Well I apologize for not posting regularly. I've been doing work on the go kart, and a bunch of other stuff so it's been pretty crazy. I haven't been making time for the blog, I have a few posts worth of images backlogged, and there were more I should have taken.
Anyways, this weekend my Dad and I finished up the kart and my family got some test driving in. There were some minor snags, as expected, but all-in-all it was a great success!
The project will be going on the backburner for a little while longer so I can relax a bit.
Enough chatter, here's the link: http://www.youtube.com/watch?v=B2IlIuhWXRQ
Tuesday, May 22, 2012
Wednesday, November 9, 2011
Front axles, Frame, Welds
Front Axle Spindles
Here are the two finished spindle/fork assemblies which allow the front tires to turn. The spindle is 4" long and rotates in the fork, on a 5/8" Grade 8 bolt called the Kingpin. The kingpins will have a cotter pin installed at final assembly to keep the front wheels from falling off :) |
| Assembled spindles and forks - click to enlarge |
My initial assumption is reflected in Option 1, where the fork is welded to the frame and the spindle to the wheel. Somehow this option feels more natural for me.
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| Mounting option 1 |
However there is another alternative, actually inverted - the fork is welded to the stub axle and the spindle to the frame. The reason I am considering this option is because I will actually get more travel out of the steering this way.
With Option 1, with the Steering Arm welded to the spindle (on the face towards the rear of the kart) pushing outwards (turning wheel towards center of kart) is no problem, but when pulling inwards (turning wheel out) the Steering Arm will hit the fork, limiting steering travel.
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| Mounting option 2 |
Of course in both these images, the stub axle needs to be cut, and is shown with a KPI of zero (just for demonstration). On that note, however - my machinist friend (who has worked on race cars) tells me a zero KPI is perfectly okay - since this goes against everything I've read about go kart steering I will have to do further research, but am fairly sure I will still be including a healthy KPI in the final design.
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| Top view |
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| Steering mockup. Includes threaded rod with Heim joint, does not include Steering Arm from fork to Heim joint. |
Skipping past all sorts of design, measurements, ensuring everything is square and level (about 12 hours worth) here's the basic frame finished up. It includes the rear axle, motor mount, and narrowed section for the front tires to pivot into (See Top view, above)
Now I'm sure some are wondering why the motor mount plate is behind the rear axle. It's a straightforward answer - as with lots of things on the kart, it's a compromise.
At a #50 chain you need about 19 inches (center to center) between the rear axle and the motor's axle. Putting the motor in front of the rear axle means the the kart has to have a stupidly long wheelbase - motor & driver - which would cause a poor turning radius. The benefit would be that the top of the chain is tight (optimal) compared to the situation we chose where the bottom of the chain is tight (not quite as optimal but better than vertical or on an angle)
So we keep the kart a more reasonable length for steering and have less issues with chain tensioning as in a vertical mount system (engine above rear axle, which we seriously considered)
In the end I think it'll look a bit funny, but that is okay with me.
Sample welds
Motor mount plate welds:
The motor mount is 1/4" plate welded to 0.100" tubing. The thickness difference made welding interesting - I turned my welder up one setting higher for current and turned the wire feed up a bit. I carefully spend most of the time pouring heat into the plate before quickly detouring onto the tubing to make the joint, and repeat. I think they turned out really well.
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| I think this is the weld I'm most proud of. |
I'm not expert but I don't think I have anything to worry about here. It's possible I should complete all the weld beads, but I get the feeling that the current amounts are strong enough; this plate is not coming off.
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| Heat-coloured motor mount plate |
Frame front section:
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| 0.125" wall (all fully visible pieces) welded to 0.100" remainder of frame. |
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| 1/4" bar welded as a fillet inside the front section to help resist lateral forces. Welds appear disjoint because I did them in three sections to try to reduce heat warping (even with tack-welding) |
Frame height offset:
Not so obvious from the above pictures is the offset I have designed into the frame. It's goal is to ensure the center of the rear axle lines up with the center of the front axles.
Now I'm not sure exactly why that's important but I was informed that it is, and it sounds reasonable.
As you can see the rear axle sits about 1.5" from the top of the frame, so 2.25" from the center of the frame. If we extended this frame forwards the front tires would be 2.25" off the height of the rear tires.
