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Matt’s Off-road Recovery Starting a Bombi Tub Build
- Thread starter Mill666er
- Start date
J5 Bombardier
Well-known member
They yanked the controlled diff and went with a truck axle with disc brakes . It will be interesting to see how the new steering holds up during an extended test drive .
J5Bombardier
J5Bombardier
Every homemade snow cat that I've seen with that style brake steer does not work. A controlled differential with brakes is completely different than what they are trying to achieve. Not saying it's not going to work, but I've been watching also. I imagine there's going to be some glowing red metal in a tite and twisty trail.
Snowy Rivers
Well-known member
MY TAKE ON THIS
If a regular truck diify with disc brakes would work good.. (Or even mediocre) the cat mfg would never have used the planetary type units such as the C4, OC-12 and similar style boxes.
This setup will not be a great success....GLOWING BRAKES DISCS....YESSSSSSSSS
But...it is their project and that's the bottom line......I do see a "Change order" down the line....And it will be costly....
If a regular truck diify with disc brakes would work good.. (Or even mediocre) the cat mfg would never have used the planetary type units such as the C4, OC-12 and similar style boxes.
This setup will not be a great success....GLOWING BRAKES DISCS....YESSSSSSSSS
But...it is their project and that's the bottom line......I do see a "Change order" down the line....And it will be costly....
Snowy Rivers
Well-known member
Many folks will dump in 85/140 rear axle lube...
Works fine with Ring and pinion as well as the bearings....The steering bands just do not like that type of oil....
The bands do not grab the drums well at all....
We used to have an Oliver Crawler here at the ranch.....50 weight mineral oil was what Oliver spec'd out....
Milk shake....water got in the box.....
Works fine with Ring and pinion as well as the bearings....The steering bands just do not like that type of oil....
The bands do not grab the drums well at all....
We used to have an Oliver Crawler here at the ranch.....50 weight mineral oil was what Oliver spec'd out....
Milk shake....water got in the box.....
that rig appears to be a br100 with a custom cab.
bombis are really light for towing work in my opinion.
He is aware its a bombi. im impressed he doesnt bust it up more than it does.
i just binge watched it.... our own danny gates is in the second video. great thiokol guy to have as a consultant
bombis are really light for towing work in my opinion.
He is aware its a bombi. im impressed he doesnt bust it up more than it does.
i just binge watched it.... our own danny gates is in the second video. great thiokol guy to have as a consultant
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Snowy Rivers
Well-known member
I was thinking about the steering that Matt is planning on......
One way that this could work pretty well would be to use a brake caliper designed to run hydraulic oil instead of brake fluid.
Then set up an aggressive control system similar to that used on the 2100 Thiokol.
Basically full pressure off of a hydraulic pump (Controlled pressure) that will lock the brake disc quickly.
Steering with the manual master cylinders.....???? Not gonna happen......
The OC-12 used in the 2100 has 400 psi off the main hydraulic system delivered to the steering brakes via the control levers.
The pressure is OFF....ON No feathering or light application.
Even with this system the bands in the OC-12 needed to be serviced often (Seasonally or sooner)
The 2100 is an 8000# machine with a 14 foot blade....57" tracks and the high profile "J" grousers ....This combination works the hell out of the bands....Especially when the machine is grooming.....
The same OC-12 in a Spryte with 36" tracks can function quite well with the manual controls run with master cylinders and hand levers.....
If Matt uses very aggressive brake pads and operates them with hydraulics it will probably work.....Given the lighter weight of the Bombi......
Big issue is to reduce the amount of brake slip and resultant heat.
Hard chromed rotors with air vents and very extreme pads....
The machine is going to be a very jerky steering beast.....
The OC-12 (Or similar) shifts one track to a 1/3 lower speed and the other to 1/3 higher and keeps power to both tracks all the time during a turn....
Small "Jabs" on the controls will make subtle steering corrections (Sort of like a froggy)
It will be interesting to see how the Bombi works after the refit....
The one issue with using the truck diffy is that the track has to be slowed down or stopped.....This takes a tremendous amount of power (HEAT) to accomplish....
Another way would be to rework the diffy .....(Diffy would need a spool) Add a multi plate clutch on each side of the axle to uncouple each axle separately and then apply the disc brake ......
This would be more like the old Caterpillar type steering.
For small steering corrections releasing the clutches and freeing up the track would allow some easy maneuvers ....Apply the brake and then things would really come around.
The one caveat is....LOCKING THE TRACK COULD CAUSE ISSUES..
Ah well.....WE will have a ringside seat to see what happens....
One way that this could work pretty well would be to use a brake caliper designed to run hydraulic oil instead of brake fluid.
