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Learning how to build Lotus Seven replicas...together!
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PostPosted: April 13, 2018, 1:17 pm 
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Joined: August 11, 2013, 6:03 am
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Location: CNY
Cliff notes from the main build log found on HRCS:

Quote:
I've been conscripted into an escelating war.

My good friend asked for some assistance in making his daughters powerwheels truck the most capable vehicle possible, to give her an edge in the play time drag races.
Since I can't say no to making his kids smile, and am a speed nut, I of course accepted.

The need for speed resulted in a 24V conversion using two 12V group 16L AGM batteries in series for 24V.

In the name of safety, we also added a low tone car horn at the same time. Who am I kidding, it was to blow the competition out of the way. :P

This lead to a new GPS verified top speed of 10MPH in "high gear" with each motor getting 24V, with a few smoked factory motors as consequence.

Other problems that came to light were the severe lack of traction due to the rather ineffective blow molded hard plastic tires, and the dangerous yet fun abrupt on/off throttle and brake response. Power slides and donuts for DAYS.

Thus, a 24-48V motor controller with foot pedal was ordered in, along with a set of 13x5 pneumatic tube lawnmower tires.

A little work to the factory couplers on the lathe and some holes punched through the rims to attach the couplers made for a new set of rear tires.
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The back "axel" needed to be shortened by 2.5" to accommodate the new setup.

Because the factory motors didn't like the start/stop 24V torture and all of them went out in a melting mayhem of fun crushing proportions, in went a forward/reverse rotation set of Traxxas Titan 21 RC motors rated for 14.4V.

We also made some shaft spacers to fit the same tires on the front, but the change in scrub radius was too much for the janky steering setup that these have. Steering became too hard, and tended to snap full left or full right. The old hard plastic ones went back on instead to prevent a rollover.

One of the future steps is to install bulbs in the headlight and turn signal housings and wire them up for full function.

I ordered in a 24V wheelchair differential transaxle to replace the factory gearbox/motor combos and give some true capability to this thing. Also in the wings is a golfcart steering rack to provide some much needed maneuverability.

Quote:
The wheelchair transaxle is quite beefy, all metal gears, and looks to be easy to modify with longer shafts to get the track width out a bit more.

We'll be using MTD 20x8 rims since we have a few sets already.

The transaxel shafts are 20mm, turned down to 3/4" on the wheel ends.

We need to cut flats on the ends to fit the wheels on, and then we can bolt things together.

Should fit pretty good, and it'll clear the fenders nicely.

Shot of the transaxel after shaft removal.

Image

Wheel with the shorter shaft stuffed in.

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Quote:
Got the flats milled on the shafts Wednesday after work, forgot to take photos.

The shafts fit the wheels, but the bolts and washers I got to retain them went AWOL.

Looks like the next step is to make the rear half of the frame and decide on how the steering should be implemented.

I did get a 1.2m chunk of 20mm shaft material in case I decide to make some new shafts to adjust the track width.

One of the parties involved in the playtime drag races now has a gas powered cart, and rules were bent so so he can ride on the road (looooong story...), so the space race is on and the cold war is heating up.


Quote:
Small update!

The RC motors burned out a few weeks back, after a grueling few hours of continuous racing.

We went to mount the transaxle in, did some modifications, and came to the conclusion that plywood and 2x4 would not work.

The thing has enough torque with the existing controller that it was able to split the wooden mounting brackets.

Another issue is the existing controller does not have any provision for braking or regen braking, which is a safety concern.

I've got a VESC controller coming in from diyelectricskateboard which allows for true accelerator and brake inputs, regen braking, and will handle 50A with a small fan and heatsink.
Also ordered an 8 cell lithium pack rated 30V 27.2AH nominal. Quite compact at 11"x7"x3" and only 14.25 pound.

The frame build will happen as soon as we get the unibody from my friends place. Front is getting golfcart steering rack and gocart spindles, no suspension.

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Walt
06 RX-8 Shinka
04 RX-8 GT
06 325xi
Some people never have anything except ideas. Go do it.
Emissions & fuel economy haven't exactly been areas of strength for past rotary power plants, but absolutely no one with a soul has ever cared.


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PostPosted: April 14, 2018, 8:48 am 
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We are Slotus!
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Joined: October 6, 2009, 9:29 am
Posts: 7651
Location: Tallahassee, FL (The Center of the Known Universe)
I LOVE IT! I wanna see pictures of the little Darlin', with pigtails flying, blowing past the boys...


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JD, father of Quinn, Son of a... Build Log
Quinn the Slotus:Ford 302 Powered, Mallock-Inspired, Tube Frame, Hillclimb Special
"Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom


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