 Rotiserie, The rear mount |
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| cwpeden |
 Feb 21 2011, 12:47 AM
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#1
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Great White North, huh?  Group: Members Posts: 916 Joined: 20-August 06 From: Victoria BC Member No.: 6,693 Region Association: Canada  |
So I've finished my rotiserie and after mounting the rear bar to the bumper holes, the whole rear looks a little 'flexy'! I can grab the bar and move it up and down easily.
Did those of you who used the bumper holes reinforce anything? I built it according to drawings and advice on this forum. Conrad. |
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Replies(1 - 13)
| Richard Casto |
Feb 21 2011, 06:53 AM
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#2
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Blue Sky Motorsports, LLC Group: Members Posts: 1,465 Joined: 2-August 05 From: Durham, NC Member No.: 4,523 Region Association: South East States |
My first thought is that your rear bumper mounts might have some structural issues.
Post some photos. |
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| Dr Evil |
Feb 21 2011, 07:12 AM
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#3
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Send me your transmission! Group: Members Posts: 23,034 Joined: 21-November 03 From: Loveland, OH 45140 Member No.: 1,372 Region Association: MidAtlantic Region 
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Is your car stripped of engine, tranny, suspension, interior?
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| PanelBilly |
Feb 21 2011, 08:56 AM
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#4
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914 Guru Group: Members Posts: 5,864 Joined: 23-July 06 From: Kent, Wa Member No.: 6,488 Region Association: Pacific Northwest
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I used some 10" long bolts in mine so I had room to work and paint the area right around the holes. Even with the extended connection, there wasn't any real flex. I'm thinking you have issues with the rear panel
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| r_towle |
Feb 21 2011, 11:55 AM
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#5
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Custom Member Group: Members Posts: 24,663 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States
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post a pic of the bar attached...
RIch |
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| IronHillRestorations |
Feb 21 2011, 12:09 PM
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#6
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I. I. R. C. Group: Members Posts: 6,792 Joined: 18-March 03 From: West TN Member No.: 439 Region Association: None
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I've always thought about making some extentions that would bolt to the transmisson mounting points for cars with rusty trunks.
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| Gudhjem |
Feb 21 2011, 04:19 PM
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#7
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Member Group: Members Posts: 133 Joined: 29-March 07 From: Castro Valley, CA Member No.: 7,629 Region Association: Northern California |
QUOTE(cwpeden @ Feb 20 2011, 10:47 PM)  So I've finished my rotiserie and after mounting the rear bar to the bumper holes, the whole rear looks a little 'flexy'! I can grab the bar and move it up and down easily. Did those of you who used the bumper holes reinforce anything? I built it according to drawings and advice on this forum. Conrad. Mine feels solid; no flex. I used the plans at Roadglue. It's not just sheetmetal at the bumper mounts. There should be a reinforcing bracket of sorts where to bolts go through, both front and back bumpers (there is on a '73 anyway). Also, I suggest using fender washers where you bolt to the car to help distribute the load a bit better. |
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| cwpeden |
Feb 21 2011, 07:33 PM
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#8
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Great White North, huh? Group: Members Posts: 916 Joined: 20-August 06 From: Victoria BC Member No.: 6,693 Region Association: Canada |
I used the plans off RoadGlue also. There was a link in the forums here.
The only thing left in the car is the harness and a few small parts. There doesnt appear to be a significant amout of rust. Just the usual. I could flex the mount before I put it up on the stands. I think I'll just empty the body out completely and keep an eye on it as I work. Maybe tack a couple of braces inside the trunk and fenderwell.   |
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| r_towle |
Feb 21 2011, 07:40 PM
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#9
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Custom Member Group: Members Posts: 24,663 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States
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Looks like the bolts are a smaller diameter than that tubing you are using...so there is some flex.
