Ray_li

I have two engineering questions that I need help with.

1st question.

How do you mechanically convert a vertical movement in to a horizontal movement? Eg. a horizontally mounted suspension that is connected to a wheel that moves vertically.

2nd question

How do you stop a 700mmX60mmX10mm (10mm is thickness. Could be a little bit more thick) block of aluminium or steel from bending and flexing. I need this very stiff without any movement.
Iv been told bolting two plates together would do the job. Does this need to be different metals? or having square tubes bolted to the top and bottom of it.

any answers would be very grateful.

Ray

LanciaChris

1. Crankshaft!
2. No idea

Mufasa

Q1

Bellcrank

Q2

Usual way to stiffen a plate up is to mount another plate on it, on it's edge. Like a bit of angle iron.

Sturge

Only way to convert vertical to horizontal is using rotational movement, so a bellcrank of some description, solid link to a rocker, other end attached to the horizontal moving part. Lots of different designs are out there, majority of single seat racing cars use this sort of set up.

Depends what the plate is for, direction the stiffness is required, how it's loaded etc.

Ray_li

I still cant get my head round question 1. the bellcrank is a really good example. Does anybody have any more examples like that.

The plate is to mount some realy sensative reading equipment that needs to be dead still. The max load would be around 1.5kg or less and its will be exposed to heat so i dont want heat bending it.
Im currently using a 25mm think aluminium plate (700x60x25mm) and that it huge and heavey. I need the same stiffness but using less material.
Thanks

Ray

Sturge

Think a bellcrank of some description is the only way i'm afraid mate, or some variation of it.

Angled gussets either end and diagonal strengthening ribs would do it i think(kinda like u get on the bottom of plastic storage boxes or bread crates)

Katana

Final year project eh? Damn you've just reminded me to start on mine.

As for stiffness, why not increase the depth of the steel/ali by using 2 plates instead of one like a strut?

Sturge

nah, got year in industry before i worry bout that lol

2 plates would mean lots of extra weight, said he was wanting to cut that down

midget1500

weren't you designing gatso's now? folks - don't help him

beemerboy

use a pcb...

BB

Ray_li

Extra plate will not do the job, need to cut down on weight. was thinking about casting a block with webbing on the back for stiffness but I dont think you can mill it perfectly flat and drill at 90 degrees.

beemerboy

LOL. they gonna train me up to design simple pcb's now from someone that knows bugger all about electronics.

Leslie

Make the bell crank device up like a space frame with triangulation of the struts to get max stiffness with minimum weight. You need a double pivot for the input from the bell crank to the measuring device to get a parallel motion with a sliding bearing for the final input to the instrument.

Les

Pavlo

Use a bellcrank, connecting rod and parallel lingake to get the motion sorted, basically the same system that was employed in the first widespread steam engines. There is a specific name for the linkage, and it's designed to overcome your specific problem, initially to get drive from a piston without putting a side load on it.

For the plate, if you want the stiffness without weight, get some alumnium honeycomb, you can buy it 25mm thick made with 2 1mm skins. It's about 50% of the stiffness of solid 25mm plate, but about 5% of the weight, get it in 40mm thickness and it will be stiffer than the solid plate. If you can't get any, then I would suggest 2 1.6mm alumnium strips epoxy bonded to a peice of closed cell foam, or balsa wood. If you can find the right extrusion, then a peice of extruded box section aluminium may also be suitable, but without knowing what you want to do exactly it's hard to pick the best option.


Remember that stiffness is proportional to the thickness cubed, so a less dense material but with equal stiffness to weight ratio will always result in a stiffer beam mass for mass.

Paul

hades

The honeycomb / ultra lightweight material sandwiched between thin sheets of something is definitely the way to go for light & stiff. I have found some immensely stiff and lightweight plates by getting aliminium honeycomb with thin carbon fibre sheet on either side of it. Many model aircraft wings are light and suprisingly stiff by just having polystyrene sandwiched in thin plywood.

Ray_li

hades

Is honeycomb expensive. I dont think i can use stuff that cost loads and do you guys know where I can get some from?

Ray

ps Thanks to everybody thats helped answering my questions, its my first design job and Im still trying to impress.

pslewis

2. Use Webs along the length to lend strength, if I understand the question properly?

1. Round gear wheel to a flat bed of gear teeth

Just a couple of suggestions

Pete

Ray_li

Bellcrank is along the lines but without the extra movement (the arch movement) just the two (horizontal and vertical)
Keep them coming

thanks guys

Ray

[Edited by Ray_li - 8/9/2003 6:02:15 PM]

Ray_li

Pavlo

Great info there mate, but i cant picture the bellcrank with the links. It sound along the lines of what I am looking for.

I think bonding two plates of aluminnium together is the best option. Why bond it to foam or wood and is that arange like a sandwich with the wood or foam in the middle?

Ray

[Edited by Ray_li - 8/10/2003 2:11:00 PM]