Dune Bug-E 

Front-End, Drive Train - Part 4 ...

April 2010

Part #3 saw the last of the framing with a couple of simple body panels, a few coats of primer and lastly an attempt at Camo Paint...

I was stumped on how I wanted to address the drive train, especially with regard to Fwd/Rev, and incorporating a level of flexibility such that the Dune Bug-E could be a fun trail machine and still have enough low-end grunt that it could haul Venison, firewood, stones and even do some light field work like cutting and raking hay.

The above was just not realistic given that I didn't want to get into a complicated motor controller design and I was thinking that I'd be using the axel assembly that was part of the original drive-train.

One night literally just as I was drifting off to sleep I woke-up with a start, and remembered this Massey Ferguson garden tractor carcass that was behind the foundry.

I knew it had a gear-box, but was unsure if it was mechanical (ie; actual gear-trains to drive the axel) or hydrostatic.

The shift lever was frozen solid, so I spent a few days trying to identify the model on the web and came to the conclusion that it was in fact a Mechanical gear-box AND was originally coupled to a 12 to 14HP motor.

Unfortunately we got close to 30cm of snow between the time I thought of the tractor and the day I opted to pull the rear-end.

A bit of shovel work and it was ready to be liberated and hauled back to the shop.

It took an entire Walter Zip-Cut to finish the job, largely due to the awkward work-space to access the frame.

It took 2 days for it to thaw.

I drained about half a liter of water along with the thick blackish brown jizz that was supposed to be the gear-oil.

The box is now dry inside & out, and the shifter revealed 3 forward gears and 1 reverse.

The input pulley and one of the hubs are setup with simple pieces of tape, and the gear-box is put through the paces manually to determine what the ratio's between input & hub were for each of the 4 possible gear selections. 

1st - 30:1  CCW-In = CW-Out

2nd - 17:1 CCW-In = CW-Out

3rd - 11:1 CCW-In = CW-Out

Rev - 21:1 CCW-In = CCW-Out

This looked like a fantastic solution, in that it addressed just about every driving type scenario I could envision, all in a heavy cast iron block that weighs some where between 75 to 100lbs.

After consulting a handy print-out of the K96-4006's operating parameters, I ran some numbers through a spread-sheet to determine what kind of torque and top-speeds could be expected between the various gears. 

The exercise was largely aimed at determining the gearing between the motor and the gear-box.

After running a number of various sprocket sizes between the Motor and the Gear-Box I settled on approximately a 3:2 ratio and ended-up buying a 22 tooth sprocket for the motor and a 14 tooth for the gear-box. 

As counter intuitive as it may seem, the fact was that I wanted to step up the speed of the input shaft of the gear-box due to the massive 30:1 gear reduction of the Massey Ferguson trans-axel.

The first detail to be addressed was to fabricate a fixture that would allow the 3 bolt hub of the axel to mate to the 4 bolt pattern of the wheel rim.

One of my daughter's was visiting home from school, so I capitalized on the "free labour" of her boy friend as I'm not really big on making polite strained conversation while I have shit to do...

The boy proved to be quite handy and didn't fuck anything-up, which is about as much as I can say about anybody that dates one of my daughters.

Actually he did quite well and definitely saved me a day's labour...

The trick to making the plate adapters is to determine the center-point and work outward marking and drilling the holes, and with a circle cutting jig, work inwards with the last step being the hub center removed.

This went on for close to a week, emails to friends & fellow builders, postings on the Endless Sphere EV forums, with the intention of determining if this would work.

The drama of the gear-box choice was that it would require a custom swing-arm assembly and would close the door on ever using the factory axel if this didn't work out.

The answer came when I finally sold the 250cc liquid cooled engine and the deal became contingent on the inclusion of the axel.

In amongst the various correspondence that was flying about, the issue of brakes came up and I resolved to deal with it immediately before even starting the swing-arm assembly.

Infact what was going on was the classic "Chicken-Egg" conundrum cloaked in the guise of a "Motor-Mount/Swing-Arm" paradox.

As long as that war was raging in my mind I was glad to be distracted by the mundane of re-assembling the front-end and cabin.

It took maybe a day or two to get the seats back in (removed and installed with the 4-point harness properly bolted down) and even a small acrylic windscreen. Even though it cost close to $40, it probably won't last long as it developed a small crack while drilling one particular hole, and now I have concerns that it is prone to shatter on impact, so could be less than ideal from a safety perspective. 

The brakes were bleed and appear to be rock solid, though where there used to be the 2 caliper's up front and a caliper on the rear axel, it is just the front now and rear braking will have to be addressed with the controller.

Ultimately it dawned on me that I HAD to build the motor mount BEFORE the swing-arm assembly.

Luckily the Engineering staff that I dealt with at Advanced DC Motor's thoughtfully included a few PDF files when they dug-up the specs on my motor.

I disclaim to have no financial interest in ADC Motors nor to have received any gratuities or considerations "in-kind", but that is a company that is #1 in customer support! 

And likewise have heard the same thing from other EV builders on the web that they are wiling to go the extra-mile with customer support.

The 1st step was to translate some 1/4" plate into a few crude shapes.

The materials were measured, drilled and test fitted a number of times before I felt comfortable committing them to 3 dimensions.

I have to admit that I'm a little intimidated by the prospect of counting on my arm-chair engineering to hold this unit together, given that every motor-mount I've ever build before has always bent or broke and required at least one if not two revisions to get it all straightened out, and those applications were just a fraction of this size (physically & electrical power wise).

The swing-arm assembly curiously has no still images beyond this near the end of it's assembly and the 2 below...

Ultimately I decided to integrate the motor mount into the swing-arm as a structural component.

All square tubing is a solid 1/8th inch while the factory Massey Ferguson framing is also 1/4" plate.

This shot is of the under-belly.

The chain drive is #40, the sprockets are the Weld-On Hub to Sprocket design found at most tractor supply type stores.

The red roller is a skate-board wheel that has been shaped on the lathe to guide the chain and take-up any slack (now that the motor mount is rigidly fixed in place.)

The chain tension is maintained with this spring assembly that was recovered from a Murray cutting deck.

As an aside the spring was heated to bright orange over the length of section that was threaded, to take the temper out and allow the die to cut the threads.

The shock placement may be welded in steel, but definitely NOT carved in stone...

The idea here is to set as rigid a ride as possible (even at the sacrifice of travel of the rear wheels).

The shocks have approx 3" of absolute travel when they bottom-out. If they were placed perpendicular to the swing-arm at the midway point between the axel and the swing-arm pivot the wheels would enjoy almost 6" of travel, though the shocks would be loaded at twice the equivalent weight than at the actual axel.

While these are placed past the axel by just less than 1/4 of the pivot to axel length and as such should provide roughly 75% of the available travel, but 125% of the same load capacity if placed at the axel. 

And all that relates back to my concerns about the geometry of the swing-arm (wide at the pivot-point & narrow at the shock mount) which is why there is so much steel between these two points... 

The month of March 2010 in eastern Ontario was unseasonably warm, I'm not complaining (just explaining that approx 4 weeks rests between the images at the top of the screen and this one.)

In fact it was such a nice day I had to let the Bug-E out to hear the birds and get some fresh air...

The next installment will deal with the selection and installation of the motor controller and related electronics...

In the meantime, you could watch the video below and that should kill 5min and 38 sec's while you wait!

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