Offsetting the forward section of the frame by one frame-width (1.5") gets us close to our goal without any complicated setup. The remainder 3/4" we plan to account for when welding the front spindles.
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| Frame offset - note the kart is unfortunately upside-down in this image |
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| Another view of frame offset |
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| As you can perhaps see the front tire (shown adjacent to rear tire only for this explanation) basically lines up with the height of the frame in the forward section. |
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| Same image as above with a different perspective. See how the axles can both be mounted in a reasonable fashion? |
Here's one last mockup of what she will look like, including the seat I purchased.
Please note that this mockup sucks, I hope she will be much more attractive in the end.
This week
-buying steel for seat mounting
-looking for a steering wheel and any additional steel for mounting it
-researching KPI further
-buy 0.045" tips for the 0.045" flux-core wire I purchased - neither my local Lowes or Rona carry them. In fact, Rona carries no welding supplies of any kind - a fact three of four Rona agents were unaware of. [Sigh, no, welding tips are not dangerous 'like bullets' Rona employees. No, I do not want soldering supplies. No, trust me, it's not in the "hardware" aisle, stop asking me to look there]
Thursday, November 3, 2011
Steering wheel spindles
So I was on the lathe again. The idea is to make a bushing that I can weld to my frame that will hold the steering wheel shaft in two places along the shaft, allowing it to rotate but holding it steady otherwise.
The shaft will have two 'washers' welded on either side of each bushing to keep the shaft from sliding through the bushings.
I started with 1.25" dia by 2" long solid bar. Faced and drilled out progressively to 1/2" as with the front axle spindles - mainly because 1/2" is the largest bit I happen to have.
Then I bored the hole larger, to around 0.65" all the way through. Finally I bored 1/2" deep holes into each end that are wide enough to house the 5/8" bushings.
Here you can see the progression from stock to finished product.
I will be cutting the bronze bushing (on the right) in half, putting half at the top and half at the bottom. Also you can see the zerk (grease nipple) and the hole which I drilled and tapped which will deliver grease to the volume around the shaft.
The zerk is threaded in, and the bushing halves were driven into the spindle.
The bushings are a little loose, as I am still finding it difficult to get precision results with the boring bar - it seems to flex in varying amounts which depends on how much material I try to take off, making all of my cuts inconsistent. e.g. 60 thou movements take off about 60 thou, but 40 thou movements only take off about 25 thou. Need to talk to a machinist about this issue.
Lastly here's the bushing with the steering column through it. Spins like a dream. As you can see I turned down the steering column to nicely fit the bushings - a most unpleasant task of which I have no pictures.
The shaft will have two 'washers' welded on either side of each bushing to keep the shaft from sliding through the bushings.
I started with 1.25" dia by 2" long solid bar. Faced and drilled out progressively to 1/2" as with the front axle spindles - mainly because 1/2" is the largest bit I happen to have.
Then I bored the hole larger, to around 0.65" all the way through. Finally I bored 1/2" deep holes into each end that are wide enough to house the 5/8" bushings.
Here you can see the progression from stock to finished product.
I will be cutting the bronze bushing (on the right) in half, putting half at the top and half at the bottom. Also you can see the zerk (grease nipple) and the hole which I drilled and tapped which will deliver grease to the volume around the shaft.
The bushings are a little loose, as I am still finding it difficult to get precision results with the boring bar - it seems to flex in varying amounts which depends on how much material I try to take off, making all of my cuts inconsistent. e.g. 60 thou movements take off about 60 thou, but 40 thou movements only take off about 25 thou. Need to talk to a machinist about this issue.
Friday, October 21, 2011
Front axle spindles; working with Dad
Working with Dad
Last weekend my Dad came up to help me do some planning on the ground; we laid out the steel I had and discussed some of the ideas I had for what I wanted to do.
I found that in designing it by myself I was tempted to consider too many things - since I'm a beginner at this scale of project I kept overwhelming myself with details so I found it really helpful to have a discussion with someone else who is mechanically inclined.
Just like the old days where I'd bond with Dad, each of us with a wrench in our hands :) He's going to be coming up every other weekend for a while so I expect progress to really pick up now! Love you Dad.
Buying additional steel
Initially I bought 20 feet of 1.5" square tube and 10 feet of 1.0" square tube, and some 1/4" plate for the motor mount. After talking with Dad and realizing how much steel this sucker is going to require, I have another 8 feet of 1.5" and 1.0" square, and 14 feet of 2" angle iron (for battery trays).
