frustrated new scrambler owner

[airstreamer74]

Frustrated with my Scrambler

OK, I bought a used scrambler; vanguard 16 started and ran good, but no drive belt. Prior owner was not honest with me, but I won’t rehash that. I put a belt on it, ran good in a straight line, but wouldn’t turn. I tightened compression spring nuts to add pressure to the clutch plates but still not enough. The “engaged” clutch plate just sits there and spins till it smokes. OK, after reading all-things-scrambler on this site and anywhere else, I gave in and tore it apart, ground off all the old (very little) clutch material, bought a sheet of high-friction material from McMaster-Carr:

Stock # 60895K21 HI Friction Molded Brk & Clutch Lining Sheet .55 Coefficient of Friction, 1/8" Thick, 15" X 15" In stock at $55.00 Each

and used Industrial JB WELD to apply about ten times the amount of material that was there before. Finished putting the driveline back together last night, started it up and….. it’s like I didn’t do a thing. It will go in a straight line, but as soon as you turn the wheel and all the power goes to one side, the vehicle slows and the power side starts spinning. It was dark and I didn’t have the lights hooked up yet so I didn’t take it fast yet, but if it’s like before, when your going fast, it just goes in a straight line no matter which way you steer it. I even have the compression springs tightened to the point where it’s hard to turn the steering wheel.

HELP!!! Anyone????

Airstreamer 74

[jpswift1]

Larry W. knows Scramblers very well......he'll probably chime in and help you out.

[thebuggyman1]

The clutch material you replaced was for driving each set of wheels, there should be another for stopping each side. Scramblers have issues with the hydaulics. You do not need to have the engine running to check how the steering works, watch it and learn. I'll bet you don't see anything happen when you operate the steering. Good luck

[airstreamer74]

I understand the mechanics of the driveline very well; the brakes, clutches, etc. I have studied the exploded schematics, torn it apart and put it back together again, watched it operate perfectly while up on jacks; with no resistance, everything worked as it should. This is why I finally resorted to tearing it down and replacing the clutch material (brake pads were still good) cause I figured there just wasn’t enough friction there to overcome the torque when turning; the tire grip and all that.

But I think it may have something to do with what LarryW mentioned back when I first had the problem. I think the entire driveline frame may be flexing when a turning slave is activated. I’ve concentrated on watching the side which is activated (which it is) and then watching the other side as it slips (which it shouldn’t). Instead, I need to watch the right side as I turn left and vice versa to see if the side which shouldn’t move, does in fact move or flex. It makes sense. It goes in a straight line fine, as long as there is pressure on both clutch sets coming from both ends. But release the pressure from one end and you loose it at the other if the frame is allowed to flex.

Alright, I’ve got something to try at least.

[LarryW]

It looks like maybe the brake part of the system is not working. Do you have it shimmed properly with the little c clips? If not the outer plate will be loose and not hit the brake part of the system very hard. The frame part does flex if you have the springs inside the tubes real tight as it sounds like you did. I did the same thing there and then I eventually loosen them up with no bad side affects. The clutch plates still gripped good and the steering was a lot easier. I would check out the slope in the outer brake diamond looking things. If they are loose slip some c clips in there and I bet it will work. Let me know. I will keep and eye on the thread and try to help you best I can.

[LarryW]

After thinking more on it. I know you said you understand it but thought I should mention the tigher the springs are the less it will brake and more it will engage the clutch. Sounds like it is disengaging but not braking. If you loosen the springs and make sure the c clip shims are shimmed correctly then I am pretty sure it should turn. When working right it should turn on pavement even. I dont recommend it if you can avoid it but it will.

[airstreamer74]

I haven't got to the "brake" part of the steering yet. If I understand the scrambler steering mechanics correctly, it's a 2-stage operation; first turn the steering wheel a little and the driven plate is pulled away from the drive clutch plate, removing the drive power so it's "freewheeling" on that side, and then if you turn the wheel more the driven plate on the freewheel side is pulled against one of the brake pads to lock up that side. I haven't got to test that yet because even though the fist stage seems to work on the freewheel side, the power side then slips so I go nowhere.

