC I could use the ADD as an emergency axle disconnect in the event the car got going backward. :idea:
Might even be able to wire it to a sensor for automatic deployment.
Reading threads here it has been stated many times that a BEC will suffer greatly in a rearward slide unless the clutch is pushed in very quickly.

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