Then set up an aggressive control system similar to that used on the 2100 Thiokol.
Basically full pressure off of a hydraulic pump (Controlled pressure) that will lock the brake disc quickly.
Steering with the manual master cylinders.....???? Not gonna happen......
The OC-12 used in the 2100 has 400 psi off the main hydraulic system delivered to the steering brakes via the control levers.
The pressure is OFF....ON No feathering or light application.
Even with this system the bands in the OC-12 needed to be serviced often (Seasonally or sooner)
The 2100 is an 8000# machine with a 14 foot blade....57" tracks and the high profile "J" grousers ....This combination works the hell out of the bands....Especially when the machine is grooming.....
The same OC-12 in a Spryte with 36" tracks can function quite well with the manual controls run with master cylinders and hand levers.....
If Matt uses very aggressive brake pads and operates them with hydraulics it will probably work.....Given the lighter weight of the Bombi......
Big issue is to reduce the amount of brake slip and resultant heat.
Hard chromed rotors with air vents and very extreme pads....
The machine is going to be a very jerky steering beast.....
The OC-12 (Or similar) shifts one track to a 1/3 lower speed and the other to 1/3 higher and keeps power to both tracks all the time during a turn....
Small "Jabs" on the controls will make subtle steering corrections (Sort of like a froggy)
It will be interesting to see how the Bombi works after the refit....
The one issue with using the truck diffy is that the track has to be slowed down or stopped.....This takes a tremendous amount of power (HEAT) to accomplish....
Another way would be to rework the diffy .....(Diffy would need a spool) Add a multi plate clutch on each side of the axle to uncouple each axle separately and then apply the disc brake ......
This would be more like the old Caterpillar type steering.
For small steering corrections releasing the clutches and freeing up the track would allow some easy maneuvers ....Apply the brake and then things would really come around.
The one caveat is....LOCKING THE TRACK COULD CAUSE ISSUES..
Ah well.....WE will have a ringside seat to see what happens....
Snowy Rivers
Well-known member
The Frandee is outside of my purview .....There have been many things tried over the years...so It would not surprise me..
I watched some of Matts video on the Bombi build.....
Why did they scrap the original diffy ???? anyone hear that part...????
I watched some of Matts video on the Bombi build.....
Why did they scrap the original diffy ???? anyone hear that part...????
had what looked like water emulsified gear lube. he states it didnt turn.
frandee early on had front and rear diffs.
Snowy Rivers
Well-known member
Yeah....MILKSHAKE ..
DOES NOT TURN
Yup....been there done that trip......My 2100 was pretty much that sort of mess....
Complete tear down....replace all the bearings....Reline the bands....
Took a 6 foot cheater on the 3/4" breaker bar to get this bad boy to turn.
A lot of cleaning and fooling with crud...
Actually was a lot better than I would have ever believed possible.....
Opening the top for the first time left a sick feeling in the pit of my gut....
Unless gears are broken these can be brought back from the valley of the shadow of death pretty easy....
DOES NOT TURN
Yup....been there done that trip......My 2100 was pretty much that sort of mess....
Complete tear down....replace all the bearings....Reline the bands....
Took a 6 foot cheater on the 3/4" breaker bar to get this bad boy to turn.
A lot of cleaning and fooling with crud...
Actually was a lot better than I would have ever believed possible.....
Opening the top for the first time left a sick feeling in the pit of my gut....
Unless gears are broken these can be brought back from the valley of the shadow of death pretty easy....
Attachments
Snowy Rivers
Well-known member
Just a FWIW.
The big roller bearing right in front of the head of the pinion (img 2306) can be seen in the case.
After getting the bearings out and logging the ###### I started shopping.
Local supply house wanted $700 and change for that bad boy..
I crapped my pants.....
Hit ebay....found a NOS in a very ratty looking box...$20 to my door....Box was just trash...Bearing was in a sealed plastic wrap...
Box marked 1986 IIRC......
Ebay shopped all the bearings....
14 big bearings in an OC-12..
PINION (2)
CARRIER(2)
DROP BOXES (8) 4 EACH BOX
OUTER AXLE (2) 1 EACH
THE SAVINGS BY GOING WITH NOS WAS OFF THE CHARTS
One bearing came from Slovinia....Took about a month to get here.
The drop box bearings....I got a roll of those....I think there were 10 in the roll...
The big bearing by the pinion gear is a big azz roller.....High load carrying ability
The outer pinion bearing behind the input is a large radial ball bearing.....
I still would like to know why Matt did not rebuild the steering box in the Bombi.....??????
Basically the same as the OC-12....Just a bit smaller
These boxes are a breeze to repair.....Mark everything....Rip it apart...Order the bearings and seals....stuff it back together...
