I can’t seem to get my brooder more than 80 degrees in 40 degree weather I have a stock tank with wire cloth over the top and a 250w bulb. I need suggestions.
You are lucky to have such a nice stock tank for your brooder. That's the way all the local farm stores around here brood their chicks for sale. If I had a stock tank, I'd use it as a brooder too.
I used a tow behind garden cart as my brooder and I also used heat lamps. I get my chicks in the early spring, and the temps in my garage are also in the low 40F's that time of year. Here are some suggestions that I think may help you.
1) The sides of a typical stock tank are pretty high. Using a 2x4 on top of the stock tank and clamping the heat lamp on it is not a good idea, IMHO. First of all, it looks like the heat lamp is too high for the 40F temp outside to heat up the area under the light to about 95F. You need to get the lamp lower into the stock tank. What I have had very good luck with is using 2 chains to suspend my heat lamps above the bedding. I never trust the clamp on the heat lamp as they can work themselves off the board and drop down into the litter - possible fire hazard. I use 2 chains to suspend the heat lamp because if one chain would fail, there is a backup to prevent the heat lamp from falling into the litter and starting a fire. Using chains makes it very easy to adjust the height of the heat lamp.
2) I always used 2 heat lamps for those first critical days and weeks because if one heat lamp fails, the chicks can still run under the other light for the night and keep warm. As you can tell, I am a big believer in backups. If one heat lamps fails, and if the temp in your brooder drops down to that 40F temp, you risk losing your chicks. I sleep better at night knowing that I have a backup heat lamp in case one bulb fails.
3) I would not use any towel anywhere near my heat lamps - fire hazard that I don't want to think about.
4) I have always had good luck with heat lamps over 20 years and if you secure them with chains, I believe they are safe. I like being able to look down into the brooder and see if the chicks are huddled together under the light (too cold), if the chicks won't go under the light at all (too warm), or if the chicks are running all around in and out of the light as needed (just right). I have not used the heat pads/tents/etc... that are out on the market now because I don't like not being able to see how the chicks are doing under the pad. I know many people have great things to say about those devices, but there are also many people here on BYC forums that have lost many chicks using those pads/tents and have no idea why. After using heat lamps over 30 years successfully, I doubt I'll change my ways.
5) You have a great setup for a chick brooder and I think with a few minor adjustments you will get the heat to your desired temps, safely, with the heat lamp(s).