B1M-4, bolt in mid motor 4WD conversion

[mk-Zero]

Okay, I have project ADHD (as most of you most likely do )! RIght now I'm working on releasing the B1M, starting the Ten4.1, looking at making a graphite version of the B1M (have yet to start a thread on that one... coming soon), and now I'm (as of last night) officially working on a 4WD version of the B1M. It will still be bolt in, like the B1M kit, and will utilize Ten4.1 driveline up front.

With the 4-gear MM layout, the top shaft is rotating the correct direction to drive the front 2-gear Ten4 gear box. So since the B1M has the slipper on the left side of the car, the drive belt and pulley will go on the right, no problem. Here's my first "mock up", which is me holding a timing belt gear (printed one for Ten4.1 mockups) about where it will go on a pan with a B1m transmission

So the big challenge with this is making a brand new V2 slipper top shaft that's extended on the side opposite the slippper, to drive the pulley. So I got busy on my lathe and mill and made one.

Slipper on one side, extended shaft with two flat spots machined in for a pulley on the other, and the gear will go somewhere in the middle.

I'm looking at buying pinion shaft gear blank of the appropriate spec (48P x 20T), and I'll probably shrink fit them on the shafts and/or pin them.

Obviously it will need a brand new tensioner system compared to the Ten4 too, but that's no big deal.

As with the Ten4.1, I'll probably offer a one-way front pulley with this one too. It will just be flopped compared to the Ten4 one since the belt will be on the opposite side of the car.

More to come

[GoMachV]

Your going to have to do some math on the pulley size if your running off the top shaft. The idler in a trans typically doesn’t matter, your math is dividing topshaft and diff gear. However, the idler is a reduction off the topshaft when used to drive the front. You are loosing some reduction so you’ll have a smaller pulley or a larger front pulley (but I doubt it will fit)

[mk-Zero]

Hmm, you are correct! I may have to make a new gear for the top gear of the front gear box. Not too big of a deal. Same gear blank as the new rear top shaft, which is a much simpler shaft compared to the rear one. And it's smaller so it should free up some space.

[Chewbacca]

Ever since someone posted his idea of the "MipKin" RC10 :
LINK

My main issue was how to get past the mid motor with the belt.

I was considering 2 complete stealths with extended top shafts, but never really started the project.

Now with a 4 gear in the rear, an 2 gear up front, things look promising.

BUT is the top shaft on the 4 gear high enough to clear the motor once mounted?

Obvious options are:

use a 380 sized brushless motor
a short can (out)runner (?)

Anyway I am curious to see this progress!

Nice work

[mk-Zero]

I plan to route it over the motor with guides, I *think* it can be done. Hopefully I'll have a chance to do some more mockups this week to verify.

If there's not enough room I can probably stand the trans up a bit more, thus raising the top shaft, but of course my preference is to use the same transmission case, bulkhead, etc. as the B1M

[mk-Zero]

Okay, it's going to work. I did a quick mockup on my B1M test mule. The belt will clear the motor no problem, it will just need to be routed diagonally up for a short distance:

Once I saw that was going to work I just stuck a couple top shafts about where the guides would go to get an idea of the belt routing. From those pulleys/guides it will make a gentle downward slop toward the front gear box pulley. There may or may not need to be another tensioner or guide up front.

[mk-Zero]

The pinion gear blank (one foot) came in today, so I spent the evening making a gear for the extended V2 slipper top shaft. First though I had to make a bushing for a collet to hold the gear, since it's OD is an odd size. Anyway, here it is, pinned to the extended top shaft I made previously.

Now I need to make another one for the front transmission. The shaft on that one is much easier though, since it doesn't need to accommodate a slipper.

[Chewbacca]

Looking good.

Do you know yet what you will mount the pulley to?

[Chewbacca]

at one point I was also considering 2 90 deg. gearboxes and try to connect the front and rear via shaft drive, but all of that was just theory, I never pursued it....

Like THIS

Depending on the bevel gears inside you have to watch forward / reverse between front and rear.....

[mk-Zero]

Looking good.

Do you know yet what you will mount the pulley to?

Thanks. So far I'm thinking there will be an aluminum plate of some sort that the gear box screws go through, kind of like a motor plate, that they will be mounted too. Or maybe printed nylon.

[JK Racing]

Just to make your mind spin....modify the bearing places for the top shaft to accept a 5X10/11 - then use 5mm shaft stock & 5mm pinions (from short course/8th scale) like the top shaft in an Ultima/Optima No need to create special gears, just modify your printed case to accept the pinion & metric bearings. Same for the front case as needed. Understanding the case will need to be wider to accept the pinion VS the top gear on a current shaft...But this will be 4wd specific, no?

[mk-Zero]

Thanks for the idea Joey. Jeff has suggested the same thing at different points. Are those gears 48P/20 deg pressure angle so they are compatible with the RC10 diffs and idlers?
Either way, I still need a custom extended shaft that can take a v2 slipper on one end, like the one one the right here


I guess not having to machine the gear from gear stock would save me some work, but most of the work and setup time goes into the shaft.

[JK Racing]

Yes, I believe our 48 pitch pinions are the exact same as the trans internals. Your extended upper shaft stays the same, minus length & 5mm diameter. Just tossing out ideas. My idea also involves modifying the case, so I will guess making the gear is an easier proposition overall...

[mk-Zero]

Making the gear from the gear stock isn't too bad, a little work on the mill and lathe is all it takes. And brass machines like a dream.
The shaft is much more involved, having a couple different diameters, some flats, and a 5-40 threaded section, out of stainless steel, which is notoriously difficult to machine.

[jwscab]

Brian, you should consider machining the shafting out of tool steel in an annealed condition, w1 or o1 machines nicely and holds it's tolerance if you decide to temper it.