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I have now been able to move this project forward.
I will be selling these through Roger at 928'srus as sponsorship was relatively expensive for a small run (10) of this type. Neither He nor I am making any money out of them at this stage. Cost is likely to be in the US$210- $220 range plus shipping from Roger. (Depends on actual freight and exchange rate).
The parts will be sand cast from a LM25 alloy (blurb below) and black powder coated.
We will see how demand goes. I can get additional runs of 5 or 10 (or more) produced relatively cost effectively as the main setup costs allow for around 50 parts before needing to be repeated.
At this stage I am getting a couple of units made so I can confirm fit (in case any of the thickening / strengthening I have got built in needs reducing) and durability / strength and finish. I will post pictures once they are to hand.
Myles
"LM25"
L M 25 is an aluminium alloy that conforms to BS 1490 and is particularly suitable for use in high quality castings where strength, definition and good corrosion resistance is important. Alloys with similar chemical composition are used throughout the world, see below for details.
Application
LM 25 is a high purity aluminium alloy, which can be gravity diecast in permanent moulds or sand. It has excellent castability and good mechanical properties that can be varied by heat treatment. The alloy is mostly used for high specification castings in industries where shape and complex form is required and casting soundness is important. Its use is widespread in the automotive industries for alloy wheels, cylinder heads and blocks and in many other industries such as chemical, marine and electrical.
Castings made from this alloy can be supplied in the as cast form or in one of three other heat treated conditions.
It should be noted that there is no significant advantage to be gained from heat treatment if the service conditions envisaged are likely to include extended periods at temperatures above 130°C. However, hardness, tensile strength and elongation can be significantly improved by heat treatment. Castings in this can be supplied in the M, TE, TB 7 and TF conditions.
This alloy has excellent resistance to seawater attack and can be anodised to improve its corrosion resistance. Anodising will give a grey / opaque finish suitable for dark decorative finishes only. LM 25 also has good machining characteristics and can be welded if required.
I believe the originals were pressure cast, which makes them much stronger. Gravity cast is the weakest method to use. I would suggest heat treatment after casting as this will help.
I know money is hard to come by,oh do i know. However if you could find someone (hum like Roger ) to help with the up front i am sure of one thing,over time they would all be sold. Best to you for your effort,Ray
Hi all - an update:
After much time and effort (& money) we have come to a dead end on this. While the engineering firm was able to get a silicon mould of the part made they have not been successful in getting an intact wax mould out of it.
I will keep looking for alternative production methods but at this stage the remaining production options would appear to be very expensive for a short run, consisting of $5K - $10K setup costs which would mean I would need to sell 50 to 100 of these to recoup costs.
Unless anyone out there has any bright ideas it seems like unlikely this project will be able to proceed.
Myles, first I am puzzled about the reference to wax. Your earlier posts state that you are going to have these sand cast; and wax does not play a part in that process, that I know of.
I too have been working on a project like this but utilizing an investment casting process that does involve wax duplicates. I am on the cusp of having those developed, but even that cusp is some ways away from actual duplicates. Right now I am working on the difference between making a mold for the waxes and having the waxes 3D printed. I don't know too much about the difference in cost.
I have the facilities to make wax duplicates from a mold and I have the expertise to make a mold for the duplicates, but I too may very well have the same problem producing the duplicates myself given the thin and low relief sections involved, that your experts have experienced.
At this point I don't have any idea of the cost of having the waxes 3D printed. When I find that out that may very well solve a lot of the problems involved. Maybe that might solve your problem also.
In any case, I don't intend to thwart any of your effort on this project, since, as you may know, many of my projects just never seem to come to an end result that anyone can utilize.
Another point you need to consider, Myles, is that if your experts have made a silicon mold off your original latch member, the end result is going to be about 3 percent too small. I wonder how they might have adjusted for the shrinkage.
Jerry,
My understanding of the process they were trying to use is thus:
1 - Create silicon mould from part (incproprating the additional material I had attached).
2 - Use the silicom moulld to create a wax replica of the part.
3 - Surround wax part in sand, pour in alloy and the wax vacates the space leaving a replica part in the sand.
I was told to expect around 1% shrinkage which is sub-millimeter and I considered sub-critical. I had planned on measuring up the first trial pair to confirm dimensions were acceptable and consistent.
I am still trying to get alternaitve options out of them but am small-fry so patience is somewhat necessary.
Finally an update:
The first company I approached tried but was unable to reproduce the latch.
I have located another company that is going to produce 'die tooling' and cast the latch in stainless steel. I will still incorporate the additional material to beef up the strength, although this is probably not necessary given the greater strength of a stainless unit over stock.
Price estimate of $US220 - $US250 still, depending on number of units, freight, export & powdercoating costs & exchange rate.
I finally have ten black powder coated replacement latches in 316 stainless steel in my possession.
The one on the left is blank. The one on the right assembled with an old lock, cover, snib and pin. I have done this with all of them to check fit.
I will contact Roger at 928'sRus and arrange to send them through to him for his appraisal and subsequent on-sale. I will also let him know who has priority of supply based on this thread.
I will post asking price once I have figured that out and discussed with Roger.
Very nice job! My original cracked and it took a year before 928 Intl found me a used one that was not already cracked. I'm gentle with it. Don't slam the hatch and put as little pressure as possible on the latch with the hatch bumpers.
09-01-2014, 04:33 AM
Progress Report