Probably 70 pounds of steel at this point, though since it's in a large pile it's hard to tell.
Front Spindles
To recap, my front tire assemblies are trailer tires connected to trailer stub axles (a bearing assembly with a 1 1/8" solid steel bar which will be welded to the spindle)
This spindle will be connected to a fork welded to the frame via a kingpin bolt - in my case, 5/8" dia. and 6" long.
It will look something like this. Of course to turn, the stub axle has to turn relative to the fork - it pivots on the kingpin. To provide easy rotation, I'm using two brass bushings for each spindle.
Thus the kingpin and fork remain stationary; the spindle holding the bushings rotates around the kingpin.
If you're wondering why the kingpin is at an angle, that angle is called the KPI (kingpin inclination). It should generally be set such that the kingpin points to the ground where the bottom of the tire is sitting. If this is not the case, it is difficult if not impossible to turn the tires!
Now I need a spindle that will hold the bushings, and is simple to weld to the stub axle. Of course no standard pipe sizes will fit the bushings 1" O.D., so I'll have to fabricate it myself.
What I saw on other go karts was always round spindle, because they use a different bearing assembly than I'm using (more purpose-made for go karts). Welding a round pipe to the round stub axle at this angle will require a lot of angle-grinding and even more patience. (Try and picture the intersection of these cylinders)
My friend Ron looked at me funny and asked why I didn't make square spindles - d'oh! The light came on, and I went to buy two 4" long sections of 1.5"x1.5" solid square bar. Of course this is after I spent $8 on 4" long sections of 1.5"x1.5" solid round bar. Sigh.
$10 for the pair. Cold rolled steel unfortunately - precision I don't need at a cost I'd rather not pay. Luckily the guy at the metal store cut me a break, should have been $20 but he knocked it down because he didn't have hot-rolled to sell me.
So here's the idea (without the angle)
To get the required angle, I will have to grind the stub axle so that it ends in an angle. Thankfully it now only requires a flat surface for the angle, which will be simple to accomplish compared to the complex curve of two intersecting cylinders. Huzzah!
Of course turning a square bar along its axis in a lathe is an interesting proposition for a novice. After a bunch of reading, I changed to a four-jawed chuck and spent several minutes with a dial indicator to manually adjust each jaw - getting the square bar centered within about 2 thou (0.002").
First I faced one side so the cut ends became square to the length of the bar. Turned it around, aligned it again, and faced the other side.
Next a center drill in the drill holder to get a perfect center for the hole. Followed by several very long and boring drilling operations - proceeding through 1/4", 9/32", 3/8", and 1/2" - drilling through the entire bar in each operation.
Here's what the result of about two hours of setting up and drilling looks like - you can see the circular lines around the hole which are the tool marks from 'facing' the bar to be flat.
Boy that's an awfully small hole - it's only 1/2" and it needs to be 1" to fit the bushing inside!
Now I have to bore the hole larger using a 'boring bar' on the carriage instead of in the drill chuck.
It's a single-tooth cutter that you push inside the hole, taking off at most 0.08" each time (at least 7 passes, each pass is 3 minutes at the feed speed I'm using - and that's only one side!)
Here's my poorly drawn explanation. It's rotated like 70° from what it should be (on that funny angle) but bear with me.
As you see the hole in the spindle does not need to be equally wide along its length!
Here's the first side machined to a hair over 1.00"; small enough that the bushing can't be pushed in by hand.
Perfect!
Note the kingpin doesn't go through since the hole on the other side is still only 1/2" in diameter, the boring bar is too short to do the entire spindle in one shot.
See where I'm going with this?
Now, repeat this process for the other side of the spindle.
Once you do, toss the bushings in the freezer (I happen to have access to one at -40°C) and push them in with an arbor press.
Unfortunately something happened with one of the bushings - it refuses to seat completely. You can see it sticking up here 3/16". However I've realized this could actually be beneficial.
Remember - this square spindle is held up by the wheel, while the fork is pushing down from the top. Thus the top fork will turn on the brass part, rather than scraping on the top of the spindle.
Of course this means what I did unintentionally with this side I must accurately replicate on the other.
