Chassis construction photos from Don and welding on your FT

Topic: Chassis construction photos from Don and welding on your FT (Read 5498 times) previous topic - next topic

Re: Chassis construction photos from Don and welding on your FT

Reply #25 – January 12, 2012, 03:38:42 pm

Maybe a thin coating of the paste used in electrical connection of alum and copper wires would provide protection after all the prep work and painting is done in final installation. I also use pure copper sulphate on many connections on the coach-elec/frame/bolts etc and have found so far this works well. Anyway, very interesting reading and thought process by all, and I am sure FOT are reading and stealing some ideas from you all.I personally think Don is right in that keep any moisture away from joints and you have it beat (as best as humanly possible)
John

Re: Chassis construction photos from Don and welding on your FT

Reply #26 – January 12, 2012, 03:39:33 pm

Quote

Excellent point! I think the corrosion could be mitigated by using some sort of insulation. Fasteners could still be a problem, however. Teflon washers, maybe?

Teflon could mitigate 99% of the potential problem. But that leaves the most critical part vulnerable: the shank of the bolt. Us anal engineers might try some silicon in the donut made because the hole is a bit larger than the diameter of the bolt....

best, paul

Re: Chassis construction photos from Don and welding on your FT

Reply #27 – January 12, 2012, 04:48:54 pm

Quote from: Kent Speers – January 12, 2012, 03:37:53 pm

Don, my only point was that if the area being repaired is an integral part of the monocoque structure, I would check with engineering at Foretravel to see if you need to tie the glass, insulation, metal framing and bay flooring glass together. If you use the POR 15 on the steel structure, you may not be able to get an adequate bond between the metal, the skin, and the foam.

I think that the Roloks were there for the express purpose of tying these parts together; why else use them? If the design engineer didn't envision strain on this joint then they would have simply used screws. So if they worked before then they (or something similar) would still work. I do agree that there does need to be a good mechanical bonding between all those bits but I think that fasteners would do the job. In fact, at least from a corrosion standpoint, the POR 15 will help.

However, as far as Don's theory about keeping moisture out of the area... I don't think it's possible to keep moisture out given the environment (wet roads, salt, humidity, sand and gravel, etc.). I think I'd try to mitigate galvanic corrosion as much as possible by insulating the dissimilar metals from each other. I would make sure that the aluminum bits and the steel bits never touch. Whatever you do, do not "bond" aluminum and steel together!

Teflon washers and silicon would be an easy and cheap solution.

But I also agree that a phone call to FOT or MOT would be a good idea.

Craig

Re: Chassis construction photos from Don and welding on your FT

Reply #28 – January 12, 2012, 05:57:59 pm

Craig,

I really like your popsickle stick and paper model idea. I once did a finite element analysis (FEA) of a space-frame touring bus (Prevost like). It used frame elements with a similar section to what Don has found in his Foretravel. The structure was plenty strong but wasn't very stiff. Then I added the fiberglass outer skin and the stiffness was dramatically improved. As you know, the skin adds stiffness and the fasteners used to adhere it add damping. The net effect was a much higher resonant frequency. What you say about girders versus trusses where the strength can be maintained in the direction needed while greatly lightening the structure also rings (so to speak:)). If it's stiff and light, then it resonates at a higher frequency and will be that much more insulated from road inputs. The net effect is better ride and handling and metal fatigue resistance. An alternative to the fiberglass skin is to add diagonals to adjacent corners; i.e., turn all those rectangles into triangles. I'm with everyone on the dissimilar metals idea too, and on the idea that you can't keep water out. This is why if it were me I'd add some diagonal 1.5" members, or some sheetmetal skin (14 gauge), or some gussetting as in Barry's coach, and I'd leave ample room for water to escape. Don, you're doing excellent work. Looks really good. Please forgive me for my eng'r ways. I simply can't resist commenting on a project of this nature. Excellent work and thanks for the photos!

David Brady
'02 Blue Bird, Wanderlodge LXi
NC

Re: Chassis construction photos from Don and welding on your FT

Reply #29 – January 12, 2012, 06:15:49 pm

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I once did a finite element analysis (FEA) of a space-frame touring bus (Prevost like).

"Finite element analysis" sure brings back memories of my 4 years at UCB. In fact, we just returned from the funeral of Jerry Goudreau who headed a group at LLNL developing FEA code that was used for nonlinear FEA of car crashes - thereby saving auto manufacturers big $$$ (it reduced the number of actual test needed - the code was actually developed for weapons purposes). Professors Bob Taylor and Karl Pister and others were there.

best, paul

Re: Chassis construction photos from Don and welding on your FT

Reply #30 – January 12, 2012, 06:42:20 pm

From all this engineer talk maybe FT needs to let contracts to some Real professionals that have real world experience.

