Homemade Coil Skidplate

[Lesgold]

Hi Folks,

Just did a bit of research into the cost of a skid plate for a newly purchased coil. As it was only 8” in diameter, I assumed that the plates would be quite cheap because when you think about it, they are only glorified ice cream container lids. When I found that another kidney would need to be sold to fund the purchase, I decided that there must be a better way. Now this may end up as a total failure but I’m sure that many of you have tried and had some success. I reckon the wizards out there with 3D printers could come up with something or people who work in industry and have access to vacuum formers would be able to construct them with very little effort but in my case, I would like to use what I have in my own workshop and hope that something could be made to produce these throw away items. Logic tells me that a thermoplastic of some sort would be the obvious choice to use as it can be softened by heat and moulded in some way. If I could come up with a technique, the best choice of material would be determined later. After thinking about it for a while, I decided that a plug and ring mould might be a good option for making the skid plates. If I could accurately machine these components and then press some plastic into shape, there is a possibility that a reasonable plate could be made. I made a start this morning by making a plug. A piece of 16mm MDF was cut into a disc and machined to size on the wood lathe.

it was turned down in diameter until it was a tight fit onto the skid plate that I already had.

Some extra MDF was then cut and glued to make the ring mould. 

When the glue dries, the ring mould will be mounted on a face plate and machined so that the plug will sit inside with an allowance for skid plate wall thickness. I decided to make the depth of the recess a bit over 20mm. The deformation of the plastic as it’s pushed into shape will create problems so I decided to add the extra depth so that surplus could be cut off later. When I was teaching, the kids and I used to make moulds for acrylic using this technique and we found that the compression and expansion forces involved created all sorts of issues unless tolerances were right. I’ll get back to the turning tomorrow morning.

[Ridge Runner]

I always say nothing ventured nothing gained. 
 
Best of luck on the outcome.

 Chuck 

[Lesgold]

Thanks Chuck. I’ve got nothing to lose except a bit of time and a few dollars. It’s raining here and I can’t be out prospecting so I may as well do something even if it means at the end of the day it was a waste of time. At least I’ll learn something.

[phrunt]

1 hour ago, Lesgold said:

Thanks Chuck. I’ve got nothing to lose except a bit of time and a few dollars. It’s raining here and I can’t be out prospecting so I may as well do something even if it means at the end of the day it was a waste of time. At least I’ll learn something.

If you have success, you could start selling them! 

I really like people doing stuff themselves, the learning, the benefits of doing so and the feeling of the success when you get the job done.  Well done so far.

The original ones come in two types, the white ones that I have no idea what plastic they are, and heavy duty ones that are more transparent which are polycarbonate.  I have fixed an original white one that was bent in shipping with its boxed crushed by using a hair dryer.  

[dig4gold]

What about fibreglass?

D4G

[Lesgold]

I suppose you could use fibreglass. It would be a simple task to make a mould using the lathe. It would be interesting to see how a skid plate would wear over time with glass fibres being exposed as the resin wears away. The resin itself is a bit brittle and may chip in use. Not sure on that one to be honest. I do know that I hate working with the stuff. 

[Lesgold]

I was keen to finish making the female section of the mould so I got up early and mounted the blank to a faceplate. The shaping only took about ten minutes. MDF machines easily with lathe tools. 

The internal diameter was made slightly larger than the diameter of the plug. This was done to allow for the wall thickness of the skid plate. I will fine tune the size when I know the thickness of the plastic that will be used. You may also notice that the leading edge of the mould was chamfered and then rounded slightly with abrasive paper. This will hopefully allow the soft plastic to form into the mould gently without grabbing on a sharp edge. I drilled a few holes through the base to allow air to escape and also to provide a few areas where the skid plate could be knocked out of the mould from the back.

That’s basically all I need. The plug that I made yesterday will be forced into the mould using the tail stock of the lathe to apply pressure. I may also have to use G cramps to force the soft plastic into shape. I’m not exactly sure as to how much pressure will be needed until I get to the next step. It’s Sunday morning here so the shops will be closed. I may have to buy some plastic sheeting online but I do have an idea in relation to using some PVC pipe for the experiment. I’ll have a play after breakfast to see what can be done.

[Lesgold]

I cut an old piece of PVC storm water pipe that would be good enough for a project test.

It has a diameter of 90mm and a wall thickness of 2mm. Unfolded, it would give me more than enough material for the test plate but its thickness is just a fraction more than what I’d hoped for. The standard skid plate is 1.5mm thick so I will end up with a slightly heavier result. I’m hoping it won’t impact on how it fits or its performance but time will tell. A jig saw was used to cut the pipe down its length. It was surprisingly simple and only took 5 seconds to complete.

A heat gun was used to warm the PVC and and slowly bend it out to a reasonably flat sheet.

I began heating along the length of the pipe on the opposite side to the cut and this then allowed the PVC to be opened out into a sort of “M” shape. Heat was then applied evenly over the material until it sat reasonably flat.

This process took a few minutes to achieve. A circle was then cut out to a diameter slightly larger than what was needed. The material was also given a bit of a clean.

Three screws were placed into the ring mould to position the blank and allow it to be heated. Keeping an air gap helped to prevent a heat sink situation from forming.

The hot air gun was then used to heat the entire blank before the plug was pushed into place using the lathes tailstock centre. Cramps were then applied to force the plug further into the mould. The heat gun was used to continually apply extra heat to the tag ends of blank as pressure was applied. You can see the corrugated effect that resulted on the outer edge of the blank.

[phrunt]

It looks like you've done it, I guess you could use one of them multi tools to cut the overhanging stuff off before removing it from the mold? 

[Lesgold]

The corrugated tag ends provided an area where pliers could be used to extract the skid plate from the mould. I expected this to be a difficult task as no release angles were placed on either the plug or ring sections of the mould. By moving my way around the mould, the skid plate pulled out without too much effort. The end result showed some promise.

The plug was locked into the skid plate due to the corrugations but I thought that this problem could be solved by trimming surplus material using a lathe tool. The ring mould was screwed back onto the lathe and an off cut of material acted to pad the recess. The plug was held in place with the tailstock centre and a parting tool was used to cut the waste away.

The skid plate was then removed from the plug.

The skid plate was returned to the lathe so that it could be trimmed to the exact height required. When this was achieved, the final test was to see how it fitted to the coil. I was actually surprised as to how well it slipped into place. I think there was a bit of luck involved here as it was a good, tight fit. I reckon I could use the plate without tape. 

Some tape was applied and the job was done. Looks like it may work quite well. Testing will indicate if the PVC is too brittle and it will be interesting to see how it wears. I may try some polycarbonate in the future to see how it compares. These moulds could be made easily with just a jig saw and a few cramps. Accuracy of saw cuts would determine success if this process was used. I’ll give some feedback in the future as to how the skid plate works.

Cheers

Les