Also, if it was me, I would cut the tubes shorter to get closer to the body. I would also add a single steel plate to the ends of the tubes to ties them together at the body...then bolt through all of that. You are putting more stress on the whole setup the farther away from the body that you make that square tube.... Get as close as you can with the square tube... You can work on that rear panel after you remove the bracket and its on the jack stands again. Rich |
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| scotty b |
Feb 21 2011, 07:46 PM
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#10
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rust free you say ? Group: Members Posts: 16,375 Joined: 7-January 05 From: richmond, Va. Member No.: 3,419 Region Association: None |
Make a plate with the holes in it to put on the outside. Run your bolts through that plate. This will distribute the load across a larger area. Also put some ;arger fender washers on the back side, for the same reason. right now you have the full weight of the car supported by a VERY small diameterof sheet metal around the holes
I am temporarily using the bumper holes to gte a job done. The next step in my rot is just what Perry said. I will be using the trans mount as the main pickup point for the rot. and from there I can tie the rear suspension in, followed by a framework under the floors. Then the front suspension can be tied into that and also be the front mount. This in effect ties the front and rear suspension together, and allows for removable posts for the rear suspension mounts. All this is to avoid the rear end sag caused the inner AND outer longs are cut out. Pics will come when I get to that point |
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| Richard Casto |
Feb 21 2011, 08:18 PM
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#11
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Blue Sky Motorsports, LLC Group: Members Posts: 1,465 Joined: 2-August 05 From: Durham, NC Member No.: 4,523 Region Association: South East States |
A few quick random thoughts...
The plans that were on Roadglue were mine. As Roadglue is down for good and the wiki is eventually going to be back up here, those plans should show up here in the future. I may host the plans again on my site if that conversion takes a long time. Everyone may not build exactly to my plans (and that is OK). The tubes I used to offset were pretty thick. I also offset them as much as I did so that work (including media blasting, etc.) could be easily done. I have no doubt that the design is fine with respect to the strength of those tubes at the length I have them. I am sure they are stronger than the box section they are welded to. I like the idea of putting fender washers on both sides of the sheet metal (or plate on outside and fender washers on inside, but I think fender washers on both is easier). It should increase the "clamping area" and would reduce the risk of damage. Especially to the top holes (see comments below). Also I don't think the smaller bolt diameter is an issue as in my opinion the bolts are not used to "position" but rather "clamp". It is the clamping force that keeps the entire bar positioned on the car. The bolts just need to be large enough to safely provide enough clamping force. The structure on the car for the rear bumper mounts is a joke compared to the front bumper mounts. On the rear you have a small angle reinforcement that ties to the trunk floor, but only for the lower mount. The top mount is just a hole in the thin sheet metal with no other support. The front bumper has a significant angle piece that supports both top and bottom mount locations. I don't know what early 1970's crash testing was like, but I assume the front had to meet some level of crash tests while the rear on the other hand must have had much less severe requirements. My trunk has way more "swiss cheese" going on than yours. Mine has been on the rotisserie for a long time. So I can't remember exactly how much flex it had when unmounted. When on the frame, I can't seem to get it to flex at all. Maybe as it is fixed along a rotational axis now it can't easily flex as much as it might have when not on the rotisserie frame. If there is any flex, I would guess it would be around the unsupported (see comment above) top mounting holes. Good luck and I hope it works out for you! Richard |
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| cwpeden |
Feb 22 2011, 02:03 AM
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#12
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Great White North, huh? Group: Members Posts: 916 Joined: 20-August 06 From: Victoria BC Member No.: 6,693 Region Association: Canada |
Cant make the tubes shorter, have to clear tow eye mount.
Picked up some 2 inch flat bar to go between the ends of the tube. Stay tuned..... |
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| Haudiosolutions |
Feb 22 2011, 06:49 AM
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#13
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Member Group: Members Posts: 215 Joined: 19-October 10 From: Sevierville, TN Member No.: 12,284 Region Association: South East States |
I'm about to start this portion of my project. Those plans would be handy if someone has them.
Thanks in advance Derrick |
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| arkitect |
Feb 22 2011, 09:33 PM
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#14
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Senior Member Group: Members Posts: 617 Joined: 3-March 10 From: Stockton, CA Member No.: 11,426 Region Association: None |
How much length do you have to add to make a engine stand high enough to make the full turn? 12"?
Dave |
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