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MG Midget and Sprite Technical dont hate me,,, BBS discussion at MG-Cars.net
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MG Midget and Sprite Technical - dont hate me,,,
| Im toying with the idea of lambo style doors, rotating up 130 degrees! I think it would mean modifying the a-post area by removing the original a-post and re-strengthening in the same position, inside the footwell. The door skin or wing would then need extending to brige the gap left by the a-post skin. I think this would look awesome! Obviously modifying the structual parts of the is a little risky, but as long as i replace the structural bits with same or greater strength material, it should work, right?! Tube or box section just on the inside of the footwell side wall, oposite the a-post should be enough i would have thougt, and maybe a diagonal brace through the sidewall to the top of the sill... any thoughts? remeber, dont hate me, i havent done it yet! |
| Rob McGeown |
| Hi Rob Have you tried a Lambo with these doors? Are you making a design statement or making your car easier to get in/out? A |
| Anthony Cutler |
| oh its purely a design statement, no need other than that. I guess it could help getting in and out in my tiny garage! |
| Rob McGeown |
| I'd imagine that it would add a lot of weight, unless you were using fibreglass doors. Is it going to worh with a soft/hardtop in place? Why not a dropping door like the BMW Z1. Much better I'd say and also stronger. |
| G Lazarus |
| The hinges would be the only additional weight, but they do not need to be as heavy as the doors a reasonably light.. |
| Rob McGeown |
| B & Q do some concertina shower screen doors that could be cut down to fit. Not quite the look you were after? |
| Guy Weller |
| How about some nice pine louvre saloon type doors. Now we're talking class. |
| G Lazarus |
| thanks for giving this your serious consideration! Just the technical opinions i was after! :) |
| Rob McGeown |
| http://cgi.ebay.co.uk/NEW-TURBOREVS-UNIVERSAL-LAMBO-DOORS-KIT-DOOR-HINGES_W0QQitemZ380082560970QQcmdZViewItemQQptZUK_CarsParts_Vehicles_CarParts_SM?hash=item380082560970&_trksid=p3286.c0.m14&_trkparms=72%3A1301%7C66%3A2%7C65%3A12%7C39%3A2%7C240%3A1318 |
| G Lazarus |
| id seen those ones a few moments ago, look quite cheap for UK made ones. The US ones come in cheaper, but shipping add on. What are thoughts about moving the a-post inside the footwell? |
| Rob McGeown |
| This issue I see is that the midget door opening is too short. So a door rotated vertically around the front a-post (or even with the a-post moved forward) simply wont give you the required opening to get out. I'm "of average height" ;-) and dont think I could get in/out with and less door opening than now. |
| Dean Smith ('73 RWA) |
| The door opens normally for a while, then stops, then rotates up. This give clearance for both the screen and the wings etc The pic shows a set of hinges, the top hing does the outward rotation and the round hinge does the upward rotation. I would completey remove the a-post in its current location and replace it with reinforcement on the inside of the footwell, as the door wont hinge of it anymore.  |
| Rob McGeown |
| As an engineering excercise and for novelty value it would be fun to see the system installed on a Spridget. I'm warming to the idea. |
| G Lazarus |
| But for the waistbandedly? challenged, long limbed amongst us the door is a useful thing to grab on to whilst trying to get out with the roof on! It's either that or plant two hands on the road and go out head first which is becoming less dignified the portlier one becomes! |
| Matt 1275 Bucks |
| Don't worry Rob, we won't hate you. We'll probably laugh at you, but we wouldn't hate you... |
| Tarquin |
| the more i think about it, there more i want to install it. once that a-[post is out of the way, it just bolts on (once correvtly aligned of course)! |
| Rob McGeown |
| Ok, ive consultate a couple of companys who fit these hignes to most road cars. They have just made hinge to fit the classic mini, and say it is completely different to any other one they fit. They also say you need at least 4 inches between the mounting point and the wing, which the midget clearly doesnt. So im designing my own! The door will not swing open in the conventinal manner, as the current lambo hinges do. It will effectively open parralel, with some forward motion. This will enable the door to be completely clear of the entire body and it will then rotate vertically. Its a lot of work, and im just bashing out ideas at the moment, im going to take measurements tomorrow and physically look at the idea. The attached pics are of the initial hinge design, im looking at it in two parts. The hinge, and the pivot. The pivot will be attached to the door, rather than the hinge. This part only moves the door out of the door opening, it does not rotate the door vertically. Any thoughts? Oh and just to be safe Copyright Rob McGeown 2008!  |
| Rob McGeown |
| Rob, An initial thought is you need another link of the same centre distance but offset from and parallel to the centre link in order to constrain the end links to move parallel to one another. When all 3 parts are aligned the centres will fall in a straight line, when opened the centre links will form a parallelogram. |
| David Billington |
| Sorry Dave you've lost me there... |
| Rob McGeown |
| if i understand you correctly, would the gas strut no have the same effect? |
| Rob McGeown |
| Rob, The gas strut varies in length according to load so won't provide the constraint required. Have a look here for an example of the type of link I think you want for parallel opening action http://www.technologystudent.com/cams/eglinks2.htm . Can draw if required but not this evening, it's late. |
| David Billington |
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| Jordan Gibson |
| Rob, You cant live by what others think, the midget is an extension as to who YOU are, not me ...prop, or even Arie (yeah we all want to live in aries world, or is that just me...LOL) If this is something you want, then you should absolutly do it. As to my opinion, I really hope you do it, cause I want to see this, I have to admit, I have given this some thought myself, and the idea is appealing to me as well. I wonder instead of modifying the A post, why not make the door a "suicide lamdo door", that way you wont have to modify the door post, you could use a magnetic lock, instead of a clip and bolt type system anyway, I hope you do it prop |
| Prop |
| how about a couple of springs in place of the gas strut? Under tension when door is closed, untensioned when the hinge is opened. Would they effectively pull the link parallel? |
| Rob McGeown |
| Rob, To produce a parallel motion you want something like my LowTechLamboDoor (tm) for Morris Minor travellers, this one in pine, final would be ash. Pen marks indicate pivot axes. Also https://www.streetridepro.com/techzone/lambo_install_instructions.pdf Shows that unit seems to have a single pivot rather than parallel motion and an installer who can't weld. |
| David Billington |
Images help.
