If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
Plywood chassis bonded to 'glass body (think "Marcos GT1800") project
I'm working on a project that should make LBC purists and hot-rodders
alike gape, gasp, and guffaw: I have one of Bill Bonadio's "Dio" splashes of the 1959-60 Bill AMes/Dewey BROhaugh AMBRO fiberglass bodies, originally intended for a Triumph TR-2/3 chassis or whatever it would fit on (the body will accomodate wheelbases from 88" to 101", thanks to the trim-able center body pieces), to race in SCCA "Modified" classes. (If you've never seen one, it is dimensionally and sculpturally about as close as a couple midwestern racers could get to a '57 "Knobbly" Lister without generating lawsuits from Brian Lister. I'm sending this message to three different user groups: rec.autos.antique (because of the expertise here on the '64 MGB running gear I'll be using, and because of the obvious connection to the wonderful plywood-chassied Marcos cars), rec.aviation.homebuilt, because I can't think of another group that is likely to have as much knowledge of stressed-plywood and fiberglass construction, and to rec.boats.building, because of the wealth of experience there with plywood and fiberglass craft that don't leak or fall apart in the middle of the pond. I've been trying to get started on this project since I got my "Dio" (AmBro splash) fiberglass body in 1997 (aahhh, why hurry?), but miserable interruptions and daunting pre-tasks like actual money- generating work and my Wreck of the Hesperus garage have kept me in the "design phase" for 14 years -- during which time some of you may have even seen a post or two of mine. Well, I'm 63, retired, have my garage half-cleaned (my wife's half, unfortunately...), I've discarded entirely the idea of building up a steel-tube chassis to drop a small-block into it, and after much research, doodling, modeling sections, I have come to the conclusion that the plywood semi-monocoque and 1800cc MGB engine and drive train are the way to go -- the Marcos GT1800 used (mirabile dictu!) an 1800cc Volvo engine, the same one as in the late, lamented Volvo P1800 (aside from the PV544, the best-looking car they ever made. But I digress...) I have long had an abiding admiration for Jem Marsh and Frank Costin's Marcos semi-monocoque plywood-chassis/bodies, especially the GT-1800, and I found, in Herb Adams' excellent book on chassis design, a stressed skin "2 box plus integrated monocoque side sills and bulkheads" design very much like that of the Marcos GT1800. Adams' design is in steel, and was used for a high-end Cobra replica that wasn't any more exciting than any other Cobra replica: except that its stressed-skin-and-bulkhead chassis had HUGE torsional rigidity (as did the original Marcos and Marcos GT) My running gear donor is a '64 MGB-GT that was rotted to within an inch of its life (so don't fret, "rebuild it from Heritage panels even if all you have is part of the floor" enthusiasts -- it didn't have ANY part of the floor (did have some nice sellables, like the aluminum bonnet, working Smiths heater, several extra 60-spoke wire wheels, etc.), but for MY purposes, and at $250 for the whole MGB-GT w/ complete drive train, INCLUDING the 50-mile tow to my garage, it seemed like the perfect basis, especially as the entire front suspension and steering rack are mounted to a bolt-on crossmember (which itself is mounted to the MG's unit body). By using the front crossmember as a whole unit, all that's necessary is to make sure the crossmember is mounted to maintain the correct kingpin inclination, as is perfectly illustrated in the Bentley manual. Anyway, that's my double-*******ized sweaty-fingered project of the decade. If anyone happens to know of a good website that might be able to help me with the dreary details of this project, please let me know (I'm thinking plywood boat and experimental aircraft builder's forums), I'd be most grateful for any links. BTW, the origination of the Marcos plywood monocoque had a LOT to do with Frank Costin's previous engineering work at DeHavilland, makers of the plywood monocoque DH.98 Mosquito "Wooden Wonder" -- the near-"stealth" invisibility of the plywood Mosquito to "Freya" and various FuG German radars made it an excellent Pathfinder and Night Fighter. Wonder if it works against police