I had a chance this evening to turn the steering wheel and watch for any flexing. I can't see any. That's not to say that it isn't happening, I just can't detect any with my 45 year old eyes.

I'll try loosing up the tension on the springs and see what happens. If that doesn't work maybe think about a cross member.

[thebuggyman1]

You have the theory correct. First stage disconnects the drive clutch and will give minimal steering. Second stage applies the brake to that side, this is where all the turning happens.

[LarryW]

So the brakes dont work yet. But when you try to turn it just stops? Same both ways you turn? I missed that part I guess. You are right with the springs needing to be tighter. I wonder if the friction material is correct friction?

[airstreamer74]

If I start from a stop, turn the wheel (lets say left but it doesn't matter), hit the gas, left side is disengaged, right side is engaged, but clutch spins just like the left. If I'm going slow, and I turn, same things but slows to a stop. Not a sudden stop like hitting the brakes.

[airstreamer74]

Regarding the friction material, it's good stuff. $55 for a 15x15x1/8 sheet from McMaster Carr. Read about old tractor buffs using it to rebuild clutches and brakes as well as motorcycle buffs ising it to rebuild their own brakes.

[jerseybigfoot]

1.The clutch plate with the sprocket (movable side) has to be be in good condition with a non pitted surface.
2.The 2 bolt bearing retainer and bearing on the end of the movable side has to be in good conditions well as the small pilot bearing. very often the bearing is loose in the bearing retainer and the spring force is lost due to the slop.
3. The friction ring created by the friction material can also be too large and will loose the force per square inch. the surface should be only about 1" from outside diameter to inside diameter.
4. too much force will warp the clutch plates and make them into dishes and you will loose surface area. The plates should be flat.

[airstreamer74]

1.The clutch plate with the sprocket (movable side) has to be be in good condition with a non pitted surface.
2.The 2 bolt bearing retainer and bearing on the end of the movable side has to be in good conditions well as the small pilot bearing. very often the bearing is loose in the bearing retainer and the spring force is lost due to the slop.
3. The friction ring created by the friction material can also be too large and will loose the force per square inch. the surface should be only about 1" from outside diameter to inside diameter.
4. too much force will warp the clutch plates and make them into dishes and you will loose surface area. The plates should be flat.

1. It was in good condition.
2. All good, no slop
3. I hate to disagree with someone who knows far more about 6x6s than I do, but:
The basic equation for clamp load on an axial type clutch is:

T = (F) x (mu) x (D+d)/2

where: T = torque
F = clamp load
mu = coeff. of static friction
D = OD of friction surface (clutch disc OD)
d = ID of friction surface

In other words, increase the clutch material surface area to decrease the required clamping force.

And from a Drag racing web site: “The torque capacity of any clutch is based on three basic parameters: clamp load, surface area, and coefficient of friction. Increasing any of these factors (like surface area) allows the designer to change the other two variables. As an example, by doubling the clutch surface area with the same coefficient of friction, a single-disc clutch that can hold 500 lb-ft can now reliably hold 1,000 lb-ft.”

4. This is definitely a valid concern, thanks.

[airstreamer74]

My mistake, I said:

The basic equation for clamp load on an axial type clutch is:

T = (F) x (mu) x (D+d)/2

where: T = torque
F = clamp load
mu = coeff. of static friction
D = OD of friction surface (clutch disc OD)
d = ID of friction surface

I said: In other words, increase the clutch material surface area to decrease the required clamping force.

That was wrong: (D+d)/2 is not clutch material surface area; it is average diameter of the clutch material. So increasing the clutch diameter would help, but it has nothing to do with total surface area. So I think the statement from the drag racing website were just plain wrong. Hummmm.

That will teach me to spout off.

OK, I'm stumped again

[thebuggyman1]

Where are you located? Maybe someone close by has some scrambler experience and could help.