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Brake assistance needed

Garauld

New member
Hi gang - I am a retired mech. engineer with a affinity for downhill skiing. I was getting bored working on stuff around the house so I decided I needed a new project to keep from going bonkers. Why not build a snowcat? I embarked on this project and have reached a point where my machine (called Snowzer) is actually able to move about. If you want to see some of the build history, you can check it out here: http://www.tractorbynet.com/forums/...-senior-design-project-swamp.html#post5112906

Here's a recent image of it:
JTisyhb.jpg



The problem I am having is the steering brakes are very weak - it takes a lot of effort to get it to turn. I believe it may be part of my current design as I do not use vacuum boosters to help. Here is a photo of the brake system. The red calipers are the service brakes and the blue ones are for steering. You can see the steering master cylinders at the top of the image. Maybe I should use hydraulic boosters? Any suggestions on how to improve the brakes would be most appreciated. Thanks!


ZfnAfzC.jpg
 

Snowcat Pat

Active member
Grass is like Velcro. No two track will turn easily on grass, I built a cat using a truck diff and had the same problem. Get it on snow you will notice a big difference. It will turn easier when you lock one track fully to turn as the machine will pivot around the locked side grousers like ice skates, sort of. On mine the brakes overheated constantly even though they ran in snow, and wore out pads every 30 miles or so. Performance was inconsistent to say the least. Replaced the diff with M-29 Weasel and problem solved, except on grass.

-Pat
 

luvthemvws

Active member
I love it!
Try putting a hydraulic pressure gauge (temporarily) in the steering brake caliper circuit. With "reasonable" brake lever force you need to attain 600-800 psi. Use a smaller bore master cylinder and/or a longer lever to get the pressure. To make a hard/firm stop you need to generate about 1000 psi. I prefer doing this with longer levers or smaller m/c bores rather than vacuum boosters (the KISS principle ).
I am probably not telling anything new to an engineer such as yourself, but just pointing out what has served me well in my oddball projects.
I look forward to seeing you out on the trails!
 

Snowtrac Nome

member formerly known as dds
GOLD Site Supporter
I would ditch the open dif and get a controlled differential like a bombi or m29 weasel you will find it preforms better in soft snow that way as you will maintain power to both tracks when turning. the build looks real nice other wise get your steering straight you will have a nice rig. As pat said grass is a grapy place to test it my light foot is 25 miles off the road with a torn track right now from trying to steer in dry tundra.
 

Snowy Rivers

Well-known member
Very interesting rig.

I agree with Pat.

Cats like the Thiokol used a planetary diffy and the system shifts one track or the other into 1/3 lower gear ratio.

Trying to lock up one brake or the other in a standard diffy takes serious force to accomplish.

Snoop around and scare up an M29 Weasel rear axle.....

Good looking little unit.....

Gonna be great fun.....
 

Garauld

New member
Thanks for the feedback. :smile: I will pursue working with the open diff option for a while as it gives me something to tinker with. Changing master cylinders is relatively easy compared to changing out the whole front drive system.
 
Other than hydrostatics, the best steering system I had was an old John Deere 440IC dozer. It had a set of multi-disc clutches that were between the diff and axels and then a set of drum brakes on the axels. When you pulled on the lever a certain distance the clutch on that side would disengage and if you pulled back further the brake would engage and the track would lock up. Best turning two track in dirt and snow.
 

Snowtrac Nome

member formerly known as dds
GOLD Site Supporter
your right Randy the down side of clutch brake is the removal of power from one track. it actually works well with smaller equipment like my little john deere 350 dozer on some of the larger dozers like a d-8 k truing to steer with a load of dirt infront of the blade will result in a bull gear missing teeth. for that little rig adding a set of dry clutches like a raid track has to the existing brake system would be ideal.
 

Snowy Rivers

Well-known member
I agree with Snowtrac on the clutch idea.

Being able to cut one side loose and then apply the brakes would be sweet..

At speed just cutting the drive feed to that track will give the ability to make gentle turns and the applying the brakes at varying degrees will allow the turning ability to be greatly increased.

Trying to force a standard differential to operate takes a lot of power (Brake force)

The only downside to the clutch/brake system is as mentioned....when you uncouple one side the power to the ground is lost......

In order for this to work with the open differential though will require replacing the diffy center section with a spool.

As it is when the clutch is released the spider gears will allow all the power to go out the open side and all power to the tracks will be lost...
 

Tetonka

New member
Hi. I know your post about brake ideas was 9 months ago but I’ll add my 2 cents still.
Mine operates with a standard dif brake steer. I have boosters on both left and right side master cylinders but it was always an arm workout to steer. I tried and contemplated many ways to improve steering. I now installed electric actuators that move the original manual joy sticks. I built a small drop down arm that has two small thumb joy sticks that move the actuators in and out. It’s effortless now and I have 900 lbs pressure from them so more than I could pull with my arms in old system. It was tight to fabricate the linkage for them under the dash but well worth all the work.
 
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