Gary B

Re: Chassis construction photos from Don and welding on your FT

Reply #31 – January 12, 2012, 08:12:53 pm

Don... travelite's suggestion of improving stiffness with corner bracing sounds like it might be a great idea. It would add very little weight and cost almost nothing (probably just use scraps from what you've cut for the frame members). Even if you just installed two in opposite corners of each rectangle.

Craig

Re: Chassis construction photos from Don and welding on your FT

Reply #32 – January 13, 2012, 11:16:01 am

Quote from: wa_desert_rat – January 12, 2012, 08:12:53 pm

Don... travelite's suggestion of improving stiffness with corner bracing sounds like it might be a great idea. It would add very little weight and cost almost nothing (probably just use scraps from what you've cut for the frame members). Even if you just installed two in opposite corners of each rectangle.

Craig

Good point and one that Kenworth failed at. Fishtails are very important in adding strength to to anything your welding on. My old Kenworth had a cracked frame because the Kenworth engineers forgot that stuff. But some good old southern engineering and welding fixed things up.

Re: Chassis construction photos from Don and welding on your FT

Reply #33 – January 13, 2012, 11:43:49 am

Quote

Don... travelite's suggestion of improving stiffness with corner bracing sounds like it might be a great idea. It would add very little weight and cost almost nothing (probably just use scraps from what you've cut for the frame members). Even if you just installed two in opposite corners of each rectangle.

If I understand the proposed construction, the aluminum plates would do a great job of increasing lateral shear stiffness parallel to and below the plane of the FT's frame, if attached with enough bolts - say every 6 inches. This also means the length of the aluminum plates should be a least a long in the direction perpendicular to the length of the FT as their length in the long direction of the FT.

This assumes the lower tubular framing is well-connected to the FTs frame above. Such as vertical steel-framed shear panels up to the frame.

best, paul

Re: Chassis construction photos from Don and welding on your FT

Reply #34 – January 13, 2012, 04:59:47 pm

I think Don is doing the right thing by replacing the rusty metal and doing it properly. I think the fiberglass skins no matter how thin add strength to the structure if properly bonded. If one steps back from the coach and looks at the cargo compartments with the doors open, they are a lot like a cardboard box without any ends, and a box like that folds up flat very easily. The coach does have a rigid metal structure at the ends near the wheels that prevents that from happening. The basement floor is fastened in place at the front and rear with horizontal bolts, and it is held up in the middle with vertical bolts into the bulkheads. I have never checked, but the top of the middle bulkheads are probably bolted to the main cabin floor from above. All the rectangular tanks once in place will add some resistance to the cargo floor moving fore and aft. There is also one fore and aft vertical bulkhead in my coach that forms the back of the battery compartment that should add rigidity to these compartments. One should be able to bond the skins to the metal frame by using epoxy. Epoxy bonds to metal much better than polyester resin will and also will bond to the polyester resin skin. On the top skin one could just place bags of sand to apply pressure until it cures. The bottom skin presents more of a problem and should be done first, but an old or cheap air mattress or two should be able to lift the skin into place and apply enough pressure until it cures. One could paint the tubing and sand to bare metal for the epoxy, or sand blast and coat all the metal with epoxy, maybe a bit of overkill though. Definitely put the foam back in place as it insulates the tanks.

Re: Chassis construction photos from Don and welding on your FT

Reply #35 – January 13, 2012, 05:11:48 pm

I should add something. The foam should also be bonded to the skins. Do a test on a scrap piece to make sure the foam is not dissolved by the uncured epoxy. I don't think epoxy will do that, but uncured polyester resin will dissolve some foams.

Re: Chassis construction photos from Don and welding on your FT

Reply #36 – January 13, 2012, 07:10:23 pm

Quote from: Jerry Whiteaker – January 13, 2012, 05:11:48 pm

I should add something. The foam should also be bonded to the skins. Do a test on a scrap piece to make sure the foam is not dissolved by the uncured epoxy. I don't think epoxy will do that, but uncured polyester resin will dissolve some foams.

Jerry, you are correct, epoxy should be used and any 100% solids (no solvent) epoxy should not melt the urethane foam. If the skin is polyester, then go ahead and glass with polyester resin but try to use one with similar physical properties. I hope that Foretravel used epoxy resin but maybe not.

