Project Update 03-28-04
Goodies in the mail!
Got this stuff in the mail from surpluscenter.com. With these and other recently procured goodies, I started working on the wooden chassis mockup.
Wooden Mockup Construction
If you want to save some time I suggest you just watch the vids. They pretty much cover everything here plus some more.
http://www.cp-tel.net/pasqualy/land...es/DTtest01.wmv ~7 megs
http://www.cp-tel.net/pasqualy/land...es/DTtest02.wmv ~4 megs
First off I had to do a ton of work on the wheels, spindles, rims, and hubs. The original hubs were designed to spin on the shaft. Im my case they needed to locked to the shaft. To do this, I drilled a hole though the hub and shaft and pinned it with a bolt.
Now that I had done this, the rims had to be modified so that the hubs would fit though with the bolt. Trying to stick the bolt in once the hub was in its socket was just out o f the question. This was a huge pain in the rear.
Here you can see the beginning stages of the body and spindles. Getting all this stuff to line up was pretty hard but I'm pretty satisfied with the way the work came out. I had to do very little adjusting.
Here you can get an idea of how things are gonna work with the motors and chain.
I mounted down the motors between wooden blocks to keep them from shifting.
This white bar you see is PVC pipe slipped over a 1/2in rod. It was supposed to provide chain tension but it didn't work so well.
One side ate into the PVC and the other side was a little too slack.
You can see how the chain winds its way between the sprockets etc. It goes over the motor sprocket and then under the PVC tension bar. I found out later that this doesnt make it bite nearly enough teeth for what I'm doing. But more on that later.
Here are some pics of the final deal. I aired up the tires and found I had two flats. I patched one and had to purchase a tube for another.
Here is a good view of how things are working in there.
Here are two pics to help you understand the size of this thing. Its freeking huge!!!
Remember, those are 14 inch tires!
I placed some of the other possible devices on the top deck just to get an idea of how much space I had. I realized that I just didn't have room for everything. So I decided to build a second deck. That would come later though. Looks pretty neat with all these goodies on it!
Here is the aftermath in my store. No worries though, it cleaned up ok. :)
Problems Problems...
When it was all said and done it worked pretty well but for two major problems.
1. Chain popping.
The chain just wasn't gripping enough on the motor sprockets and the tension bar sucked. This will definetly have to have a major change done to it.
2. Skid turning requires lots of torque!
When you think about it, it makes sense, skid steering requires that your tires move off center to the direction that they want to turn. Rolling a wheel is easy. Pushing one sideways is not. The wider the wheelbase (left to right) the easier the turn because there off angle of movement is smaller. The Shorter the wheelbase (front to back) the easier the turn as well. I have about 5 inches or so in between wheel edges (front to back) that I can lose to help reduce torque needs but this won't be enough.
I can't go any wider either, she is just slim enough to fit though a doorway. So I have to add more power and also probably gear down the drive train.
If you want to know more about the problems of skid steering click here.
We also decided to try out only having a two wheel drive and caster setup. However this looked really lame and wasn't nearly as strong offroad as the 4wheel skid steering design was. Also it was really hard to drive this way so we gave up on that idea pretty quick. More on that and other solutions in the next update.
Here are the videos.
They Actually go into better detail than this page does and they include video of the caster test etc.
http://www.cp-tel.net/pasqualy/land...es/DTtest01.wmv ~7 megs
http://www.cp-tel.net/pasqualy/land...es/DTtest02.wmv ~4 megs
Got this stuff in the mail from surpluscenter.com. With these and other recently procured goodies, I started working on the wooden chassis mockup.
Wooden Mockup Construction
If you want to save some time I suggest you just watch the vids. They pretty much cover everything here plus some more.
http://www.cp-tel.net/pasqualy/land...es/DTtest01.wmv ~7 megs
http://www.cp-tel.net/pasqualy/land...es/DTtest02.wmv ~4 megs
First off I had to do a ton of work on the wheels, spindles, rims, and hubs. The original hubs were designed to spin on the shaft. Im my case they needed to locked to the shaft. To do this, I drilled a hole though the hub and shaft and pinned it with a bolt.
Now that I had done this, the rims had to be modified so that the hubs would fit though with the bolt. Trying to stick the bolt in once the hub was in its socket was just out o f the question. This was a huge pain in the rear.
Here you can see the beginning stages of the body and spindles. Getting all this stuff to line up was pretty hard but I'm pretty satisfied with the way the work came out. I had to do very little adjusting.
Here you can get an idea of how things are gonna work with the motors and chain.
I mounted down the motors between wooden blocks to keep them from shifting.
This white bar you see is PVC pipe slipped over a 1/2in rod. It was supposed to provide chain tension but it didn't work so well.
One side ate into the PVC and the other side was a little too slack.
You can see how the chain winds its way between the sprockets etc. It goes over the motor sprocket and then under the PVC tension bar. I found out later that this doesnt make it bite nearly enough teeth for what I'm doing. But more on that later.
Here are some pics of the final deal. I aired up the tires and found I had two flats. I patched one and had to purchase a tube for another.
Here is a good view of how things are working in there.
Here are two pics to help you understand the size of this thing. Its freeking huge!!!
Remember, those are 14 inch tires!
I placed some of the other possible devices on the top deck just to get an idea of how much space I had. I realized that I just didn't have room for everything. So I decided to build a second deck. That would come later though. Looks pretty neat with all these goodies on it!
Here is the aftermath in my store. No worries though, it cleaned up ok. :)
Problems Problems...
When it was all said and done it worked pretty well but for two major problems.
1. Chain popping.
The chain just wasn't gripping enough on the motor sprockets and the tension bar sucked. This will definetly have to have a major change done to it.
2. Skid turning requires lots of torque!
When you think about it, it makes sense, skid steering requires that your tires move off center to the direction that they want to turn. Rolling a wheel is easy. Pushing one sideways is not. The wider the wheelbase (left to right) the easier the turn because there off angle of movement is smaller. The Shorter the wheelbase (front to back) the easier the turn as well. I have about 5 inches or so in between wheel edges (front to back) that I can lose to help reduce torque needs but this won't be enough.
I can't go any wider either, she is just slim enough to fit though a doorway. So I have to add more power and also probably gear down the drive train.
If you want to know more about the problems of skid steering click here.
We also decided to try out only having a two wheel drive and caster setup. However this looked really lame and wasn't nearly as strong offroad as the 4wheel skid steering design was. Also it was really hard to drive this way so we gave up on that idea pretty quick. More on that and other solutions in the next update.
Here are the videos.
They Actually go into better detail than this page does and they include video of the caster test etc.
http://www.cp-tel.net/pasqualy/land...es/DTtest01.wmv ~7 megs
http://www.cp-tel.net/pasqualy/land...es/DTtest02.wmv ~4 megs
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