Author Topic: cast aliminium bash plate (Read 15608 times)

Sláinte Mhaith · « **Reply #20 on:** May 24, 2015, 09:33:14 am »

Quote from: RobC on May 23, 2015, 12:01:57 pm

No! Do not diy a cast one...
Cast aluminuim does not have the tensile strenght plate has.
The metalurgists on the group will explain why.

From the little I learned and the less I know now (not a metallurgist either by a long shot)

Casting will have a granular structure while wrought plate will have a long grained structure.
In my mind it is like gluing lots of small balls together vs gluing small sticks together. You can imagine how the sticks will be stronger.
Similar to cast iron vs steel the first will be brittle.

So my guess is a cast bash plate will most likely crack and/or break instead of deforming.

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Welsh · « **Reply #21 on:** May 24, 2015, 12:30:33 pm »

Pressed, fabricated or forged, if cast was strong enough you would not need a bash plate as cast cases would be strong enough. It's about elongation before it breaks.

2StrokeDan · « **Reply #22 on:** May 24, 2015, 06:08:50 pm »

Quote from: Welsh on May 24, 2015, 12:30:33 pm

Pressed, fabricated or forged, if cast was strong enough you would not need a bash plate as cast cases would be strong enough. It's about elongation before it breaks.

A lot of alluminium alloy frames has cast joints and steering head pieces in them, of course these are substantial in thickness.

adamktm · « **Reply #23 on:** May 24, 2015, 07:46:18 pm »

Looking forward to seeing how it turns out!!

shanti · « **Reply #24 on:** May 24, 2015, 09:10:05 pm »

will post some pics as it goes , I'm going with the good deflection due to rounded shape and figuring a casting of 5mm is bound to be strong enough + soft enough to absorb/protect from rocks etc , I might be wrong - how the hell do you do a strength check ?

Gerrard · « **Reply #25 on:** May 25, 2015, 08:43:08 am »

Quote from: shanti on May 24, 2015, 09:10:05 pm

will post some pics as it goes , I'm going with the good deflection due to rounded shape and figuring a casting of 5mm is bound to be strong enough + soft enough to absorb/protect from rocks etc , I might be wrong - how the hell do you do a strength check ?

Remember Thomas Edison, and how many times he tried, and failed, before he got the light bulb to work. If he did not try and fail we would not have had lights.

Make a rough tester and moer it with a 5pd hammer. Remember, impact that is not absorbed, is transferred somewhere else.

lecap · « **Reply #26 on:** May 25, 2015, 12:41:40 pm »

Quote from: Welsh on May 24, 2015, 12:30:33 pm

Pressed, fabricated or forged, if cast was strong enough you would not need a bash plate as cast cases would be strong enough. It's about elongation before it breaks.

In parts like cast frame members or swing arms you have well defined forces below the yield strength of the material.

Most impacts into the sump guard cause forces well in excess of the materials yield strength. You need a material which is ductile on the one side (it absorbs energy by deforming and allows a high amount of elongation before it tears) and has good shear strength on the other side (a rock will not tear a triangle shaped hole).
I found sump guards from 4mm 5083 sheet to work very well and the sheet is readily available and quite corrosion resistant.
The putty soft architectural grade stuff is useless.

A cast bash plate will crack and shatter just like eth engine you are trying to protect.

shanti · « **Reply #27 on:** May 25, 2015, 01:19:38 pm »

day is moving along slowly - against all logic (even my own after doing some reading and reading the replies) decided to give it a go , started my day with some urgent sculpture work ( gotta get paid for messing around ) now busy with the mould should have something cast at the end of the day to beat up with some hammers

the_BOBNOB · « **Reply #28 on:** May 25, 2015, 01:32:11 pm »

looking good

i'd like to see the end product, i think it will work

you can also add some fibreglass on the inside of the when its done - that should enforce it - in the end if it cracks it did its job - it protect your casing

if something hits it that hard that it can punch through it, through some fibreglass or rubber enforcing and then still break your casing you are screwed anyway

Titanic · « **Reply #29 on:** May 25, 2015, 01:38:24 pm »

Shanti
Sorry for hi-jack.
When you are done with this project, why don't you have a look at the following? It might be easy for you to make us something similar.
Mirror/choke relocation bracket for the KLR
http://www.eaglemike.com/Choke-and-mirror-relocation-bracket-cmrb.htm

growweblaar · « **Reply #30 on:** May 25, 2015, 01:47:27 pm »

Interesting experiment! Subscribe.

I suspect it will shatter if you hit a rock hard, but perhaps fine otherwise...?

Have a look at this table comparing different alu alloys, magnesium, zinc & cast iron for casting. Yours would be in the S/SM column, since you're sand casting.

shanti · « **Reply #31 on:** May 25, 2015, 05:52:08 pm »

cast the plate - last cast for the day , foundry work is hardest on Mondaze for everyone - will take a look tomorrow better - although I couldnt resist swinging a hammer at it - slight dent but cant trust that as a test for a 50km wack - still figuring deflection is this plates strength - thanks for that table - would be interesting to see what the heattr is ( heat treatment ? ) I will consider casting smaller items Titanic - I am an artist so dont have much in the way of machining in my workshop . I think for the finer items perhaps doing a lost wax casting might be better - i get good results with my bronzes with very small tolerances , can pick up a finger print in the wax if I pay attention - of course there is always shrinkage to be accounted for - will carry on tomorrow

shanti · « **Reply #32 on:** May 25, 2015, 05:55:15 pm »

I did modify the original plastic bashguard by removing the lower holes and adding a strengthening to the base , those familiar with the plastic bashguard will notice the difference

Welsh · « **Reply #33 on:** May 25, 2015, 06:01:19 pm »

Impressive... really cool

Sláinte Mhaith · « **Reply #34 on:** May 25, 2015, 06:40:08 pm »

Quote from: Welsh on May 25, 2015, 06:01:19 pm

Impressive... really cool

+1

Crab · « **Reply #35 on:** May 25, 2015, 07:26:05 pm »

Looks good so far

Weedkiller - Adie · « **Reply #36 on:** May 25, 2015, 08:01:50 pm »

Bliksem
so leer ons elke dag iets nuut

Adie

zacapa · « **Reply #37 on:** May 25, 2015, 08:23:01 pm »

nice thread with some counter intuitive angles. then again I bought an XR650L which is so high off the ground there is little need for a bashplate in the first place.

capeklr · « **Reply #38 on:** May 25, 2015, 08:51:32 pm »

I like, I see it comes complete with centre stand.

shanti · « **Reply #39 on:** May 25, 2015, 08:54:26 pm »

havn't you seen the aquaplaning farkle for the KLR yet ?