radar? I'm not building this to fool anyone, or to represent it as an actual original AMBRO (which has been tried, by the most unlikely person one could think of), it's just going to be a driver. My plan to get it street licensed by the anal-retentively-regulatory CT DMV is to use the matching chassis and engine S/N plates, and call it an "MG Special," like the Lester-MG. Will it work? At 63, will I live long enough to complete it? Who knows, but as my distant -- VERY distant -- relative Robert Browning said: "Ah, but a man's reach should exceed his grasp, or what's a heaven for?” Sorry for the long post. If anyone's interested, I'll be putting up pix of the project elements, design, and build on Photobucket or FlickR. Any suggestions -- other than "get thee to a loony bin" or "go soak your head" gratefully accepted. Peace Bart Brown |
Ads |
#2
|
|||
|
|||
Plywood chassis bonded to 'glass body (think "Marcos GT1800") project
There shouldn't be anything too difficult or dangerous about what
you're describing. Pick your plywood carefully oak might be one choice, unless you run across something else, and select the fasteners/fastening system carefully. You'll want some "give" to the system, so it doesn't self-destruct over a few potholes. On Tue, 18 Oct 2011 12:06:32 -0700 (PDT), bartbrn > wrote: >I'm working on a project that should make LBC purists and hot-rodders >alike gape, gasp, and guffaw: I have one of Bill Bonadio's "Dio" >splashes of the 1959-60 Bill AMes/Dewey BROhaugh AMBRO fiberglass >bodies, originally intended for a Triumph TR-2/3 chassis or whatever >it would fit on (the body will accomodate wheelbases from 88" to 101", >thanks to the trim-able center body pieces), to race in SCCA >"Modified" classes. (If you've never seen one, it is dimensionally and >sculpturally about as close as a couple midwestern racers could get to >a '57 "Knobbly" Lister without generating lawsuits from Brian Lister. > >I'm sending this message to three different user groups: >rec.autos.antique (because of the expertise here on the '64 MGB >running gear I'll be using, and because of the obvious connection to >the wonderful plywood-chassied Marcos cars), rec.aviation.homebuilt, >because I can't think of another group that is likely to have as much >knowledge of stressed-plywood and fiberglass construction, and to >rec.boats.building, because of the wealth of experience there with >plywood and fiberglass craft that don't leak or fall apart in the >middle of the pond. > >I've been trying to get started on this project since I got my >"Dio" (AmBro splash) fiberglass body in 1997 (aahhh, why hurry?), but >miserable interruptions and daunting pre-tasks like actual money- >generating work and my Wreck of the Hesperus garage have kept me in >the "design phase" for 14 years -- during which time some of you may >have even seen a post or two of mine. > >Well, I'm 63, retired, have my garage half-cleaned (my wife's half, >unfortunately...), I've discarded entirely the idea of building up a >steel-tube chassis to drop a small-block into it, and after much >research, doodling, modeling sections, I have come to the conclusion >that the plywood semi-monocoque and 1800cc MGB engine and drive train >are the way to go -- the Marcos GT1800 used (mirabile dictu!) an >1800cc Volvo engine, the same one as in the late, lamented Volvo P1800 >(aside from the PV544, the best-looking car they ever made. But I >digress...) > >I have long had an abiding admiration for Jem Marsh and Frank Costin's >Marcos semi-monocoque plywood-chassis/bodies, especially the GT-1800, >and I found, in Herb Adams' excellent book on chassis design, a >stressed skin "2 box plus integrated monocoque side sills and >bulkheads" design very much like that of the Marcos GT1800. Adams' >design is in steel, and was used for a high-end Cobra replica that >wasn't any more exciting than any other Cobra replica: except that its >stressed-skin-and-bulkhead chassis had HUGE torsional rigidity (as did >the original Marcos and Marcos GT) > >My running gear donor is a '64 MGB-GT that was rotted to within an >inch of its life (so don't fret, "rebuild it from Heritage panels even >if all you have is part of the floor" enthusiasts -- it didn't have >ANY part of the floor (did have some nice sellables, like the aluminum >bonnet, working Smiths heater, several