Rather than using the POR 15 for rust proofing, a good application of epoxy resin will be more effective and allow for a better bond to the skin and the foam. Remember, epoxy is the coating of choice for coated rebar in bridge construction.

Re: Chassis construction photos from Don and welding on your FT

Reply #37 – January 14, 2012, 04:28:05 pm

Craig et al.,
Regarding the question of galvanic corrision: I do think I will be able to keep moisture out of this area, but the talk of galvanic corrosion got me thinking about some things, so I did some research... just in case. It appears that the chances for corrosive damage to the steel is almost nil in this configuration. First of all, it is the aluminum that would be the annode in this scenario and the corrosion would be mostly limited to the point of contact. Secondly, since the Aluminum is right next to mild steel in the Galvanic series, there isn't much difference in voltage potential, meaning the galvanic action would be very slow, but in any case would be protective of the steel. Also, the aluminum plate which I plan to use is 3/16" thick and any corrosion will be a long way down the road, even if moisture was persistently present (but I am determined to mkae sure that doesn't happen!).

Finally, if it is likely to be a problem, why would Foretravel use a piece of aluminum trim "inside" the bulkhead joint? You might say so that it would be the sacrificial anode and protect the steel exposed to road salts and the like, and that does make sense to me... but that doesn't explain the substantial 1/8" thick extruded anodized aluminum bottom sill trim which runs in direct contact with the steel frame along both bottom edges of the coach, electrically connected by many screws, as well as all of the bay door trim that holds the struts and weatherstriping, all screwed into the steel framework. Could be that Foretravel missed that one, but I don't think so. I have been too busy working the project to post more, but I will in the near future. In the mean time, I appreciate all the comments- which I take in the spirit in which they have been given. That is to say, out of concern for the wellbeing of one of our beloved Foretravel coaches

Don

Quote from: wa_desert_rat – January 12, 2012, 04:48:54 pm

I think that the Roloks were there for the express purpose of tying these parts together; why else use them? If the design engineer didn't envision strain on this joint then they would have simply used screws. So if they worked before then they (or something similar) would still work. I do agree that there does need to be a good mechanical bonding between all those bits but I think that fasteners would do the job. In fact, at least from a corrosion standpoint, the POR 15 will help.

However, as far as Don's theory about keeping moisture out of the area... I don't think it's possible to keep moisture out given the environment (wet roads, salt, humidity, sand and gravel, etc.). I think I'd try to mitigate galvanic corrosion as much as possible by insulating the dissimilar metals from each other. I would make sure that the aluminum bits and the steel bits never touch. Whatever you do, do not "bond" aluminum and steel together!

Teflon washers and silicon would be an easy and cheap solution.

But I also agree that a phone call to FOT or MOT would be a good idea.

Craig

Re: Chassis construction photos from Don and welding on your FT

Reply #38 – January 14, 2012, 04:48:25 pm

Don, good job and interesting topic. Hope you are taking lots of pics for a later-show and tell!!
Have you got any of the bulkhead area you had to fix that we can see now?
Glad I do not have any of these issues as mine is tight and dry.
John H

Re: Chassis construction photos from Don and welding on your FT

Reply #39 – January 14, 2012, 05:50:45 pm

Quote from: acousticart – January 14, 2012, 04:28:05 pm

Craig et al.,
Regarding the question of galvanic corrision: I do think I will be able to keep moisture out of this area, but the talk of galvanic corrosion got me thinking about some things, so I did some research... just in case. It appears that the chances for corrosive damage to the steel is almost nil in this configuration.

I thought aluminum and steel were farther apart but hadn't look at the chart in years. At any rate, the aluminum plate is a much better idea than wood.

Mostly we were all just talking through potential problems and, like engineers everywhere, thinking about the worst case scenario and how to avoid it. You have a good handle on what you're doing so don't mind us.

Craig

Re: Chassis construction photos from Don and welding on your FT

Reply #40 – January 14, 2012, 08:41:12 pm

Don, there's another material you might consider instead of 3/16" aluminum panels. Blue Bird (BB) Wanderlodge uses this material on the inside of walls to add structural stiffness. It's a urethane fiberglass composite panel: Coosa Composites, LLC - Manufacture of high-density, fiberglass-reinforced I'm sure other manufacturers make similar products. You won't have the galvanic issues, it doesn't rot, it's light, and it provides structural stiffness. BB bonds it with structural adhesive (Sikaflex 221) and Tek screws.

Craig's right as usual, us engineer types are looking for Penn State Altoona, STURAA, (Surface Transportation and Uniform Relocation Assistance Act), 12 year/500,000 mile toughness.

