• Please be sure to read the rules and adhere to them. Some banned members have complained that they are not spammers. But they spammed us. Some even tried to redirect our members to other forums. Duh. Be smart. Read the rules and adhere to them and we will all get along just fine. Cheers. :beer: Link to the rules: https://www.forumsforums.com/threads/forum-rules-info.2974/

SV-252 won't drive straight

U

undy

New member
My Bombardier SV-252 doesn't follow a straight path, it veers gradually left. So to follow a straight course, I must lightly apply the right brake almost continually. I'm fairly sure the tracks are properly tensioned.

Any ideas what might be causing this?

Thanks in advance for any input.
 
no offence but bombies seem to do the same, aside from a band dragging. I think it is the nature of the beast on those bombardier products. I have a buddy with a 601 that does the same he just sets up for a wide arc and runs in a lazy s, on long straight trips. the 2100 seems to run pretty straight almost as good as a snow trac
 
Hmmm. I hope it isn't the nature of this beast. It doesn't seem to make too much difference for me grooming, but out just going somewhere, it's annoying.

I'll maybe have to get it off the ground, and try to check the items JimVT mentioned.

Thanks for those thoughts.
 
I would look at them my experience with ski dozers are limited but I have had a lot of bombie experience. I think there wander is a combination of short tracks and front drive, both of which yours doesn't have. the one thing I noticed about the bombi that blew out the track adjuster cylinder the looser the track the more it pulled to that side maybe you should try to loosen a track opposite the side you are pulling to.
 
Hi Undy, It is a common problem I have experienced with all the mechanical driven snowcats I have owned. At least with the Pisten Bullys there is a fine adjustment steering pot that will help correct tracking.

I would agree with DDS that you can try different tensions on the tracks as this may be the "fix" for other issues causing poor tracking. On the Bombi and I believe also the SkiDozers the angle of the axel flexiator(spelling?) is critical to the drivability of the machine. Worn torsion axels can cause sagging of the arms too. Any axels that are bent or misaligned will be a problem. On my Spryte and Thiokol 3700 they had a solid front axel that moves when tensioning the track. While both tracks may have the same tension it may have required one side of the axel to be pushed farther forward than the other side so if you didn't actually have the tracks on it would look as if the wheels were trying to turn to the left or right.

I would try backing off of the brake tension so there is no doubt the brakes are not dragging and see how it tracks. if it still turns then you have some other misalignment issue.
 
Thanks for the extra input.

The sprockets are in pretty good shape, and even from side to side.

The front flexitors are somewhat toed-in. I'm pretty sure I got them set at the correct angles, but they are definitely worn. With my budget, they'll probably have to suffice for now.
 
Undy,

On our Ski Dozer the flexators are toed out under track tension. Might want to check and see if they are actually toed in.... We welded a steel spacer block on the frame inside the flexator, keeping it alined and the wheel from toing out as it is being pulled by track tension to the rear and back towards the frame. The flexator rides along the block as it swings, keeping it alined. It is a short term fix, but worked well untill we replaced the flexators in the front. They are different and heavier larger units than the others behind those front idlers...

Before this fix, it was indeed pretty easy to run a track off to the outside of the machine if you hit an obstical, even a small one, with the outside edge of the track. Don't ask me how I know this.:glare:

Budget fix for this issue. :whistling: But maybe should be temporary...

Regards, Kirk
 
Hi Kirk,

I guess it's early here still. Yes, you are correct, the front flexitors are toed OUT. Those spacers were already installed when I got the cat.

Looks like I may be needing a new budget, eh?
 
Yea they aren't cheap either.... I am thinking around 1500 for the front pair new. Have to check with boogie on those. The synthetic compound in them that makes them a spring will take a set over the years. Especially if the tracks are tensioned year around. Good idea to loosen them in the off season.

Regards, Kirk
 
Okay, I'm getting somewhere. The cat rolls freely, and relatively straight. But when I run the engine, I'm getting pressure on the left brake. (This cat had both the hydraulic rams plus brake master-cylinder rams for steering. I removed the brake master-cylinder system, so I've got hydraulic brake steer only.)

Both brake slaves push out somewhat, but the left pushes out more. I can compress both by hand, but the left side requires more pressure. So I'm assuming I've got problems in the hydraulic control perhaps? Can anyone confirm this assumption for me? Is there a way of testing the brake circuits to ensure that they are performing as they should?

Looking at the manual, there appear to be two o-rings for each valve. Is this something I should be tearing into and fixing myself? Or is this a job for a hydraulic shop?
 
the hydraulic actuators are simple to pull apart and rebuild as long as you don't have any wear or pitting that will require machining out to get them to seal. my Thiokol actuators are dribbling a little bit. I plan on a rebuild and relocation next summer
 
Thanks Don. I guess I'll tear into them. Do you know, are the O-rings common items to find or are they best sourced from the mfgr.?