extra 60-spoke wire wheels, >etc.), but for MY purposes, and at $250 for the whole MGB-GT w/ >complete drive train, INCLUDING the 50-mile tow to my garage, it >seemed like the perfect basis, especially as the entire front >suspension and steering rack are mounted to a bolt-on crossmember >(which itself is mounted to the MG's unit body). By using the front >crossmember as a whole unit, all that's necessary is to make sure the >crossmember is mounted to maintain the correct kingpin inclination, as >is perfectly illustrated in the Bentley manual. > >Anyway, that's my double-*******ized sweaty-fingered project of the >decade. If anyone happens to know of a good website that might be able >to help me with the dreary details of this project, please let me know >(I'm thinking plywood boat and experimental aircraft builder's >forums), I'd be most grateful for any links. BTW, the origination of >the Marcos plywood monocoque had a LOT to do with Frank Costin's >previous engineering work at DeHavilland, makers of the plywood >monocoque DH.98 Mosquito "Wooden Wonder" -- the near-"stealth" >invisibility of the plywood Mosquito to "Freya" and various FuG German >radars made it an excellent Pathfinder and Night Fighter. Wonder if it >works against police radar? > >I'm not building this to fool anyone, or to represent it as an actual >original AMBRO (which has been tried, by the most unlikely person one >could think of), it's just going to be a driver. My plan to get it >street licensed by the anal-retentively-regulatory CT DMV is to use >the matching chassis and engine S/N plates, and call it an "MG >Special," like the Lester-MG. Will it work? At 63, will I live long >enough to complete it? Who knows, but as my distant -- VERY distant -- >relative Robert Browning said: "Ah, but a man's reach should exceed >his grasp, or what's a heaven for?” > >Sorry for the long post. If anyone's interested, I'll be putting up >pix of the project elements, design, and build on Photobucket or >FlickR. > >Any suggestions -- other than "get thee to a loony bin" or "go soak >your head" gratefully accepted. > >Peace > >Bart Brown |
#3
|
|||
|
|||
Plywood chassis bonded to 'glass body (think "Marcos GT1800") project
Thanks for the very welcome advice -- I'm going to do it pretty much
just like Marcos did it, although I'm not sure if I want to go to the expense of marine plywood as they did: they used marine ply primarily because the glue between laminations is not supposed to have ANY gaps (I don't know how you'd tell, non-destructively, except by X-Ray). Anyway, to make up for the rigidity lost by having an open cockpit, Marcos used a triangular boxed sill of ply, glued at every joint with 1" x 1" spruce corner bracing, and epoxy-glassed to the fiberglass body's undersill. I'm doing the same, except my sills are much deeper (the Marcos' were about 5"-6") separate fiberglass panels with a regular and continuous 10" radius under-curve. The main top fiberglass body pieces continue this 10" curve radius, so, without offsetting the flooring up or down, the body is 20" deep at the cowl. The rear body panel is about 4" higher, but still connects as a smaller bulkhead to the undersill). The other main strength of the Marcos cockpit was a very deep central drive tunnel that connected front and rear bulkheads of spruce- reinforced ply. Mine will be similar, with a central drive tunnel of the same 10" height as the side sills, and tied into epoxy glass and ply -- not just ply -- cowl bulkheads immediately fore-and aft of the cockpit opening. There will be latitudinal enforcements, epoxy-glassed inside each side sill. Three of the enforcements will be continuous from sill to sill across the cockpit: one at the rear bulkhead, the next under the driver's knee position (like in a Porsche 550 Spyder), and finally the front cowl bulkhead -- these epoxy-glassed ply enforcements will tie the left and right sills, central tunnel, and fore and aft cockpit bulkheads together, more than making up for any loss of torsional rigidity from the "big hole in the middle" cockpit. The two sides of the drive train tunnel angle open as the tunnel goes forward through the front bulkhead, to accomodate the engine and transmission, and, with the footwells, the outer sides of which are an un-jointed continuation of the inboard cockpit interior