Right - this is only one spindle of two I have to fabricate. Total time was probably 5 hours for this part, though I expect the second round will go much more quickly now that I know what I'm doing!
I'm pretty happy with how this spindle turned out, I think it will work well.
Final notes:
1. I realize the kingpings I have are too short for the spindles I made - there needs to be room for the fork on either end of the spindle, and two nuts to double-nut the kingpin and keep it from vibrating loose. This is good because I should have purchased a better grade of bolt (which I learned *after* I bought these bolts).
That's how it seems to go, buy, learn, buy again.
2. Grease fittings - you need to grease something like this. I have some zerk (grease) fittings that I plan on installing, one per spindle. It's a matter of drilling a hole into the side of the spindle, tapping it and threading the zerk in. The grease will stay in the area between the two bushings and keep everything lubricated in there.
Last weekend my Dad came up to help me do some planning on the ground; we laid out the steel I had and discussed some of the ideas I had for what I wanted to do.
I found that in designing it by myself I was tempted to consider too many things - since I'm a beginner at this scale of project I kept overwhelming myself with details so I found it really helpful to have a discussion with someone else who is mechanically inclined.
Just like the old days where I'd bond with Dad, each of us with a wrench in our hands :) He's going to be coming up every other weekend for a while so I expect progress to really pick up now! Love you Dad.
Buying additional steel
Initially I bought 20 feet of 1.5" square tube and 10 feet of 1.0" square tube, and some 1/4" plate for the motor mount. After talking with Dad and realizing how much steel this sucker is going to require, I have another 8 feet of 1.5" and 1.0" square, and 14 feet of 2" angle iron (for battery trays).
Probably 70 pounds of steel at this point, though since it's in a large pile it's hard to tell.
Front Spindles
To recap, my front tire assemblies are trailer tires connected to trailer stub axles (a bearing assembly with a 1 1/8" solid steel bar which will be welded to the spindle)
This spindle will be connected to a fork welded to the frame via a kingpin bolt - in my case, 5/8" dia. and 6" long.
Thus the kingpin and fork remain stationary; the spindle holding the bushings rotates around the kingpin.
If you're wondering why the kingpin is at an angle, that angle is called the KPI (kingpin inclination). It should generally be set such that the kingpin points to the ground where the bottom of the tire is sitting. If this is not the case, it is difficult if not impossible to turn the tires!
Now I need a spindle that will hold the bushings, and is simple to weld to the stub axle. Of course no standard pipe sizes will fit the bushings 1" O.D., so I'll have to fabricate it myself.
What I saw on other go karts was always round spindle, because they use a different bearing assembly than I'm using (more purpose-made for go karts). Welding a round pipe to the round stub axle at this angle will require a lot of angle-grinding and even more patience. (Try and picture the intersection of these cylinders)
My friend Ron looked at me funny and asked why I didn't make square spindles - d'oh! The light came on, and I went to buy two 4" long sections of 1.5"x1.5" solid square bar. Of course this is after I spent $8 on 4" long sections of 1.5"x1.5" solid round bar. Sigh.
So here's the idea (without the angle)
To get the required angle, I will have to grind the stub axle so that it ends in an angle. Thankfully it now only requires a flat surface for the angle, which will be simple to accomplish compared to the complex curve of two intersecting cylinders. Huzzah!
Of course turning a square bar along its axis in a lathe is an interesting proposition for a novice. After a bunch of reading, I changed to a four-jawed chuck and spent several minutes with a dial indicator to manually adjust each jaw - getting the square bar centered within about 2 thou (0.002").
First I faced one side so the cut ends became square to the length of the bar. Turned it around, aligned it again, and faced the other side.
Next a center drill in the drill holder to get a perfect center for the hole. Followed by several very long and boring drilling operations - proceeding through 1/4", 9/32", 3/8", and 1/2" - drilling through the entire bar in each operation.
Here's what the result of about two hours of setting up and drilling looks like - you can see the circular lines around the hole which are the tool marks from 'facing' the bar to be flat.
Boy that's an awfully small hole - it's only 1/2" and it needs to be 1" to fit the bushing inside!
Now I have to bore the hole larger using a 'boring bar' on the carriage instead of in the drill chuck.
It's a single-tooth cutter that you push inside the hole, taking off at most 0.08" each time (at least 7 passes, each pass is 3 minutes at the feed speed I'm using - and that's only one side!)