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| David Billington |
and
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| David Billington |
| ah i see, thanks for that! I now understand that the door would actually pivot normally without that! im in the garage all day today, and looking at the door/footwell im sure i can do this. The rotational pivot would actually be inside the door, and the parallel pivout on the footwell wall... more designs to come tonight! Having said that ive just bought 1000W of halogen site lights, so i may stay out late! |
| Rob McGeown |
| Rob, I wonder if you might be able to use one like that shown in the PDF file I posted before. As I understand the action it allows the door to open normally a small way to clear the catch then pivot upwards. If you had the pivot somewhere near the back upper corner of the footwell you might be able to organise the necessary clearances with the A post by creating a tunnel through it for the upwards swinging arm. The single pivot vertical axis pivot allows the door to to be pulled shut normally as I see it. Using a parallel action might create an issue with pulling the door closed in the normal way. |
| David Billington |
| That was the initial thought, but on speaking with a company who installs them, they were convinced they needed at least 4inches clearance. |
| Rob McGeown |
| Rob, Guess you'll just have to ponder the options and find a workable solution or prove them wrong. I can see you might be on the look out for a section of the side of beyond worthwhile repair midget and door to play with so you can mock up options before altering your car. |
| David Billington |
| Ok here's V2... the parallel restraints as per Daves advice. recessed area for the gas strut to cope with the angle. 30mm sealed bearing unit and the shaft that will mount inside the door... Basically most of the left block will be inside the door...  |
| Rob McGeown |
| Rob, While the images I posted earlier show the idea of the parallel linkage I think a practical version for your requirement would need more than just the upper and lower links you show to provide the rigidity in the parallel link motion, at the moment it would be easy to twist with just the 2 links. Also in order to swivel the door upright and beyond you would need a cutout or upward bending dogleg in the bracket at the lefthand end I think as otherwise the door front edge will foul the hinge when raised. See bad image showing cutout, dogleg much better I think. What are you using to model the images. I have 2D and 3D drafting packages but am not proficient enough to spend my time drawing unless I require it. I use mostly the 2D for DXF files for laser profiling and the like and that is easy. The 3D comes in useful for intersections of shapes but I don't do it often enough and so it's a bit of a learning curve/remembering each time. I wonder if these might give you any ideas http://www.soss.com/ also US patent 7140075 , I haven't got the TIFF viewer on my current system so couldn't look at the images.  |
| David Billington |
| im just using google sketch, its basic but it seems to work. It would take me ages to learn a true CAD system i think. Im not sure about the dog-leg/cutout, its difficult to explain how i imagine it working... The door would sit a little higher than the left most plate, on the bearing. The door would be attached on the bottom right of the door. The parallel hinge would pull the door so it is clear of the body work, the it would rotate on the bearing until it hit a stop block or similar. Although it would only pivot around the bearing at the bottom right, there would be a bracket that attaches to both the door's hinge plates to support it. I agree the links need to be more substancial, possibly three links, or much larger links... another few designs to come, possible a wood mock up tomorrow! |
| Rob McGeown |
| Rob, I was only thinking that if the pin the door pivots on is within or partly within the door then with that pin being fitted to a straight horizontal plate the door will foul when raised towards 90 degrees. Maybe a sketch with some door references included would help. |
| David Billington |
| looking at it again your right! The pivot would need to be inside the top right of the door and there would need to be a cutout in the plate! This sketch makes it clearer. Each one is an improvement, might eventually get a useable design!  |
| Rob McGeown |
OK now its getting complicated!
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| Rob McGeown |
and here it is rotated...
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| Rob McGeown |
half open...
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| Rob McGeown |
fully open, rotation and parallel action:
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| Rob McGeown |
| Rob, Google sketch is an excellent program for quickie pics, you could probably fabricate & fit the hinges in the time it takes to learn CAD. |
| Brad (Sprite IV 1380) |
here's a scale model, may need further revisions...
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| Rob McGeown |
| Wow, Now that is over the top (yeah its a pun), your definatly going to need some locating pins, for the door to lock into place, Im not so sure I wouldnt put the hinge on the opisite side of the door, for better access, and struturle strenght, and alignment into a locating pins,,,,aka the post behind the seat. truly fasinating prop |
| Prop |
| Rob, Looks likes it's coming along nicely. Do you ever find yourself waking up in the morning thinking 'must just check that ????' ?. |
| David Billington |
| all the time. |
| Rob McGeown |
| dont worry, Thats not a problem till you start waking up at 2AM thinking about it, and cant go back to sleep....god I hate that...why is that? The best ideas always come betten 2am and 5am.....almost never at 3pm prop |
| Prop |
This thread was discussed between 27/11/2008 and 02/12/2008
MG Midget and Sprite Technical index
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