I had to make a few tools to hold stuff and a wrench to tighten the carrier retaining nuts.....
I machined the internals of the compensator to allow using real tranny thrust bearings instead of the thin steel shim washers....(These wear and break...then the chunks go through the bearings and gears and break stuff)
Adding the much stouter thrust washers...."The Cats AZZ" Designed to handle thrust....Shim steel wears out ....JUNK
Deburing all the compensators....Gotta do it...
A bit of time figuring out what washers would work...TH400 rear washer on each drum
Ford A4OD washer in the compensator.....
These mods will allow the parts to work and not chew itself up...
The big roller bearing right in front of the head of the pinion (img 2306) can be seen in the case.
After getting the bearings out and logging the ###### I started shopping.
Local supply house wanted $700 and change for that bad boy..
I crapped my pants.....
Hit ebay....found a NOS in a very ratty looking box...$20 to my door....Box was just trash...Bearing was in a sealed plastic wrap...
Box marked 1986 IIRC......
Ebay shopped all the bearings....
14 big bearings in an OC-12..
PINION (2)
CARRIER(2)
DROP BOXES (8) 4 EACH BOX
OUTER AXLE (2) 1 EACH
THE SAVINGS BY GOING WITH NOS WAS OFF THE CHARTS
One bearing came from Slovinia....Took about a month to get here.
The drop box bearings....I got a roll of those....I think there were 10 in the roll...
The big bearing by the pinion gear is a big azz roller.....High load carrying ability
The outer pinion bearing behind the input is a large radial ball bearing.....
I still would like to know why Matt did not rebuild the steering box in the Bombi.....??????
Basically the same as the OC-12....Just a bit smaller
These boxes are a breeze to repair.....Mark everything....Rip it apart...Order the bearings and seals....stuff it back together...
I had to make a few tools to hold stuff and a wrench to tighten the carrier retaining nuts.....
I machined the internals of the compensator to allow using real tranny thrust bearings instead of the thin steel shim washers....(These wear and break...then the chunks go through the bearings and gears and break stuff)
Adding the much stouter thrust washers...."The Cats AZZ" Designed to handle thrust....Shim steel wears out ....JUNK
Deburing all the compensators....Gotta do it...
A bit of time figuring out what washers would work...TH400 rear washer on each drum
Ford A4OD washer in the compensator.....
These mods will allow the parts to work and not chew itself up...
Attachments
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chowderman
Well-known member
a lot of the elderly machinery was designed around inch dimension bearings - which are, today, rare and getting rarer - the bearing world has gone metric.
I'd look at machining / sleeving to a standard metric size - it'll be necessary, now or later . . .
I'd look at machining / sleeving to a standard metric size - it'll be necessary, now or later . . .
Snowy Rivers
Well-known member
The OC-12 is all metric bearings....
A complete list of bearings in the OC-12
Getting all the numbers off of the rusty mess in that box was a job...
Some bearings had only etchings and not real deep type numbers..
But the PDF page has all the numbers used for the bearings and seals.....
The original drop box bearings were sealed where the top bearing goes into the drop box....This kept the oil separate.
My box had open bearings in top and bottom of the drops....So I replaced with same.....
It just allows the oil from the main box to flow through everything...including the axle tubes....
I have double sealed bearings for the axle bearing to help keep things dry....
Early diffy's had a seal to keep the diffy oil from reaching the outer axle bearing....
These also used a snap ring to retain the bearing....Bad JU JU....The axles would snap at the ring groove...
Stress riser.....Newer axles used a press on collar to hold the bearing....Like a 9" Ford does...
My axle uses the pressed on rings (Wedding bands)
Main thing is to be sure the axle tubes are full of oil and the drop boxes too......
Air vent must be allowed to vent to atmosphere above the top of the diify with a loop to stop blow over...
The top cover has a small hole in the plate with a sintered vent that the hose connects to.....
As long as the diffy and drops are to the level of the FULL HOLE ON THE DIFFY....Good to go...
A complete list of bearings in the OC-12
Getting all the numbers off of the rusty mess in that box was a job...
Some bearings had only etchings and not real deep type numbers..
But the PDF page has all the numbers used for the bearings and seals.....
The original drop box bearings were sealed where the top bearing goes into the drop box....This kept the oil separate.
My box had open bearings in top and bottom of the drops....So I replaced with same.....
It just allows the oil from the main box to flow through everything...including the axle tubes....
I have double sealed bearings for the axle bearing to help keep things dry....
Early diffy's had a seal to keep the diffy oil from reaching the outer axle bearing....
These also used a snap ring to retain the bearing....Bad JU JU....The axles would snap at the ring groove...
