Mark Bendys' Gocart page.
Well, this project started by seeing a mates backyard full of custom carts. Being a typical bloke, I knew I could do better, so the challenge was on. The size was going to be determined by 2 things. How big my lad was going to be when he would be old enough to use it, and it had to be narrow enough to fit out of my garden shed single door. I chose to use sq & rectangle tube, as it was easier for me to measure angles & cut with an angle grinder. Majority of the frame is made from rectangular fencing tube as I had a stack left over from previous jobs.
I bought the front wheels first from Paramount Browns fairly cheep. They have a cheep bearing setup pressed in already. The second thing I bought was some 27mm diameter solid round bar, and lathed it down to fit inside the front wheel bearings, and used a die nut to cut the M12 thread for the nylock nut to hold the wheel on. After the front axles were lathed, the backs were cut to the 6 deg camber angle, and a M6 thread tapped into the end so I could hold it still while welding the stub axle to the yoke. The yoke was 50 X 100 X 8mm C channel, that I cut 50 mm long.
|Cheep tyre & rim setup from paramount browns, with 12mm retaining nylock nut. Aprox $10 ea.||100 X 50 X 8mm C channel as yoke.|
The king pin was made from 27mm tube with a 5mm wall thickness. These were cut to 85mm long to fit within the 100mm C channel. I then used a 20mm hole saw in a separate 5mm steel plate. The washers produced from this, were de-burred, pushed into the end of the 27mm tube and welded. The pilot hole from the hole saw was then drilled to 12mm. To hold the yoke on the king pin, I used a M12 bolt (not a set bolt), cut the threaded part off, and just cross drilled a 3mm hole in the bottom for a split pin to go in. The king pin was welded to a square tube with 3mm wall thickness, which had been pre cut / filed to the 6 degrees camber. I chose 6 deg, as it was an average between a road cart and dirt cart. If you go to larger angle, the steering will be to heavy, but stable at speed. Too lesser angle, the steering will be twitchy at speed, but want to go around corners all the time.
To set up the caster angle (works for speed stability, straitening up coming out of corners, and in conjunction with camber) I welded up the kingpins on the end of a square tube as before mentioned. Then welded plates on at a 6 deg angle (with the top of the king pins facing backwards, towards the rear of the cart) that bolted on the the frame. I made it removable so the front end could be worked on at bench height, and it could be shimmed to change the caster angle either way.
Once this was done, I marked the position on the inside of the yoke to line up with the M6 thread I tapped in the stub axle centre. By doing this, you can hold the axle on the yoke in place when its welded.
|6 deg Caster angle. This plate bolts on to base of frame. Photo taken from front.||M6 CS thread through yoke, into back of stub axle to hold steady whilst welding.|
Now the steering arms need to be set up with the correct Ackerman angle. The Ackerman angle reduces front tyre scrub going around corners as the inner wheel travels a tighter arc. This angle is determined by pointing the steering arms to the center of the rear axle. Perhaps leave these until the rear axle position is worked out or axle is mounted.
|Steering arms, with Ackerman angle. Photo taken from rear, LHS.||Ackerman Angle.|
The steering arms are just M8 all thread or 8mm threaded rod. Rod ends were a fortune ($20+ each X4) from CBC bearings. If you look around, I'm sure you'd find something cheaper. I don't think they are necessary. I beleive you could make your own up. All the bolts in the front are hi tensile, with nylocks. Flat bar or angle with the holes drilled in the correct spots will do just fine. The steering shaft was from a crashed donor cart, and support for it was built to suit an adjustable height. The fake Momo steering wheel I bought from Bali 10+ yrs ago as a present for a mate, gave it back to me when he found I was making a cart. Thanks JOD.
Well, below are the specs for the frame. If I was to do it again, I would not worry about the narrow track to fit through a single door, and make it wider. Less tendency to roll over...... I started building the frame from the front. Front end & steering first.
When I worked out that I wanted the frame 330 wide (making sure I had enough space for the wheels moving for steering and to fit through a door frame), I tacked a scrap piece of steel across the back to keep the frame parallel. Once the front was finished, I didn't like how high the seat was above the frame. Hence widening of the frame to accommodate the seat within the rails. This was done by only cutting 3 sides of the tube, bending the 4th side, and only having to do 3 welds. The seat is a fiberglass cart seat. Again from an donor cart. I wanted to make the seat adjustable. I had some Brownbuilt perforated angle rail I welded underneath. It was just a matter of bolting the seat where it needed to go.
|Photo of finished painted frame.||Front top of frame.|
|Middle top & rear of frame.||Rear top of frame.|
Once I worked out how far back I wanted the seat, I welded a brace tube across the frame. The cross brace was aprox 390mm long. At least I know now, from here back is all the good stuff. More of that later...
Pedals are made from angle steel with plates welded for the actual pedal. An M6 threaded screw is placed through the frame to mount the pedal on. Place a nylon or any washer on either side of the pedal and hold on with a nylock. The cables for the brake & accelerator are the same as push bike brakes. I made up cups for the ends, and tubes for holding outer cable on the frame. They were just from M8 bolts drilled out all the way for tubes, and 2/3 for the end cups.
|LHS Pedal stop & outer cable guide cup from front.||RHS Pedal stop & outer cable guide cup from front.|
|Tubes made for holding brake & accelerator cables on frame||Mounted pedals with return springs.|
|Adjustable steering coloum.||Adjustable steering coloum.|
Now for the fun part. I picked up a OHV stationary motor with Maxitorqe clutch, chain and axle gear set. Unfortunately the exhaust manifold & flange had been pillaged, so I had to make one. When I get a moment, Ill rebuild the motor just to give it a birthday. Following photos are me trying to work out how to mount the motor, rear axle & brakes as close as possible to keep the carts wheel base as short as possible.
