Use of epoxy for levelling

[Rich]

Thanks Silyavski, its good to have all the detail laid out like that.

When thinking about the issue last night, I had in mind UK conditions and the tendency, recorded within various logs, to complete this task at below 25oC i.e. circa 10oC. This is relevant because as a general rule of thumb, a 5 degree F increase in cure temperature will half the time taken to cure, which is a thought I'd like to carry forward.

Per Jonathan's data, the suggestion must be that even with careful construction and preparation, the process retains a relatively high error rate, when compared to the required outcome. My addition is to suggest that the impact of the error rate, regardless of cause, could be halved by taking a two pour approach. I think that's relatively sound logic. But that not good enough.

However, as per the original posts #1, it took 72 hours to reach a state whereby it was possible to mark the epoxy using a finger nail i.e. the epoxy was still in a very plastic state at this time. So I am thinking, is this not the time to be thinking about mounting the rail?

The sort of procedure I have in mind is detailed below, but then I don't know how long it takes to mount the rail accurately? How much tinker time is needed?

Broad brush, the process would be as follows:

- Set up a bench test for the epoxy you are using. Dam an off-cut from the material used to make the supporting axis, circa 30cm in length?

- Before testing the epoxy, measure the ambient temperature, it needs to be below the manufacturers recommended cure temp, let say 15oC instead of 25oC. This provides for a much long gel and cure time.

- Mix and pour. One layer or two, depending on your view.

- Measure the hardness of the epoxy at regular intervals during the cure. A cure schedule can be drawn up based on the manufacturer specs in any event. Once it becomes evident that a thumb print can be made, start measuring the hardness of the cure by dropping a ball bearing from the same height and recording the difference in the diameter of the depression made.

- At a point to be determined by the dropping of the ball bearing i.e. while the epoxy is still relatively plastic, seat the rail using pre-drilled placement holes.

- There is where there is a balance to be struck, or not, depending on tinker time and ambient temperature. The rail needs to be seated on epoxy that is able to resist the the weight of the rail, but unable to resist seating of the rail when lightly bolted into place i.e. such that there is insufficient upward force to cause a deflection in the rail at the mid-point, between the two bolts.

Clearly it would help to run this experiment a few times. Removing a test sample isn't an issue.

Silyavski,
Like you clearly suggest, the right epoxy system is key. I would be concerned about using the West System if the ambient temperature is above 25 degrees C. Mixing - don't just stir the components together, mix the top into the bottom. Acetone will affect the chemistry of the resin system, so clean the frame well before the dam is constructed. Personally, I would do any final wipe using IPA. Heating/Degassing ... don't mix bubbles in. I wouldn't put a heat gun near epoxy, random application of heat? Use a brush and wet out the steel - like they did in the video. If you must, use a hair dryer set at min heat until you have a level. Heat the resin as a whole should you need to lower its viscosity prior to pouring. A water bath is the safest method - just be sure to dry the cup, as water and liquid epoxy need to be kept apart. Has anyone used a syringe to transfer the epoxy into the dam - 100ml every 40 cm or so?