Not as early as I could have, but before I'd finished the boring operation, I realized that the hole through the spindle does not have to be 1" all the way through. In fact, it's best if the bushings sit in cutouts that are just deep enough to contain them, and between the two bushings the spindle is just slightly larger than the 5/8" kingpin. This way the bushings are not free to move about the spindle - it would cause serious problems if they moved.
- The blue area is the forks, and the connection to the go kart frame at the bottom of the image.
- The green area is the kingpin bolt, with head and nut at opposite ends of the fork holding everything together.
- The grey area with black boarder is the spindle I'm machining.
- The brown areas are the two bushings I'm machining the spindle to make room for.
As you see the hole in the spindle does not need to be equally wide along its length!
Perfect!
Note the kingpin doesn't go through since the hole on the other side is still only 1/2" in diameter, the boring bar is too short to do the entire spindle in one shot.
See where I'm going with this?
Now, repeat this process for the other side of the spindle.
Once you do, toss the bushings in the freezer (I happen to have access to one at -40°C) and push them in with an arbor press.
Remember - this square spindle is held up by the wheel, while the fork is pushing down from the top. Thus the top fork will turn on the brass part, rather than scraping on the top of the spindle.
Of course this means what I did unintentionally with this side I must accurately replicate on the other.
Right - this is only one spindle of two I have to fabricate. Total time was probably 5 hours for this part, though I expect the second round will go much more quickly now that I know what I'm doing!
I'm pretty happy with how this spindle turned out, I think it will work well.
Final notes:
1. I realize the kingpings I have are too short for the spindles I made - there needs to be room for the fork on either end of the spindle, and two nuts to double-nut the kingpin and keep it from vibrating loose. This is good because I should have purchased a better grade of bolt (which I learned *after* I bought these bolts).
That's how it seems to go, buy, learn, buy again.
2. Grease fittings - you need to grease something like this. I have some zerk (grease) fittings that I plan on installing, one per spindle. It's a matter of drilling a hole into the side of the spindle, tapping it and threading the zerk in. The grease will stay in the area between the two bushings and keep everything lubricated in there.
Thursday, September 22, 2011
Brakes - cleaning and bleeding; Blogger trouble
Today I've been trying to get my self back in the groove of working on the go-kart; it's been very long days at work for the past several weeks.
This post is quite long, and I apologize for the lack of pretty pictures. My hands were so black that there was no way I was holding a camera!
I decided to take another stab at bleeding the front brakes I got from my pal Chris.
They were in a motorcycle accident so they look a little worse for wear, and I've been having a really hard time trying to get the slave cylinders to move.
It's tricky holding the master cylinder and the brake line, then squeezing the handle to pump some brake fluid with only two hands. Fortunately I have access to a vice that rotates, so I turned the jaws so they face the floor, and used them to grab onto the top edges of the reservoir, thus holding it upright (so the fluid doesn't all run on the floor - you have to do this with the reservoir open!)
So, I held the hose with one hand and pumped with the other. Of course the fluid must go somewhere, so I held the open end of the brake line over the reservoir! At first, mostly air will come out.
Once fluid starts coming out regularly, I found the trick was to hold the banjo in the reservoir, so that the fluid was covering the hole in the banjo (the end of the brake line).
This way, when you release the brake handle, instead of sucking air back down the brake line it sucks fluid instead. Pump many (a dozen at least) more times to ensure the air is out of the master cylinder and lines. I found that when I fully depressed the handle I would still get a little air pumping out of the banjo. This happened over 100 times so I'm certain there wasn't really air in the system, though I can't quite convince myself where it is coming from.
Anyways, bolt the banjo back on the slave cylinder assembly (brake assembly? - whatever it's called, the part with the pads in it) and continue bleeding by carefully following these steps in order:
1. Hold slave such that bleed valve is the highest point (so air heads towards it, very important)
2. Open bleed valve
3. Cover bleed valve with a rag (to not make a mess when fluid jets out)
4. Fully depress handle of master cylinder
5. Tighten bleed valve
6. Release handle
7. Repeat steps 2 to 6 until only fluid comes out, no air at all.
8. Do it once more for good measure.
9. Refill your master cylinder!
I would also recommend doing this procedure with something (screwdriver, etc) in the jaws of the calipers - preferably the brake disk you will be using, though that may or may not be the easiest way.