Stress riser.....Newer axles used a press on collar to hold the bearing....Like a 9" Ford does...
My axle uses the pressed on rings (Wedding bands)
Main thing is to be sure the axle tubes are full of oil and the drop boxes too......
Air vent must be allowed to vent to atmosphere above the top of the diify with a loop to stop blow over...
The top cover has a small hole in the plate with a sintered vent that the hose connects to.....
As long as the diffy and drops are to the level of the FULL HOLE ON THE DIFFY....Good to go...
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Well the first video is out. And it did not disappoint. Us at least. I think Matt was a little disappointed in his turning ability.
tommu56
Bronze Member
Not that I've ever driven a snow cat but if stock rears would work the dozers I've driven would have been using them instead of clutches on each track side.
Bennyboy1337
Active member
It seems odd the rear tires (which also have breaks) are just sliding when he steers. This means the front disks are doing 100% of the work, and no wonder they're burning out so fast. Maybe just a wider tire in the rear will grip the tracks better and mostly solve the problem? But yeah... no matter what he does it will never bee good as the original OC12 for steering. I think with some tweaking he can get his design to work, we know it's possible because of cats like the Frandee. He mentioned possibly doing hydro drive which would be a horrible idea and negate the whole point of having an LS on that machine, might as well swap in a little 4 cylcinder Kabota if you're going that route.
luvthemvws
Active member
I think his combination of Brake Lever length, Master Cylinder bore diameter and Caliper Piston diameter is off. He cannot build enough fluid pressure to get a hard grip on the rotor to adequately stop the chosen track. I hope Matt gets it sorted out soon. I love the Bombi recoveries!
MontanaTweak
Member
His bombi steering difficulties are interesting considering so many Russians and DonnyDIY have made successful ground up tracked vehicle builds with the same concept and they seem to work fine. Granted, these Russian DIY builds are lighter horsepower vehicles, but they appear to work great. Is it because Matt is running a higher HP motor?
When you hand turn a truck axle you can divert power to the other wheel with hand pressure alone. So why is Matt's problematic? Trying to wrap my head around the physics of it?
DonnyDIY auto diff/brake steer
When you hand turn a truck axle you can divert power to the other wheel with hand pressure alone. So why is Matt's problematic? Trying to wrap my head around the physics of it?
DonnyDIY auto diff/brake steer
what most people can't grasp, is the open differential is a one to one deal.
stop one wheel and the other becomes Over driven.
Planetary differentials (which he put on a skid out side) merely under drives the braked side and the perceived over speed to the other side,turns the rig. ( Like two three speed transmissions )
Matts system removes the drive torque and puts that energy in the brakes as heat. the other side then has no choice but to run the torque across a center pin to the other track, while needing to overspeed or shear the cross pin.
It pains me to see him struggle as he has some really smart people involved in the build
stop one wheel and the other becomes Over driven.
Planetary differentials (which he put on a skid out side) merely under drives the braked side and the perceived over speed to the other side,turns the rig. ( Like two three speed transmissions )
Matts system removes the drive torque and puts that energy in the brakes as heat. the other side then has no choice but to run the torque across a center pin to the other track, while needing to overspeed or shear the cross pin.
It pains me to see him struggle as he has some really smart people involved in the build
MontanaTweak
Member
So something like an OC-12 isn’t an “all or nothing” differential like a standard automotive open diff essentially.
Lotta small engine automotive open differentials being used on hack Russian rigs.
Lotta small engine automotive open differentials being used on hack Russian rigs.
any thing like a OC 4, 12 , 15 ect is basically a sun gear or planetary setup. Planetary if you would like is basically two three speeds side by side. I got a good look at the ripsaw or whatever the howe and howe product is called. it uses a clutched braked differential like a early thiokol. they have a processor that modulates the brake and clutch to give a controlled feel. Lexus does it in their sports cars. But you hit it on the head with the weight.
Want to get some work done the machines that can do some work tend to be a bit heavy.
I have snapped lots of cross pins in dana 44,60,70 rear diffs. ( mud dragging, truck pulling, mountain climbing ect )
here is a crappy video I shot last week.
it is of a early thiokol declutching and then braking the right track, You get to see the dash while I am turning, but keep watching to see what a open diff like matts does When you brake one side. great for moving people and other snow cat fun, but.........
Want to get some work done the machines that can do some work tend to be a bit heavy.
I have snapped lots of cross pins in dana 44,60,70 rear diffs. ( mud dragging, truck pulling, mountain climbing ect )
here is a crappy video I shot last week.
it is of a early thiokol declutching and then braking the right track, You get to see the dash while I am turning, but keep watching to see what a open diff like matts does When you brake one side. great for moving people and other snow cat fun, but.........