| Author | Message | ||
| Darrell Black, DVM (Darrelldvm)
Rating: N/A |
Just where is the ground on the rear bulkhead? Are we talking about the ground in the battery compartment? | ||
| FAST FRED Rating: N/A |
On an 06 thats it. I replaced the usual iron bolts with 7/16 copper bolts and flat & lock washers. This has increased the crank rpm in really cold weather , and stabelized the charging from the imbecile coach V reg. No corrosion noticed , so far. FAST FRED | ||
| Joe Bigwind Rating: N/A |
If you look at your starter you'll see one of the big cables is connected to the starter and the rear bulkhead. Or it is on my 4106 and that is where one of my big starter problems was. FF's suggestion sounds good too and think I'll change out my grounding H/W. Joe Shelton | ||
| B. Wayne Rating: N/A |
Look about 12 inches below the bottom rail of the bulkhead. I have found that's where ground is!! HARRR HARRR!!!!  | ||
| mel 4104 Rating: N/A |
as Fstated change out the steel bolt that connects the ground to the rear bulk head and replace it with a copper one of the same size, in fact when you go to buy one get @ and put an extra one from the engine block to another spot one the bulk head. when you replace the bolt be sure toclean up the bulk head real good with an angle grinder to get rid of all the corrosion and dirt and grease, then coat with dialectic battery grease on the bulkhead on both sidesthen coat he washers and the boaltand use never sieze on the nut and bolt,be sure ot use a s big a washer that you can get for both sides of the bulkhead. when you have the cables bolted down tight the coat them good with battery terminal sprayto seal out the moisture and air as this is what will cause the corrosion to return. be sure to clean the connection to the block and starter at the same time. it might be a good time to clean the ground connection in the battery compartnent at this time too.DA book says do it every year but do a good job the first time and not for the next 5-8 years just watch that the corrosion does not start to build up again. the old bus mech. will tell you that this is the main reason for starter and battery trouble a lot of them have been replaced that did not have to be due to the poor ground. | ||
| Stephen Fessenden (Sffess)
Rating: N/A |
Are you all putting that copper bolt through aluminum? Prevost uses a ground bolt welded to the steel frame. Too bad you cannot weld a bolt to the bulkhead or frame around it. | ||
| Richard Bowyer (Drivingmisslazy)
Rating: N/A |
I thought a bronze bolt was to be used instead of copper? They could be brazed if desired and are also non corrosive. Copper is too soft I thought. Richard | ||
| FAST FRED Rating: N/A |
Bronze has much poorer conductivity than pure copper, tho not as bad as SS or iron. It's in Da "Lectric Book. Copper IS quite soft , but merly holding a contact to a bulkhead doesn't require 400lbs of torque , just a snug pressure. I get my pure copper nuts, bolts and washers from the local power company repair guys , works for them too. FAST FRED | ||
| Stan Rating: N/A |
Does anyone know how much voltage drop would occur if your ground conection is a stainless steel bolt welded to the frame? My guess is close to zero. Although the resistance varies with the alloy, when the length of the conductor (the thickness of the bolt head) is less than 1/2" I think the voltage drop on the battery cable will be much greater than the the drop on the bolt. Maybe someone with the inclination to do all the math will work it out. Don't forget that the final return point is the lead battery post. | ||
| Brian (Bigbusguy)
Rating: N/A |
On mine I replaced all the bolts are what ever come with the bus when new. The cable has a flat strap part that is also next to the bulkhead I would think 99% of the amps would go that way and the bolt is only holding it to the bulkhead. I did clean all of the bulkhead connections and used dielectric grease to stop any corrosive action. And my factory cables look like they are tinned in lead so I dont see and copper to bulk head any way. I would just clean it and put it back to factory . It worked for 30 years that way I dont see if cleaned it should not go for 30 more. Brian 4905 Oregon? | ||
| mel 4104 Rating: N/A |
the best way is FF way use the copper bolts and huts and washers instead of stainless or reg. steel bolts. but never weld on the bulk head as the weld will cause you probles, that is why GM rivited every thing. by the way Stan what type of rod do you yse to get a good weld when joining Al to SS? | ||
| Stan Rating: N/A |
Mel: I am sorry that I didn't know the engine cradle and rear suspension on a 4905 were made out of aluminum but that is imaterial. When you bolt a ground cable to a another piece of metal you are not carrying any current on the bolt. The current is carried on the interface between the cable lugs and the metal it is attached to. As Brian pointed out. cable lugs are usually lead plated to resist oxidation. Copper oxide is not a good conductor. No high current loads should be dependent on multiple connections to the framework. Run both positive and negative battery cables to their respective posts on the starter. From that point use a smaller cable to ground and to the electric panel for the small loads. Oxidation in a connection that has little effect on a 10 amp load is critical at 500 amps. | ||
| FAST FRED Rating: N/A |
When the current carring surface on the ground gets a bit corroded , the current will travel thru the bolt to the washer surface on the other side of the bulkhead. Thats why copper works best. Still the simplest test is to hold the shutoff manyally and crank for 15 seconds. Then VERY GINGERLY touch the batt ground terminals and anyplace you can. Anything HOT! is dirty and needs attention. FAST FRED | ||