sides of the boxed-in sills, will also be boxed and angled to provide steering clearance for the front wheels, and provide a multi-laminate fore- and aft-braced connecting point for the front MG cross member. In front of the MG cross member, there will be another glass and ply bulkhead that will provide additional stiffness for the engine bay, and separate the engine entirely from the radiator, which will be angled and mounted forward, along with the 13-row Serck oil cooler, in a closed extractor tunnel that will take advantage of the low-pressure area produced by letting a radiator air exit into the "knobbly-style" center hump of the bonnet, the low pressure area helping to pull air through the oil and water heat exchangers. For low speeds and idle, a thermo-coupled 12" electric "sucker" fan will be mounted just behind the radiator. From the rear cockpit bulkhead back there will be "stressed skin" ply, spruce reinforcement, and epoxy glass torsion boxes. Immediately behind the cockpit will be the fuel tank, and for the rest, I'm keeping the leaf springs and Armstrong lever shocks, the attachment points of which to the ply torsion boxes will be reinforced on both sides by 1/8" steel load-spreading pads. The only change to the rear suspension will be a polyurethane-bushed straight pivot (i.e., not a "rose" or "Heim" joint) welded steel "A" arm, each "leg" of which will mount to the torsion box in vertical and horizontal alignment with the left and right front leaf spring-eye mounts. The apex of the fabricated "A" will converge on another urethane-bushed straight pivot, confining rotation to 90° to the car's centerline, which will attach to another weldment tied into the top of the differential. This fabricated "A," thus mounted, will control lateral axle movement better than the leaf springs alone, and will also prevent axle "wind- up", both in acceleration (which will hardly be neck-snapping with a pretty bog-stock MG 1800) and braking, which will have to be carefully set-up, taking into account the considerable weight reduction, and the single-puck stock Girling front brakes. All exposed ply surfaces -- like the woven-glass-and-epoxy-sealed 3/4" plywood floor (also tied into all torsion boxes and sills with which it comes in contact) -- will be sealed and painted with Valspar. Sorry for the long explanation, but I was writing this out also as a plan to which *I* can refer when I get lost! Thanks for your interest! Bart On Oct 18, 5:22*pm, wrote: > There shouldn't be anything too difficult or dangerous about what > you're describing. *Pick your plywood carefully oak might be one > choice, unless you run across something else, and select the > fasteners/fastening system carefully. *You'll want some "give" to the > system, so it doesn't self-destruct over a few potholes. * |
#4
|
|||
|
|||
Plywood chassis bonded to 'glass body (think "Marcos GT1800")project
On 10/19/2011 12:50 AM, bartbrn wrote:
> Thanks for the very welcome advice -- I'm going to do it pretty much > just like Marcos did it, although I'm not sure if I want to go to the > expense of marine plywood as they did: they used marine ply primarily > because the glue between laminations is not supposed to have ANY gaps > (I don't know how you'd tell, non-destructively, except by X-Ray). I used some marine plywood for a project years ago because I was told it has no voids (IE. empty knotholes in the plys). I did not encounter any in the couple of pieces I used. Furniture grade plywood, on the other hand, has a number of interior voids. I've used lots of sheets and they have all been that way. That is not necessarily a strength issue in furniture, but you do have to be careful with screw placement. Construction grade plywood also has plenty of voids. Good luck with your project. Mike |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
"Life Hammer" for breaking window glass too flimsy? | Jonathan Kamens | General | 22 | August 25th 08 12:06 AM |
Understanding "recycled" chassis drivetrains | Josh[_6_] | Technology | 4 | February 27th 08 07:56 PM |
dax rush hayabusa turbo [87 of 151] "Fuurin (Glass Wind Chime).gif" yEnc (1/1) | Wim Zomer | Auto Photos | 0 | February 9th 08 12:30 AM |
FS- 1971 Ghia Coupe "project" in Gainesville FL (262 800x600 pixonline at site) | dave | VW air cooled | 0 | February 17th 06 08:23 PM |