I'm all fired up. We rebuilt the carb last summer, but it's been pretty doggey in mid-throttle. I adjusted the linkage to the accelerator pump and it seems very much improved. Hopefully this hydraulic issue gets solved as painlessly.
 
it sounds as if you have something by passing in the spool valve I think you will be able to find everything you need at your local hydraulic shop. But some one like boggie could likely tell us if there is any thing special about them. I think it's a safe bet your bowman o ring kit wont work but a hydraulic specialty shop or a parker shop should have the required cups you need as long as you have good residue to match up you may need a wheel cylinder ball hone to clean and re crosshatch the bores again too.
 
dds said:
it sounds as if you have something by passing in the spool valve I think you will be able to find everything you need at your local hydraulic shop. But some one like boggie could likely tell us if there is any thing special about them. I think it's a safe bet your bowman o ring kit wont work but a hydraulic specialty shop or a parker shop should have the required cups you need as long as you have good residue to match up you may need a wheel cylinder ball hone to clean and re crosshatch the bores again too.
Click to expand...

The double backed slaves used on these have a spring inside of each of them
Unless one is weak or broken when all controls and at rest the cylinders should not be moving

If they are make sure you are not getting any back pressure on the hydraulic portion of the system it should be going straight to tank unless you pull one of the steering handles in the front of the seat ( the hydraulic ones )
 
Hi Brad. Thanks for your input.

I've got a neighbor who's hunting up pressure gauges for me to use. But I'm thinking through the problem, and considering how to diagnose the problem.

If I've got a restriction in the line back to the tank, then both slaves should be seeing higher pressure than normal.

But if I've got some restriction in one steering control or line, preventing normal flow back to the tank and causing pressure in one slave, then I could swap lines (left for right) at the slaves and expect to see the problem occur in the opposite slave?

Similarly, if the problem stays with the same slave, that would point to a problem in the effected slave, such as a weak/broken spring.

Is it also possible that I've got mismatched pressures coming out of the splitter which supplies fluid to the two steering lines? I'm thinking that I could check this by reversing those lines at the splitter.

Am I thinking this through correctly, or am I all wet?
 
Okay, a little more progress(?).

With engine off, the slaves are compressed fully. When I start it up, the left slave extends by about 1/2", the right by about 1/4". Once I operate the levers, the left slave stays extended by about 3/4" and the right stays at 1/4"

I swapped the lines at the slaves, right for left, so the left control operates the right slave and vice versa. The left slave still was extended further than the right. I interpret this result as pointing to the slave as being the problem, since it didn't matter which line I used.

So I removed the slaves and tore them apart. I found some pitting on the right slave, so I'll have to deal with that. I figured Brad's comment about a bad spring might be correct. But I compared the compression strength of the return springs, and if anything, the left cylinder spring was stronger. It also seemed to move freely on it's shaft. Despite this, the left slave is the one that doesn't return fully. ??

So if both lines act the same, and the slave seems to retract okay, then I didn't figure out why the left one extends more than the right one when the engine is running.

But one curious thing happened after I removed the slaves. The right line proceeded to leak fluid, while the left line did not. I plugged them both to keep from losing hydraulic fluid. But I'm wondering whether the left line NOT leaking might point to a restriction somewhere?

I'm still awaiting the hydraulic pressure gauge/s, and intend to check what sort of pressures are occurring.

Any ideas?
 
Old Hydraulic hoses have been know to swell shut reducing flow or even closing it off. Since only 1 hose is leaking fluid I would suspect this. Especially if that the hose is very old, like original. Pressure gauge should tell.
 
A brake wheel cylinder hone may take care of the pitting. On our 252 the clutch slave cylinder was saved with this and a 75 cent piston cup seal...

Regards, Kirk
 
the left cylinder is extending more because of brake band wear. just adjusted mine on the 2100. next question do you have bleeder valves on your slave cylinders, if you do run through your braking than release the brakes, crack the bleeder on the side not retracting see if the cylinder retracts, if it does you have a restriction if it does not or continues to puke fluid even after it has retracted you are leaking pressure through your control valves.
 
Kirk,

I'll probably try to hone the slave. But I tried to hone the manual slaves (this cat had both hydraulic-powered slaves PLUS manual powered slaves) with no luck (and that's why I removed the manual powered slaves and only retained the hydraulic system). The pits just kept growing. Can't hurt to try on this one, and have someone re-sleeve it if necessary.

Don,

I'm not certain that the cause is just brake wear. The extension shafts I made to replace the manual brake slaves are adjustable, and I've adjusted those to compensate for what I assumed was uneven brake band wear.

Curiously, when the engine is on, and the slaves are somewhat extended, it takes more manual effort to collapse the left side than the right. ?? But this is the case, no matter whether that slave is attached to the right or left side hydraulic line.

I do not have bleeders on the slaves. I did burp the lines at the slaves, and I don't think air is the issue. Once the engine is shut off, both slaves fully collapse immediately.

Come on pressure gauges!
 
you could have a return restriction but I would think the problem lies in the control spools as there should be no flow to the rear with the spools released
 
You must log in or register to reply here.
Top