I finally managed to feel some resistance on the handle once I finished bleeding, but the pistons wouldn't move! I pushed a little harder and I saw they were really just stuck with black grime and brake dust.
Pushing them out with the master cylinder and forcing them back in with a screwdriver (by slooowly but forcefully prying between the piston and the steel side of one brake pad, NOT between both pads or you will wreck the brake pads) you can eventually work them loose.
I decided I needed to take the brake assembly apart to really clean the pistons as they were still sticky after working them back and forth a few times. Taking them apart was a snap, undo one bolt and tap the two pins out; both brake pads fall out and you can clean the pistons freely.
However I noticed something odd inside the housing! My brake assembly has two pistons. A flat steel spring inside the housing pushes the brake pads up and out of the housing (against the two pins) - but it was not symmetrical!
The left piston had a perfectly flat side of the spring, while the right side was folded nearly in half.
I judged that the bending was not intentional, and hammered it (sort of) flat so that each side acted on the brake pads symmetrically.
I cleaned up everything I could get a rag on, especially the two pins, and thew it all back together.
The pads are much more free to slide along the pins now, opening and closing as the pistons move.
Before they were binding so hard to the pins that I could barely move them by prying with a screwdriver; now they can be forced around, I'm guessing it's good now.
Secondly, Blogger troubles -
Today when I tried to log in to write a post, it only gave me the option to Publicly or Privately follow my own blog, no editing options like usual, no homepage, etc. Logging out and in several times, trying different accounts to log in with (google, yahoo, etc) finally it opened normally.
Now I am following my own blog - and since I am successfully logged in, I have no option to stop following it!
Hilarious but more frustrating when you just want to make a post.
This post is quite long, and I apologize for the lack of pretty pictures. My hands were so black that there was no way I was holding a camera!
I decided to take another stab at bleeding the front brakes I got from my pal Chris.
They were in a motorcycle accident so they look a little worse for wear, and I've been having a really hard time trying to get the slave cylinders to move.
It's tricky holding the master cylinder and the brake line, then squeezing the handle to pump some brake fluid with only two hands. Fortunately I have access to a vice that rotates, so I turned the jaws so they face the floor, and used them to grab onto the top edges of the reservoir, thus holding it upright (so the fluid doesn't all run on the floor - you have to do this with the reservoir open!)
So, I held the hose with one hand and pumped with the other. Of course the fluid must go somewhere, so I held the open end of the brake line over the reservoir! At first, mostly air will come out.
Once fluid starts coming out regularly, I found the trick was to hold the banjo in the reservoir, so that the fluid was covering the hole in the banjo (the end of the brake line).
This way, when you release the brake handle, instead of sucking air back down the brake line it sucks fluid instead. Pump many (a dozen at least) more times to ensure the air is out of the master cylinder and lines. I found that when I fully depressed the handle I would still get a little air pumping out of the banjo. This happened over 100 times so I'm certain there wasn't really air in the system, though I can't quite convince myself where it is coming from.
Anyways, bolt the banjo back on the slave cylinder assembly (brake assembly? - whatever it's called, the part with the pads in it) and continue bleeding by carefully following these steps in order:
1. Hold slave such that bleed valve is the highest point (so air heads towards it, very important)
2. Open bleed valve
3. Cover bleed valve with a rag (to not make a mess when fluid jets out)
4. Fully depress handle of master cylinder
5. Tighten bleed valve
6. Release handle
7. Repeat steps 2 to 6 until only fluid comes out, no air at all.
8. Do it once more for good measure.
9. Refill your master cylinder!
I would also recommend doing this procedure with something (screwdriver, etc) in the jaws of the calipers - preferably the brake disk you will be using, though that may or may not be the easiest way.
I finally managed to feel some resistance on the handle once I finished bleeding, but the pistons wouldn't move! I pushed a little harder and I saw they were really just stuck with black grime and brake dust.
Pushing them out with the master cylinder and forcing them back in with a screwdriver (by slooowly but forcefully prying between the piston and the steel side of one brake pad, NOT between both pads or you will wreck the brake pads) you can eventually work them loose.
I decided I needed to take the brake assembly apart to really clean the pistons as they were still sticky after working them back and forth a few times. Taking them apart was a snap, undo one bolt and tap the two pins out; both brake pads fall out and you can clean the pistons freely.