| Stan Rating: N/A |
Putting on a Band-aid (different kind of bolt) to compensate for bad connections is not the answer. Usually there is a variety of different metals involved (copper bolt, aluminum bulkhead, flat washers of some other material, lock washers of a fourth material) which produces all kinds of electrolysis in the presence of air and water. There will probably be just as much oxidation on the back side of the bulkhead as the front side under the washers. Various sealants to keep the connection dry is the best protection. Common Vaseline will last several years if everything is generously coated before assembly. Commercial products for this are available at all auto parts stores. If you have worked on a recent model car you may have noticed that even the base of the light bulbs is coated with a protective grease. Probably the most important part of this discussion is that many bus owners are not aware that a DD starter does not have an internal ground . It is a two wire device that has to have a cable conection from its negative terminal to ground (battery negative), and does not ground through the engine block. | ||
| Doug Dickinson (Dougd470)
Rating: N/A |
Re ground connections - when using a sealant on a connection, using vasiline can cause you more problems that you will want. You should use a compound like No-Ox or other conductive grease. Some of the battery terminal compounds are conductive. Read the labels to find out. Each is used differently (conductive vs non-conductive). Copper hardware for connecting to a frame or other high current connection works in (more or less) temperature stable environments. The latest thinking on grounding uses stainless bolts with a double hole lug, which gives more surface contact room. THere are several reasons, but I think either will work, IF maintained properly (and grounds, by nature, require a check every so often for tightness and contact). Doug St Louis MC9 | ||
| Stan Rating: N/A |
Doug: The theory of coating the surfaces before clamping them together is to fill in all the irreularities in the suface. The rest of the material is squeezed out and forms a seal around the edge. The material remaing in the joint keeps air and moisture out of the low spots. The high spots (no metal surface is completely smooth or flat) make metal to metal contact and carry the current. Obviously you want to make both surfaces as smooth and flat as is practical but you are looking at sealing the very small sized holes where corrosion begins. The same theory holds true for battery posts. For fifty years I have been coating the posts and all surfaces of the connectors with vaseline and or chassis grease, Put on the connector, tighten snugly and you have a minimum resistance connection that stays corrosion free. Using a conductive coating between dissimilar metals creates a litle battery and that is not good for long life of the connection. | ||
| niles steckbauer (Niles500)
Rating: N/A |
MY WAY - ream smooth the post and cable lug for closest to 100% contact - connect both and apply anti-oxidant on TOP of the connection - coating the post/lug can trap moisture - leaving the bottom open allows for weepage - over time heat will cause the anti-oxidant to seep down from the top and into the voids while not trapping moisture between the lug and connectors - liberal amounts of anti-oxidant on top provides a reservoir to replenish over time - YMMV - Niles | ||
| Tom Caffrey (Pvcces)
Rating: N/A |
About the soft copper bolts: depending on how the bolt is formed, work hardening may make it surprisingly hard. Overdone, it can become brittle enough to break rather easily. The bolts that I have handled have always surpised me a little because of the loads that they could handle; the threads don't strip easily, at all. Solenoid studs are a good example. I like coating the parts with non-conducting lube first, then assembling them. I think that it's more reliable. Our boat has 1/2" copper tubing for it's hydraulic steering and I was all set to take it all out and install hoses until I checked on the burst pressure ratings of the tubing. It seemed that the hose would have been no improvement and the copper went twice the system pressure, so I got over that idea real quickly. More fuel for this fire. Tom Caffrey PD4106-2576 Suncatcher | ||
| Brian (Bigbusguy)
Rating: N/A |
I saw this that is wrong: "I am sorry that I didn't know the engine cradle and rear suspension on a 4905 were made out of aluminum but that is imaterial." On a 4905 The engine cradle and rear suspension is made of a very strong grade of steel and it is bolted and in some spots riveted to the bulkheads that are made of aluminum . All is tied togther with grounding straps. Just wanted to let any one that wanted to know how its realy is put toghter. Brian 4905 Vancouver WA (amtrack depo) | ||
| Stan Rating: N/A |
Brian: I should have put a smiley face after that statement. Obviously you don't need any special kind of welding rod to weld a bolt to the cradle. The whole post was about using a welded bolt as opposed to using a bolt in a through hole. My next post went into a lot more detail. It is much easier to control corrosion using SS bolts, nuts and washers than mixing up various metals and bolting the whole mixture to another unknown alloy, whether ferreous or non-ferreous. If I had to make a high current connection to aluminum, I would weld on an aluminum bolt and then use aluminum washers and nut. If you used a sealed crimp on aluminum lug you would have the best possible. |