The kind of service most motorhomes will never see!

David Brady
'02 Blue Bird Wanderlodge LXi
NC

Re: Chassis construction photos from Don and welding on your FT

Reply #41 – January 15, 2012, 01:46:09 am

What's the deal with STURAA? Just curious...I'm from Altoona. As a boy I used to ice skate on the campus pond. I'm sure they don't allow that these days.

Re: Chassis construction photos from Don and welding on your FT

Reply #42 – January 16, 2012, 10:59:56 am

Quote from: Dwayne – January 15, 2012, 01:46:09 am

What's the deal with STURAA? Just curious...I'm from Altoona. As a boy I used to ice skate on the campus pond. I'm sure they don't allow that these days.

Not sure Dwayne, I don't have any involvement. I think Altoona Sturaa testing is going strong, testing buses for anyone who wants to listen, and for municipalities and government agencies that are required to buy buses that pass the testing. There's a lot of info on their website. They do a good job, nothing emerges unscathed, a lot of failures of the suspension control arm pick up joints, as we're describing in this thread.

David Brady
'02 Blue Bird, Wanderlodge LXi
NC

Re: Chassis construction photos from Don and welding on your FT

Reply #43 – January 29, 2012, 05:44:28 pm

Hi all,
I have been busy grinding rust and prepping for the replacement of some of the metal subframe parts and am close to being ready to tack weld some new pieces in prior to finalizing the welds when my son has the time. Today I have a few questions regarding the welding disconnect list and the location of some of the components... to start with, here is the list that pertains to our coach;

Disconnect the following before welding on completed coaches:

U270/U280/U295 - B-21 - Alternator ground at alternator
C-2 - Transmission ground at breakerboard
Allison ECU - Under dash / driver's side / both plugs
ABS - 3 plugs in brake ECU - Power in / Front axle / Rear axle
HWH -All grounds on coach and engine batteries

Here is the list with followed my comments/questions in parenthesis;
U270/U280/U295 - B-21 - Alternator ground at alternator (self explanatory)
C-2 - Transmission ground at breaker board (Does this refer to the electrical panel just inside the entry door next to the steps? It is difficult to see all of the connector labels because many are obscured by wires, but I don't find a "C-2" upon my initial examination.)
Allison ECU - Under dash / driver's side / both plugs (See picture, but my ECU seems to be mounted street side on the rear wall of the cargo compartment, not under the dash; and it has three large plugs- a grey, a black, and a blue. I am wondering if earlier coaches had just two plugs and the under dash location....)
ABS - 3 plugs in brake ECU - Power in / Front axle / Rear axle (I believe this refers to the black box mounted to the ceiling of the cargo compartment curb side near the center that says Midland-Grau ABS on it)
HWH -All grounds on coach and engine batteries (not sure what this refers to... the ground wires on the outside of the silver HWH Aluminum box just forward of the ABS ECU? As well as the starting battery grounds?

Any insight to the location of these components will be appreciated!
Don

Re: Chassis construction photos from Don and welding on your FT

Reply #44 – January 29, 2012, 10:52:14 pm

Quote from: acousticart – January 29, 2012, 05:44:28 pm

U270/U280/U295 - B-21 - Alternator ground at alternator (self explanatory)
C-2 - Transmission ground at breaker board (Does this refer to the electrical panel just inside the entry door next to the steps? It is difficult to see all of the connector labels because many are obscured by wires, but I don't find a "C-2" upon my initial examination.)
Allison ECU - Under dash / driver's side / both plugs (See picture, but my ECU seems to be mounted street side on the rear wall of the cargo compartment, not under the dash; and it has three large plugs- a grey, a black, and a blue. I am wondering if earlier coaches had just two plugs and the under dash location....)
ABS - 3 plugs in brake ECU - Power in / Front axle / Rear axle (I believe this refers to the black box mounted to the ceiling of the cargo compartment curb side near the center that says Midland-Grau ABS on it)
HWH -All grounds on coach and engine batteries (not sure what this refers to... the ground wires on the outside of the silver HWH Aluminum box just forward of the ABS ECU? As well as the starting battery grounds?

Any insight to the location of these components will be appreciated!
Don

Don,

Not sure what C-2 is, but also check the main DC distribution board at the front of the street side center compartment (behind the white fiberglass cover).