However I noticed something odd inside the housing! My brake assembly has two pistons. A flat steel spring inside the housing pushes the brake pads up and out of the housing (against the two pins) - but it was not symmetrical!
The left piston had a perfectly flat side of the spring, while the right side was folded nearly in half.
I judged that the bending was not intentional, and hammered it (sort of) flat so that each side acted on the brake pads symmetrically.
I cleaned up everything I could get a rag on, especially the two pins, and thew it all back together.
The pads are much more free to slide along the pins now, opening and closing as the pistons move.
Before they were binding so hard to the pins that I could barely move them by prying with a screwdriver; now they can be forced around, I'm guessing it's good now.
Secondly, Blogger troubles -
Today when I tried to log in to write a post, it only gave me the option to Publicly or Privately follow my own blog, no editing options like usual, no homepage, etc. Logging out and in several times, trying different accounts to log in with (google, yahoo, etc) finally it opened normally.
Now I am following my own blog - and since I am successfully logged in, I have no option to stop following it!
Hilarious but more frustrating when you just want to make a post.
Sunday, July 10, 2011
Axle has arrived; upcoming plans
After a battle with a nasty 48 hour bug this week I managed to snap this photo of the new axle I bought from McMaster-Carr.
Axle
It is partially keyed - 14" on one side, 4" on the other. So, more then enough space for a wheel, drive sprocket and brake sprocket. It is made of 303 Stainless Steel - I'm darned happy because it is shiny, and it's going to stay that way. I would hate having a rusty steel axle and be fighting to remove all the sprockets from it in the future. The disadvantage is that the tensile strength is much lower, but still around 70,000lbs - It seems like a lot to me, but I'm sure the forces in this kind of system are intense.
For scale, the 1" bar in front is 12" long (30cm). The drive motor is properly aligned with the axle sprocket but perhaps too close together, I really need a frame to mock that up properly.
Frame
Speaking of frame, that's my task for this week, to go shopping at Metal Supermarkets, and to get a red flag or something to hang off the metal I'm sure will be sticking from the rear of my car. Thinking 1 1/2 square rather than 1 1/4 most (gas karts) use because of the extra weight I'll be lugging around in batteries.
Batteries
Still waiting for my contact at a certain battery company to get back to me. I have a contact who put me in touch with the sales manager, so I'm hoping to swing a great deal from them. It would cut a lot off the purchase price.
Interestingly I was also told to consider using NiMH - either industrial packs or sub-C cells - and making my own battery pack. Well that's the advantage of talking to people in the know, I would never have considered such a plan.
Apparently on Monster Garage they converted an old Bel Air to run on cordless drill batteries! Have to check that out some time.
Brakes
I've been reading a lot on www.diygokarts.com and a lot of people have been helpful there. A certain member who lives relatively close to me not only offered me advice and pictures of his experience, but also offered to sell me a set of working hydraulic brakes for a steal, only $60! Remember the bike shop earlier quoted $150 for the same exact deal - one set of used brake parts. Different models I am sure, but in both cases, just whatever was lying around.
I'm ecstatic! It might be a pain getting over to see him but totally worth it. I'm sure I will get a lot of sage advice too. Anyone else considering a similar project to this *really* needs to spend time on forums, there are some awesome people on the internet (i.e. in real life, that you can communicate with on the internet hehe)
Trailer
On a completely different note, I have been considering how to move this kart around when it's finished. Most people are settled and build these in their back yards... seeing as I am in an apartment this is a problem.
I have recently realized that my go kart has trailer tires, and the front (will have) actual trailer stub axles. So - get the kart licensed as a trailer, and tow it backwards! I'm thinking to build a pin into the steering mechanism to lock the steering straight for towing, and leaving a place to attach a long trailer hitch arm to the rear of the kart.
The Ontario website does not indicate much in the way of requirements for trailers so I think it should be relatively easy to get it plated.
Until next time...
Axle
It is partially keyed - 14" on one side, 4" on the other. So, more then enough space for a wheel, drive sprocket and brake sprocket. It is made of 303 Stainless Steel - I'm darned happy because it is shiny, and it's going to stay that way. I would hate having a rusty steel axle and be fighting to remove all the sprockets from it in the future. The disadvantage is that the tensile strength is much lower, but still around 70,000lbs - It seems like a lot to me, but I'm sure the forces in this kind of system are intense.