|Trying to decide where to mount everything.||Trying to decide where to mount everything.|
Well it was decided that I would mount it lower than the frame. The lower I went, the further forward I could go due to the back of the seat being tapered down & forward. I welded 50 X 8mm flat bar the full length of the back section of the cart. This was to strengthen the whole back end, and give the axle bearings something to bite into. The engine brackets were 50 X 5mm flat bar. Rear one had to be fancy to clear the drive gear & brake rotor.
|Engine mounts dropped lower than the frame.||Engine sitting lower between frame.|
|Engine mount clearing drive gear & chain.||Engine mount clearing brake rotor & thinking about caliper mount.|
Once I decided I could cram it all in, I welded in another 390mm brace to box in the rear area. Brakes had me baffled for a while. I bought a cable operated brake caliper & cables for a pocket bike, and had to make some again funky brackets to support it. Just hope they support the cart. The caliper & cables were bought from a cart / pocket bike stall at the Brickworks market, South road. This guy sells obsolete parts fairly cheep. The cables & caliper were $20 odd bucks.
|Brake caliper with 2 fabricated adjustable mounts.||Caliper & cable temporarily fitted.|
|Welded tabs on inside of frame & tapped M6 to mount floor.||Floor mounted. Photo from underneath.|
|Bottom mount for steering shaft.||Brake pedal assembly. Accelerator the same setup.|
|Steering up.||Steering modified again to go lower.|
|Front finally finished. If it looks toed out. It is! Still has to be adjusted.||MG red racing front tyres for the rear wheels..|
Rear rims are from Edwards Cart Wheels in Adelaide. If you ask for seconds, you will get it a fair bit cheaper for items that may have a small nick or scratch from machining process. One rim with valve, nuts / studs, and a 25mm hub. I actually bought 4 other rims & 4 cart tyres that I picked up second hand. I didnt use the second hand rear wheels & tyres as they were so wide they looked ridicules so I only used the 2 front tyres for the rear, one front rim with bearings for the rear, and picked up a drivable wheel the same size & 25mm hub from Edwards to keep it an open wheeler. This stops under steer. I bought the gear carrier second hand, & machined the brake caliper carrier. I would have been better off buying them from Edwards as seconds. Getting the tyres on the rims was an absolute bugger. I borrowed a cart wheel press to try to leaver them on, but in the end, succeeded using 2 blunt screwdrivers. The second hurdle was seating them. They had to be sitting on the edge of the seat on both sides before they held any air. Now, for me, this was the scary part. Having to pump them up to 95 psi for the tyres to pop on to the seat correctly. Only found this out after hours of bashing the tyre with a rubber mallet.
|Brake being assembled with 6mm keyway.||Rear axle being assembled.|
|Self aligning bearings for rear axle. Dont forget to do up 2X grub screws.||Axle gear & ally gear carrier with 6mm key way.|
|Motor sitting nice & low.||MaxiTorque clutch & DID chain.|
|First BIG balls up. Cut one to many links out of chain & brought axle fwd.||Everything nice & snug, with engine governor removed.|
Well, this is my first big balls up. I was trying to get things done quickly, and I cut the chain one link to short. The outcome was I had to bring the axle forward aprox 12mm. This caused the brake rotor to hit the rear engine mount. After the axle was square, and equally spaced, I locked the main bearing grub screws to stop the axle moving sideways in the bearings. Then inserted the 6mm key way & locked down the gear carrier to the axle. Next, adjusted the brake rotor, inserted 6mm key way, and locked it down. Next balls up was then the brake key way fell out sideways when I tipped the cart sideways to take some photos. Ill be drilling and tapping another retaining thread on top of where the key way sits in the carrier.
|Governor removed & custom linkages added.||Cable, air box, & filter added.|
I spent some time trying to start this beast, to no prevail. It had a black plug meaning previously running to rich. After a cleaned plug, still no luck. So I decided to pull the carby off and give it a clean / re-build. Bit of muck in the bowl, but that was it. Remember to use loctite to hold the butterfly on the spindle. Those screws have habit of falling into engines. I don't have a compression guage, so a quick check to see the valve clearances & push rods were ok. All seemed good.
|Carby rebuild after failed attempt at starting.||Checking con rods straight & valve clearance.|
|Extra M5 on keyway after it fell out before trial run.||.|
Well today we had the test run. Motor was nice & quiet. Had to turn down the idle as the clutch was already kicking in when it started. Well it may be small, but a 6.5 hp motor sure does boogie. Did a quiet lap to make sure brakes and everything worked. Well on full throttle I was getting wheel spin and on our course bitumen these soft race tyres weren't going to last long. Brakes were not as good as I expected, they were locking the wheel up. It was a bit hard to concentrate with juggling my 3 yr old lad on my lap hanging on to the steering as well. It was a bit twitchy at the higher speed, but that could be the length of the steering arms. Ive drilled numerous holes in the arms, so Ill be bolting it to a closer hole next time. Down side of this is it wont have a good turning circle. OR it could just be the cheep front wheels cause the bearings are poop. I never made top speed. Yes, I know, people who now me know Im mad, but I had my son on my lap! But Ill be using a gps to work out top speed next time. Engine is over kill. So overkill its not worth changing the gearing. It will just cause more wheel spin. So you just have to push the throttle down slowly. It would be interesting to see what happen if I make both rear wheels drive.
|Cart complete & after test run.||Comparing size to my 3 yr old.|
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