Our Allison TCU is where yours is, as is the ABS controller. I would just disconnect all cables from all controllers you can reach, and then pull the grounds from the coach and engine batteries. I think you can pull the cables from the HWH controller (silver box on the ceiling of the bay) if you unscrew the cover. I would also disconnect the cable from the HWH control panel in the dash, and if you really want to play it safe, maybe lift the Allison control panel (one with the joystick) and disconnect the cables from it.

I think if your welding ground clip is very close to the work area there shouldn't be much problem with induced current in the wiring. Where you could get into trouble would be if you clipped the welding ground to the frame at the engine and then welded far away.

Re: Chassis construction photos from Don and welding on your FT

Reply #45 – January 30, 2012, 01:51:11 pm

Thanks Dave,
That is helpful info... I was puzzled by the instructions to disconnect both plugs under the dash when the Allison ECU has three, but perhaps earlier years had just two and were located under the dash. Your thinking about the ground clamp location and disconnecting the various "brains" and battery grounds makes sense to me, so that is how I will proceed.
Don

Quote from: Dave Katsuki – January 29, 2012, 10:52:14 pm

Don,

Not sure what C-2 is, but also check the main DC distribution board at the front of the street side center compartment (behind the white fiberglass cover).

Our Allison TCU is where yours is, as is the ABS controller. I would just disconnect all cables from all controllers you can reach, and then pull the grounds from the coach and engine batteries. I think you can pull the cables from the HWH controller (silver box on the ceiling of the bay) if you unscrew the cover. I would also disconnect the cable from the HWH control panel in the dash, and if you really want to play it safe, maybe lift the Allison control panel (one with the joystick) and disconnect the cables from it.

I think if your welding ground clip is very close to the work area there shouldn't be much problem with induced current in the wiring. Where you could get into trouble would be if you clipped the welding ground to the frame at the engine and then welded far away.

Re: Chassis construction photos from Don and welding on your FT

Reply #46 – February 09, 2012, 10:56:11 am

Don,

I was thinking about your project, and installing the aluminum panels. I'd recommend the use of 3M VHB tape. There are many varieties of it, some costing several hundred dollars a roll, but the stuff you can buy at any auto paint place is incredibly strong. The 1/2" X 20' long drive rack on my cnc router is attached with this stuff, no bolts. I had to remove a section of it and it took a 3' crowbar and some bent metal to do it. This drive rack engages pinion gears that hurtle the gantry and spindle, some 300 lbs of it, back and forth at high speeds, sometimes changing direction several times a second. VHB tape is what semi trailers are put together with, the skins and framing, skyscraper facades, aircraft. No muss, no fuss, no screws, permanent and it insulates the alum from steel.

http://solutions.3m.com/wps/portal/3M/en_US/3M-Industrial/Adhesives/Product/Bonding-Tapes/VHB-Tape/

Lots of this stuff available on ebay.

Chuck

Re: Chassis construction photos from Don and welding on your FT

Reply #47 – February 09, 2012, 12:38:15 pm

Chuck, that is some impressive tape! Checked out some YouTube videos and was pretty blown away by the demos...
Don

Quote from: Chuck Pearson – February 09, 2012, 10:56:11 am

Don,

I was thinking about your project, and installing the aluminum panels. I'd recommend the use of 3M VHB tape. There are many varieties of it, some costing several hundred dollars a roll, but the stuff you can buy at any auto paint place is incredibly strong. The 1/2" X 20' long drive rack on my cnc router is attached with this stuff, no bolts. I had to remove a section of it and it took a 3' crowbar and some bent metal to do it. This drive rack engages pinion gears that hurtle the gantry and spindle, some 300 lbs of it, back and forth at high speeds, sometimes changing direction several times a second. VHB tape is what semi trailers are put together with, the skins and framing, skyscraper facades, aircraft. No muss, no fuss, no screws, permanent and it insulates the alum from steel.

solutions.3m.com/wps/portal/3M/en_US/3M-Industrial/Adhesives/Product/Bonding-Tapes/VHB-Tape/

Lots of this stuff available on ebay.

Chuck

Re: Chassis construction photos from Don and welding on your FT

Reply #48 – February 24, 2012, 05:32:28 pm

I have been making some progress- slow progress, but progress nonetheless! I thought I would post a few some pictures for your entertainment... some are from earlier in the process, the latest from today. Light at the end of the tunnel? You decide. For me, I am seeing it!
Don

Re: Chassis construction photos from Don and welding on your FT

Reply #49 – February 24, 2012, 09:56:55 pm

Looks like you are just about at the end of the tunnel. Nice work and clear photos! I close my eyes when I look at my compartments and bulkheads now.

Hip, Hip

Pierce

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