For scale, the 1" bar in front is 12" long (30cm). The drive motor is properly aligned with the axle sprocket but perhaps too close together, I really need a frame to mock that up properly.
Frame
Speaking of frame, that's my task for this week, to go shopping at Metal Supermarkets, and to get a red flag or something to hang off the metal I'm sure will be sticking from the rear of my car. Thinking 1 1/2 square rather than 1 1/4 most (gas karts) use because of the extra weight I'll be lugging around in batteries.
Batteries
Still waiting for my contact at a certain battery company to get back to me. I have a contact who put me in touch with the sales manager, so I'm hoping to swing a great deal from them. It would cut a lot off the purchase price.
Interestingly I was also told to consider using NiMH - either industrial packs or sub-C cells - and making my own battery pack. Well that's the advantage of talking to people in the know, I would never have considered such a plan.
Apparently on Monster Garage they converted an old Bel Air to run on cordless drill batteries! Have to check that out some time.
Brakes
I've been reading a lot on www.diygokarts.com and a lot of people have been helpful there. A certain member who lives relatively close to me not only offered me advice and pictures of his experience, but also offered to sell me a set of working hydraulic brakes for a steal, only $60! Remember the bike shop earlier quoted $150 for the same exact deal - one set of used brake parts. Different models I am sure, but in both cases, just whatever was lying around.
I'm ecstatic! It might be a pain getting over to see him but totally worth it. I'm sure I will get a lot of sage advice too. Anyone else considering a similar project to this *really* needs to spend time on forums, there are some awesome people on the internet (i.e. in real life, that you can communicate with on the internet hehe)
Trailer
On a completely different note, I have been considering how to move this kart around when it's finished. Most people are settled and build these in their back yards... seeing as I am in an apartment this is a problem.
I have recently realized that my go kart has trailer tires, and the front (will have) actual trailer stub axles. So - get the kart licensed as a trailer, and tow it backwards! I'm thinking to build a pin into the steering mechanism to lock the steering straight for towing, and leaving a place to attach a long trailer hitch arm to the rear of the kart.
The Ontario website does not indicate much in the way of requirements for trailers so I think it should be relatively easy to get it plated.
Until next time...
Sunday, July 3, 2011
Princess Auto shopping trip
This weekend I spent three hours (and several hundred dollars, sigh) on a bunch of mechanical parts for the project, and a little in the way of tools.
I ended up buying the tires that were on sale, they are Carlisle trailer tires, 16.5 inches diameter. Unfortunately they only had 3 in store, so I got a rain check and will have to go back to get the fourth.
I chose #50 chain and a 1" rear axle. Here are the rear sprocket and the motor sprocket, chosen for a gear ratio of about 2.5. I ended up with 48 and 18 teeth, for an actual ratio of 2.66.
All the sprockets I used are designed to be welded onto the hubs which are keyed to attach to the axle.
So here is the first real welding I have done in a few years, for the rim attachments.
It is fairly ugly, and was hard to take a picture of. A wire brushing would have helped, but I did bang off the slag with my welding hammer. The second hub went much better than the first, but still needs a some more improvement.
I then expanded the holes with 3/8 and 7/16 drills. The bolts I am using were designed for tire applications, to be hammered into the hub. Of course the dimensions are not handy; the threaded section is 1/2" but the flat area is 0.53" and the ridged area which provides the holding effort is about 0.55".
I had to use the mill here again to get the dimensions right; I don't know exactly how big the hole was but just over 0.53".
See the ridges don't quite fit? This is perfect. Now you have to beat the shit out of the bold head to drive it into this sprocket, which I swear is hardened steel. It was very difficult - if I made the holes larger it would have been easier, but there would have been less grip strength in rotation.
Hey, it fits!
Here's the bolt side.
You can't tell but the ridged area is too wide, so the nuts don't completely seat. I need to add spacers for a better fit. I should have used thicker sprockets instead.
Both sprockets together
Here's the posi-lube stub axle which I will be using for the front axles.
Both tires bolted to hubs and on the scrap 1" bar again.
Next I have to buy a 1" keyed axle, some keystock, locking collars, and a bunch of metal from Metal Supermarket.
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